Abstract

The article aims to estimate the incidence and worsening of back pain (BP) during the first wave of COVID-19 in Brazil, as well as to investigate demographic, socioeconomic factors and associated changes in living conditions. ConVid - Behavior Research, applied between April and May 2020, was used as data source. The number and distribution of respondents who developed BP and those who had a worsening of the preexisting problem, their 95% confidence intervals and Pearson’s Chi-square test were estimated. The odds ratio of developing BP or worsening a preexisting problem was also estimated using multiple logistic regression models. Pre-existing BP was reported by 33.9% (95%CI 32.5-35.3) of respondents and more than half (54.4%; 95%CI 51.9-56.9) had worsened. The cumulative incidence of BP in the first wave of the pandemic was 40.9% (95%CI 39.2-42.7). Being a woman, the perceived increase in housework and the frequent feeling of sadness or depression were associated with both outcomes. Socioeconomic factors were not associated with any of outcome. The high incidence and worsening of BP during the first wave reveal the need for studies in more recent periods, given the long duration of the pandemic.

Key words:
COVID-19; Spine; Health inequalities

Introduction

The COVID-19 pandemic began in the first quarter of 2020 and quickly spread, leading to more than 6 million deaths worldwide¹1 Ritchie H, Mathieu E, Rodés-Guirao L, Appel C, Giattino C, Ortiz-Ospina E, Gavrilov D, Hasell J, Macdonald B, Dattani S, Beltekian D, Roser M. Coronavirus Pandemic (COVID-19) [Internet]. Our World in Data. 2020. [cited 2022 mar 28]. Available from: https://ourworldindata.org/covid-deaths
https://ourworldindata.org/covid-deaths... , including 658,000 deaths in Brazil²2 Fundação Oswaldo Cruz (Fiocruz). Instituto de Comunicação e Informação Científica e Tecnológica em Saúde (ICICT). MonitoraCovid-19 [Internet]. 2020. [citado 2022 mar 28]. Disponível em: https://bigdata-covid19.icict.fiocruz.br/
https://bigdata-covid19.icict.fiocruz.br... . In addition to the alarming number of deaths, a wide range of indirect effects of the sanitary crisis impacted the Brazilian population. The loss of jobs, the decline in income levels³3 Almeida WS, Szwarcwald CL, Malta DC, Barros MBA, Souza PRB, Azevedo LO, Romero D, Lima MG, Damacena GN, Machado IE, Gomes CS, Pina MF, Gracie R, Werneck AO, Silva DRP. Mudanças nas condições socioeconômicas e de saúde dos brasileiros durante a pandemia de COVID-19. Rev Bras Epidemiol 2021; 23:E200105., a worsening of mental health⁴4 Barros MBA, Lima MG, Malta DC, Szwarcwald CL, Azevedo RCS, Romero D, Souza Júnior PRB, Azevedo LO, Machado IE, Damacena GN, Gomes CS, Werneck AO, Silva DRPD, Pina MF, Gracie R. Relato de tristeza/depressão, nervosismo/ansiedade e problemas de sono na população adulta brasileira durante a pandemia de COVID-19. Epidemiol Serv Saude 2020; 29(4):e2020427.^,55 Malta DC, Gomes CS, Szwarcwald CL, Barros MBA, Silva AG, Prates EJS, Machado IE, Souza Júnior PRB, Romero D, Damacena GN, Azevedo LO, Pina MF, Werneck AO, Silva DRP. Distanciamento social, sentimento de tristeza e estilos de vida da população brasileira durante a pandemia de COVID-19 [Internet]. 2020. [citado 2021 abr 13]. Disponível em: https://preprints.scielo.org/index.php/scielo/preprint/view/1371/version/1465
https://preprints.scielo.org/index.php/s... , and negative changes in the population’s lifestyles⁶6 Silva DRPD, Werneck AO, Malta DC, Souza Júnior PRB, Azevedo LO, Barros MBA, Szwarcwald CL. Changes in the prevalence of physical inactivity and sedentary behavior during COVID-19 pandemic: a survey with 39,693 Brazilian adults. Cad Saude Publica 2021; 37(3):e00221920.

7 Silva DR, Werneck AO, Malta DC, Souza-Júnior PRB, Azevedo LO, Barros MBA, Szwarcwald CL. Incidence of physical inactivity and excessive screen time during the first wave of the COVID-19 pandemic in Brazil: what are the most affected population groups? Ann Epidemiol 2021; 62:30-35.

8 Malta DC, Gomes CS, Barros MBA, Lima MG, Almeida WDS, Sá ACMGN, Prates EJS, Machado ÍE, Silva DRPD, Werneck AO, Damacena GN, Souza Júnior PRB, Azevedo LO, Montilla DER, Szwarcwald CL. Noncommunicable diseases and changes in lifestyles during the COVID-19 pandemic in Brazil. Rev Bras Epidemiol 2021; 24:e210009.^-99 Werneck AO, Silva DRD, Malta DC, Souza-Júnior PRB, Azevedo LO, Barros MBA, Szwarcwald CL. Lifestyle behaviors changes during the COVID-19 pandemic quarantine among 6,881 Brazilian adults with depression and 35,143 without depression. Cien Saude Colet 2020; 25(Suppl. 2):4151-4156. have been confirmed due to the lack of an adequate social and economic support in a scenario of strong economic crisis³3 Almeida WS, Szwarcwald CL, Malta DC, Barros MBA, Souza PRB, Azevedo LO, Romero D, Lima MG, Damacena GN, Machado IE, Gomes CS, Pina MF, Gracie R, Werneck AO, Silva DRP. Mudanças nas condições socioeconômicas e de saúde dos brasileiros durante a pandemia de COVID-19. Rev Bras Epidemiol 2021; 23:E200105. and the restriction of physical and social contact¹⁰10 Szwarcwald CL, Souza Júnior PRB, Malta DC, Barros MBA, Magalhães MAFM, Xavier DR, Saldanha RF, Damacena GN, Azevedo LO, Lima MG, Romero D, Machado ÍE, Gomes CS, Werneck AO, Silva DRPD, Gracie R, Pina MF. Adherence to physical contact restriction measures and the spread of COVID-19 in Brazil. Epidemiol Serv Saude 2020; 29(5):e2020432..

Epidemiological studies conducted in the periods prior to the pandemic demonstrated that back problems (BP) are associated with socioeconomic, demographic, and occupational conditions, as well as to lifestyle and mental health¹¹11 Hoy D, Brooks P, Blyth F, Buchbinder R. The epidemiology of low back pain. Best Pract Res Clin Rheumatol 2010; 24(6):769-781.

12 Bento TPF, Genebra CVS, Maciel NM, Cornelio GP, Simeão SFAP, Vitta A. Low back pain and some associated factors: is there any difference between genders? Braz J Phys Ther 2020; 24(1):79-87.

13 Dionne CE, Dunn KM, Croft PR. Does back pain prevalence really decrease with increasing age? A systematic review. Age Ageing 2006; 35(3):229-234.

14 Govindu NK, Babski-Reeves K. Effects of personal, psychosocial and occupational factors on low back pain severity in workers. Int J Industrial Ergonomics 2014; 44(2):335-341.

15 Malta DC, Oliveira MM, Andrade SSCA, Caiaffa WT, Souza MFM, Bernal RTI. Fatores associados à dor crônica na coluna em adultos no Brasil. Rev Saude Publica 2017; 51(Supl. 1):9s.

16 Hurwitz EL, Morgenstern H, Yu F. Cross-sectional and longitudinal associations of low-back pain and related disability with psychological distress among patients enrolled in the UCLA Low-Back Pain Study. J Clin Epidemiol 2003; 56(5):463-471.

17 Romero DE, Santana D, Borges P, Marques A, Castanheira D, Rodrigues JM, Sabbadini L. Prevalence, associated factors, and limitations related to chronic back problems in adults and elderly in Brazil. Cad Saude Publica 2018; 34(2):e00012817.^-1818 Andrade FCD, Chen XS. A biopsychosocial examination of chronic back pain, limitations on usual activities, and treatment in Brazil, 2019. PLoS One 2022; 17(6):e0269627.. The evidence shows that BPs tend to more commonly affect the populations with lower income¹⁸18 Andrade FCD, Chen XS. A biopsychosocial examination of chronic back pain, limitations on usual activities, and treatment in Brazil, 2019. PLoS One 2022; 17(6):e0269627. and education levels¹¹11 Hoy D, Brooks P, Blyth F, Buchbinder R. The epidemiology of low back pain. Best Pract Res Clin Rheumatol 2010; 24(6):769-781.^,1515 Malta DC, Oliveira MM, Andrade SSCA, Caiaffa WT, Souza MFM, Bernal RTI. Fatores associados à dor crônica na coluna em adultos no Brasil. Rev Saude Publica 2017; 51(Supl. 1):9s.^,1717 Romero DE, Santana D, Borges P, Marques A, Castanheira D, Rodrigues JM, Sabbadini L. Prevalence, associated factors, and limitations related to chronic back problems in adults and elderly in Brazil. Cad Saude Publica 2018; 34(2):e00012817.^,1818 Andrade FCD, Chen XS. A biopsychosocial examination of chronic back pain, limitations on usual activities, and treatment in Brazil, 2019. PLoS One 2022; 17(6):e0269627., of an older age¹³13 Dionne CE, Dunn KM, Croft PR. Does back pain prevalence really decrease with increasing age? A systematic review. Age Ageing 2006; 35(3):229-234.^,1515 Malta DC, Oliveira MM, Andrade SSCA, Caiaffa WT, Souza MFM, Bernal RTI. Fatores associados à dor crônica na coluna em adultos no Brasil. Rev Saude Publica 2017; 51(Supl. 1):9s., of the female gender¹²12 Bento TPF, Genebra CVS, Maciel NM, Cornelio GP, Simeão SFAP, Vitta A. Low back pain and some associated factors: is there any difference between genders? Braz J Phys Ther 2020; 24(1):79-87., with infrequent physical exercise¹⁵15 Malta DC, Oliveira MM, Andrade SSCA, Caiaffa WT, Souza MFM, Bernal RTI. Fatores associados à dor crônica na coluna em adultos no Brasil. Rev Saude Publica 2017; 51(Supl. 1):9s., and who show symptoms of depression¹⁶16 Hurwitz EL, Morgenstern H, Yu F. Cross-sectional and longitudinal associations of low-back pain and related disability with psychological distress among patients enrolled in the UCLA Low-Back Pain Study. J Clin Epidemiol 2003; 56(5):463-471..

When the BPs appear as continuous pain for three months or more, this is generally defined as a chronic condition, although there is no clear consensus on the reference period to determine chronicity¹⁹19 Meucci RD, Fassa AG, Faria NMX. Prevalence of chronic low back pain: systematic review. Rev Saude Publica 2015; 49:73.. In addition, other studies use different criteria to define chronicity, such as pain and the possible limitations resulting from this condition²⁰20 Cedraschi C, Robert J, Goerg D, Perrin E, Fischer W, Vischer TL. Is chronic non-specific low back pain chronic? Definitions of a problem and problems of a definition. Br J Gen Pract 1999; 49(442):358-362.. In Brazil, the nationwide studies have used the National Health Survey (NHS) as a source of information on the theme¹⁵15 Malta DC, Oliveira MM, Andrade SSCA, Caiaffa WT, Souza MFM, Bernal RTI. Fatores associados à dor crônica na coluna em adultos no Brasil. Rev Saude Publica 2017; 51(Supl. 1):9s.^,1717 Romero DE, Santana D, Borges P, Marques A, Castanheira D, Rodrigues JM, Sabbadini L. Prevalence, associated factors, and limitations related to chronic back problems in adults and elderly in Brazil. Cad Saude Publica 2018; 34(2):e00012817.^,1818 Andrade FCD, Chen XS. A biopsychosocial examination of chronic back pain, limitations on usual activities, and treatment in Brazil, 2019. PLoS One 2022; 17(6):e0269627.^,2121 Romero DE, Muzy J, Maia L, Marques AP, Souza Júnior PRB, Castanheira D. Chronic low back pain treatment in Brazil: inequalities and associated factors. Cien Saude Colet 2019; 24(11):4211-4226.. In the NHS, chronic back problems (CBP) is evaluated by means of a self-reported diagnosis and the questions used for measurement do not define the period when the pain occurred.

According to NHS data from 2019, the prevalence of the CBP among Brazilian adults was of 23.4%¹⁸18 Andrade FCD, Chen XS. A biopsychosocial examination of chronic back pain, limitations on usual activities, and treatment in Brazil, 2019. PLoS One 2022; 17(6):e0269627.. By contrast, the study conducted in the city of São Paulo between 2016 and 2018 demonstrates that 6 in every 10 individuals have already had some type of BP at some point in their lives, though not necessarily CBP²²22 Gonzalez GZ, da Silva T, Avanzi MA, Macedo GT, Alves SS, Indini LS, Egea LMP, Marques AP, Pastre CM, Costa LDCM, Costa LOP. Low back pain prevalence in Sao Paulo, Brazil: a cross-sectional study. Braz J Phys Ther 2021; 25(6):837-845.. Although CBP is not potentially fatal, it does represent one of the main reasons for doctors’ appointments²³23 Dagenais S, Caro J, Haldeman S. A systematic review of low back pain cost of illness studies in the United States and internationally. Spine J 2008; 8(1):8-20. and years lost due to disability²⁴24 Hoy D, March L, Brooks P, Blyth F, Woolf A, Bain C, Williams G, Smith E, Vos T, Barendregt J, Murray C, Burstein R, Buchbinder R. The global burden of low back pain: estimates from the Global Burden of Disease 2010 study. Ann Rheum Dis 2014; 73(6):968-974.^,2525 David CN, Deligne LMC, Silva RS, Malta DC, Duncan BB, Passos VMA, Cousin E. The burden of low back pain in Brazil: estimates from the Global Burden of Disease 2017 Study. Popul Health Metrics 2020; 18(Suppl. 1):12..

The increase in reports and aggravations of BP during the pandemic has been shown in international studies²⁶26 Fiok K, Karwowski W, Gutierrez E, Saeidi M, Aljuaid AM, Davahli MR, Taiar R, Marek T, Sawyer BD. A study of the effects of the COVID-19 pandemic on the experience of back pain reported on Twitter(r) in the United States: a natural language processing approach. Int J Environ Res Public Health 2021;18(9):4543.^,2727 Šagát P, Bartík P, Prieto González P, Tohănean DI, Knjaz D. Impact of COVID-19 quarantine on low back pain intensity, prevalence, and associated risk factors among adult citizens residing in Riyadh (Saudi Arabia): a cross-sectional study. IJERPH 2020; 17(19):7302.. However, there were no reliable nationwide sources available about how the COVID-19 pandemic affected BP in the Brazilian population. In this sense, a survey was conducted in Brazil concerning the living conditions before and after the first wave of the pandemic²⁸28 Szwarcwald C, Souza-Júnior P, Damacena G, Malta D, Barros M, Romero D, Almeida WDS, Azevedo LO, Machado ÍE, Lima MG, Werneck AO, Silva DRPD, Gomes CS, Ferreira APS, Gracie R, Pina MF. ConVid - Pesquisa de Comportamentos pela Internet durante a pandemia de COVID-19 no Brasil: concepção e metodologia de aplicação. Cad Saude Publica 2021; 37(3):e00268320., which includes questions concerning BP.

The present study aimed to estimate the incidence of BP and the aggravation (worsening) of CBP during the first wave of COVID-19 in Brazil, as well as investigate the demographic and socioeconomic factors, together with the changes in the associated living conditions.

Methods

Data source

This study’s data source was ConVid - Behavioral Study, a health survey conducted nationwide by the Oswaldo Cruz Foundation, in partnership with Universidade Federal de Minas Gerais (UFMG) and Universidade Estadual de Campinas (UNICAMP), during the period of social distancing due to the COVID-19 pandemic. The project was approved by the National Research Ethics Commission (CONEP, in Portuguese) on April 19, 2020, logged under protocol number 3.980.277. The survey was applied between April 24 and May 24, 2020, by a self-completed online questionnaire, by cell phone or by computer with access to the internet. All of the answers were anonymous and are stored in the server from the Institute of Communication and Scientific and Technological Information in Health (ICICT/FIOCRUZ). To participate in the study, the individual must be 18 years of age or older when completing the questionnaire and have resided in Brazil during the COVID-19 pandemic.

Sample

Sampling was performed using the “virtual snowball” method, by sending invitations to complete the electronic questionnaire through social medias. The final size of the sample reached 45,161 people after stratification. This sample was calibrated by means of the data from the National Household Sample Survey (PNAD, in Portuguese), from the Brazilian Institute of Geography and Statistics (IBGE, in Portuguese) in order to obtain the same distribution by state, sex, age group, race/color, and level of education of the Brazilian population. Further details on the ConVid - Behavioral Study can be found in the publication of the methodology²⁸28 Szwarcwald C, Souza-Júnior P, Damacena G, Malta D, Barros M, Romero D, Almeida WDS, Azevedo LO, Machado ÍE, Lima MG, Werneck AO, Silva DRPD, Gomes CS, Ferreira APS, Gracie R, Pina MF. ConVid - Pesquisa de Comportamentos pela Internet durante a pandemia de COVID-19 no Brasil: concepção e metodologia de aplicação. Cad Saude Publica 2021; 37(3):e00268320., as well as on the internet research page (https://convid.fiocruz.br/).

Outcome variables

Initially, the pre-existence of CBP was defined by the affirmative answer (yes/no) to the following questions: “Do you have some type of chronic back problem, such as chronic pain in your back or neck, low back pain, sciatica pain, problems in the vertebrae or disc?” Among those who reported not having BP prior to the pandemic, the cumulative incidence of BP during the pandemic was evaluated by the following question: “During the pandemic, with the changes in your day-to-day activities, did you begin to feel some type of pain in your back or your spine?” The answer choices were: (a) yes, a little; (b) yes, a lot; and (c) no. The answers “a” and “b” were considered for the definition of the presence of the outcome. Among those who reported having a problem prior to the pandemic, the aggravation of the CBP during the pandemic was evaluated by the following question: “During the pandemic, did the changes in your day-to-day activities affect your back pain?” The answer choices were: (a) remained the same; (b) increased a little; (c) increased a lot; and (d) diminished. The answers “b” and “c” were considered for the outcome.

Exposure variables

The unmodifiable socioeconomic and demographic variables due to the pandemic that were considered in this study were: sex (female and male), age group (18-29; 30-49; 50-59; 60 years or older); pre-pandemic household per capital income (< 1 minimum salary (MS), 1-2 MS, 2-4 MS, and >= 4 MS); level of education (complete elementary education or less, complete secondary education, complete higher education or more); and race/color, categorized as white and “non-white”, which consists of the combination of the following categories: black, yellow, brown, and indigenous.

This study also used the variables concerning socioeconomics, health, and living conditions that may have changed due to the pandemic. The physical exercise variable (stopped doing, reduced, increased, or maintained) was created through the original variables: “Before the new coronavirus pandemic, how many days a week did you do some type of physical exercise or practice a sport?” and “During the new coronavirus pandemic, how many days a week do you/did you do physical exercise or practice a sport?”

The answers to the variables were recoded: self-assessment of health (regular, poor, or terrible; good; excellent); housework (increased a lot, increased a little, remained the same, or diminished); and felt sad or depressed (many times or always; few times; never); and the impact of the pandemic on income (diminished a lot or went without income, diminished a little, increased or remained the same). The variable of work during the pandemic was obtained through the recategorization of the answers to the question: “How did the pandemic affect your occupation/work?” The categories “paid vacation”, “lost my job”, and “I went without work” were added to “stopped working”, while the categories “continued working” and “began to work after the pandemic” composed the new category of “worked outside the home”. The categories of “continued to work” and “worked at home” remained the same.

Analysis

This study estimated the number and the distribution of participants who developed BP (cumulative incidence) and who had an aggravation (worsening) of the pre-existing problem (CBP), with the respective 95% confidence interval (95%CI), according to the described exposure variables. The distributions took into account the sample weighting. To verify the association between the observed characteristics and the outcomes, Pearson’s chi-square test was used, and the respective p-values were presented. Additionally, the average age of the people who developed or who suffered a worsening of BP were estimated, whose distribution was normal. It is important to note that the cumulative incidence was calculated in a retrospective manner, given the cross-sectional design of this study.

The odds ratio (OR) to develop BP or suffer a worsening of the pre-existing condition was estimated, together with their respective 95%CI, through multiple logistic regression models in two hierarchical levels: the first considering factors that are not affected by the pandemic and the second incorporating the possible effects of the same. The analyses were carried out using the Statistical Package for the Social Sciences (SPSS), version 21, taking into consideration the sample weight obtained for the calibration of the sample.

Results

In all, this study received 45,161 answers after weighting and, of these, 44,836 answered the questions about BP (Figure 1). The pre-existing CBP was reported by 33.9% (95%CI 32.5-35.3) of the participants (n = 15,194) and more than half (54.4%; 95%CI 51.9-56.9) reported a worsening of the medical condition (n = 8,263). Of those that had not had BP before (n = 29,642), 40.9% (95%CI 39.2-42.7) began to have BP during the pandemic (n = 12,133). The participants who developed BP or who suffered a worsening of the condition due to the pandemic, were 45.2% (95%CI 43.7-46.6) of the total sample (n = 20,396).

The cumulative incidence of BP during the pandemic was greater for women, when compared to men (48.7%; 95%CI 46.8-50.6 and 33.7%; 95%CI 30.9-36.6, respectively). This was also higher among younger individuals, especially in the age groups of 18 to 29 years (48.3%; 95%CI 45.4-51.2) and 30 to 49 years (42.6%; 95%CI 39.6-45.7). The average age of the individuals who developed BO was 38 years. As regards the socioeconomic variables, people with a lower household per capita income (< 1 MS) before the pandemic, presented a higher cumulative incidence of BP than did those of the other groups (44.7%; 95%CI 42.0-47.4) (Table 1).

The living conditions affected during the pandemic also influenced the cumulative incidence of BP. People who stopped doing physical exercise presented higher incidences (47.4%; 95%CI 44.0-50.9) than those who reduced their physical exercise (36.6%; 95%CI 31.7-41.8) or who increased/maintained the frequency (39.2%; 95%CI 37.0-41.5). Those who assessed their health as regular/poor/terrible presented almost twice the incidence of BP, as compared to those with an excellent self-assessment of health (53.6%; 95%CI 49.2-58.0 and 29.1%; 95%CI; 26.0-32.5, respectively) (Table 1).

Individuals who reported a significant increase in housework (52.7%; 95%CI 48.7-56.7) presented a cumulative incidence of BP that was higher than those who remained the same or reduced their housework (31.5%; 95%CI 28.9-34.2). Among those who reported feeling sad or depressed many times or always, one in every two began to have BP (53.9%; 95%CI 50.9-56.8), a proportion twice that of those who reported never having felt this way (25.0%; 95%CI 21.2-29.3) (Table 1).

People who reported an increase in or who were able to maintain their income level presented a lower cumulative incidence of BP (36.8%; 95%CI 34.5-39.2) as compared to those who had a minimal (43.8%; 95%CI 40.6-47.0) or high reduction in income (43.2%; 95%CI 39.6-46.9). Individuals who worked outside the home presented a lower cumulative incidence of BP (33.0%; 95%CI 29.5-36.6) when compared to the other categories (Table 1).

Six in every ten women reported a worsening of CBP during the pandemic, while for men, this relation was four in every ten (61.5%; 95%CI; 58.8-64.1 and 41.9%; 95%CI 37.2-46.7, respectively). The age, though with less significant differences, showed that older people (49.8%; 95%CI 44.5-55.0) had a slightly lower proportion than the other age groups. The average age of the individuals who showed a worsening was of 46 years. Individuals with a higher level of education showed a higher proportion of the worsening of BP during the pandemic (62.3%; 95%CI 61.2-63.4) (Table 2).

The worsening of CBP was more significant among those who reduced their practice of physical exercise (63.2%; 95%CI 55.4-70.4), people with a regular/poor/terrible self-assessment of health (63.7%; 95%CI 59.5-67.7), a major increase in housework (69.4%; 95%CI 65.2-73.4), and among those who suffered from a frequent feeling of sadness or depression (65.6%; 95%CI 62.0-69.0). In relation to work, a greater proportion of people who continued to work from home showed a worsening in CBP (61.3%; 95%CI 56.9-65.5) as compared to the other categories.

In the first stage of the model (Table 3), women presented a 31% greater chance of developing BP (OR 1.31; 95%CI 1.14-1.51), while in the second stage, they presented an 18% greater chance (OR 1.18; 95%CI 1.01-1.38). Young people, aged 18 to 29 years, presented a 3-fold higher chance of developing BP in both stages, when compared to older people (60 years or older) (OR 3.21; 95%CI 2.51-4.10, OR 2.73; 95%CI 2.11-3.53, respectively).

In the second stage of the model of cumulative incidence of BP (Table 3), considering the effect of the pandemic on living conditions, individuals who stopped doing physical exercise had a greater chance of developing BP (OR 1.23; 95%CI 1.05-1.45); increased their housework, be it a little (OR 1.38; 95%CI 1.18-1.63) or a lot (OR 1.35; 95%CI 1.11-1.64); suffered the feeling of sadness or depression, be it a few times (OR 1.27; 95%CI 1.00-1.61) or frequently (OR 1.50; 95%CI 1.17-1.93); worked from home (OR 1.48; 95%CI 1.20-1.82); and continued without work (OR 1.27; 95%CI 1.02-1.58).

Women presented a greater chance of worsening their BP, both in the first (OR 2.44; 95%CI 2.03-2.93) as well as in the second stages of the model (OR 1.87; 95%CI 1.55-2.26). The younger individuals (18-29 years) were the only age group that showed a significant difference to the older people, showing more accentuated results in the second stage of the model. When considering the living conditions during the pandemic, young individuals, aged 18 to 29 years, showed nearly 70% less chances to worsen a pre-existing BP (OR 0.32; 95%CI 0.24-0.43). To the contrary of regression, which considers the cumulative incidence, the older people had a greater chance of worsening the medical condition of CBP, regardless of other conditions (Table 4).

The regular/poor/terrible self-assessment of health implied a 3-fold greater chance of a worsening of CBP (OR 3.08; 95%CI 2.34-4.06), as compared to an excellent self-assessment. Those who presented an excellent self-assessment presented greater chances of a worsening of CBP (OR 1.65; 95%CI 1.29-2.11). The accentuated and mild increase in housework during the pandemic was associated with a worsening of CBP (OR 2.01; 95%CI 1.61-2.50 and OR 1.44; 95%CI 1.18-1.75, respectively). The feeling of sadness, be it a few times (OR 1.48; 95%CI 1.08-2.01) or frequently (OR 2.43; 95%CI 1.78-3.31), also increased the chances of a worsening of CBP.

Discussion

This study presented evidence of negative effects of the COVID-19 pandemic on the incidence and worsening of BP in the Brazilian population. Nevertheless, this impact occurred in an unequal manner. Being a woman, reporting an increase in housework, and feeling sad/depressed during the pandemic were factors associated with both outcomes. Being of younger age groups proved to be associated with the incidence of BP, while a worsening in the medical condition of CBP was associated with older-aged populations. Stopping physical exercise, continuing without work, or beginning to work from home during the pandemic were the changes in living conditions associated with the emergence of BP. The regular/poor/terrible self-assessment of health during the pandemic was associated only with the worsening of CBP. The socioeconomic factors did not prove to be associated with any of the analyzed outcomes.

In Saudi Arabia, one study conducted between March and April 2020 reported an increase in the intensity of BP among those who suffered from this medical condition, in addition to an increase in the reports of pain (incidence) during the study period²⁷27 Šagát P, Bartík P, Prieto González P, Tohănean DI, Knjaz D. Impact of COVID-19 quarantine on low back pain intensity, prevalence, and associated risk factors among adult citizens residing in Riyadh (Saudi Arabia): a cross-sectional study. IJERPH 2020; 17(19):7302.. Corroborating with the present study, the increase in the number of cases was associated with the changes in working conditions, especially in that referent to the generalization of “home office”, the diminishing of the level of physical exercise, and the increase in stress levels²⁷27 Šagát P, Bartík P, Prieto González P, Tohănean DI, Knjaz D. Impact of COVID-19 quarantine on low back pain intensity, prevalence, and associated risk factors among adult citizens residing in Riyadh (Saudi Arabia): a cross-sectional study. IJERPH 2020; 17(19):7302.. According to Sagat et al.²⁷27 Šagát P, Bartík P, Prieto González P, Tohănean DI, Knjaz D. Impact of COVID-19 quarantine on low back pain intensity, prevalence, and associated risk factors among adult citizens residing in Riyadh (Saudi Arabia): a cross-sectional study. IJERPH 2020; 17(19):7302., the restrictive measures and social distancing were responsible for changes in the way of life and individual behaviors that, consequently, raised the incidence and worsening of BP during the pandemic. Another study, conducted based on publications from Twitter in the USA demonstrated that, between November 2019 and November 2020, there was an 84% increase in reports of BP in social media²⁶26 Fiok K, Karwowski W, Gutierrez E, Saeidi M, Aljuaid AM, Davahli MR, Taiar R, Marek T, Sawyer BD. A study of the effects of the COVID-19 pandemic on the experience of back pain reported on Twitter(r) in the United States: a natural language processing approach. Int J Environ Res Public Health 2021;18(9):4543..

The higher incidence of BP or the worsening of CBP among women, observed in the present study, showed that the pandemic affected the different genders in a unequal manner. However, this inequality is not new to the pandemic, given that studies conducted in previous periods had already reported that BP more commonly affected women¹²12 Bento TPF, Genebra CVS, Maciel NM, Cornelio GP, Simeão SFAP, Vitta A. Low back pain and some associated factors: is there any difference between genders? Braz J Phys Ther 2020; 24(1):79-87.^,1717 Romero DE, Santana D, Borges P, Marques A, Castanheira D, Rodrigues JM, Sabbadini L. Prevalence, associated factors, and limitations related to chronic back problems in adults and elderly in Brazil. Cad Saude Publica 2018; 34(2):e00012817.. The explanation for such evidence appears in many ways in the literature, which presents from genetic and biological explanations, such as the musculoskeletal structure, menstruation, osteoporosis, and pregnancy²⁴24 Hoy D, March L, Brooks P, Blyth F, Woolf A, Bain C, Williams G, Smith E, Vos T, Barendregt J, Murray C, Burstein R, Buchbinder R. The global burden of low back pain: estimates from the Global Burden of Disease 2010 study. Ann Rheum Dis 2014; 73(6):968-974., to social explanations²⁹29 Dahlberg R, Karlqvist L, Bildt C, Nykvist K. Do work technique and musculoskeletal symptoms differ between men and women performing the same type of work tasks? Appl Ergon 2004; 35(6):521-529.^,3030 Strazdins L, Bammer G. Women, work and musculoskeletal health. Soc Sci Med 2004; 58(6):997-1005.. In the latter case, it is clear that, for cultural reasons, women end up taking on greater responsibility in the house and maternal work, which, at the same time, means a greater workload²⁹29 Dahlberg R, Karlqvist L, Bildt C, Nykvist K. Do work technique and musculoskeletal symptoms differ between men and women performing the same type of work tasks? Appl Ergon 2004; 35(6):521-529. and less free time to relax and exercise³⁰30 Strazdins L, Bammer G. Women, work and musculoskeletal health. Soc Sci Med 2004; 58(6):997-1005.. The social distancing measures kept people inside their houses for longer periods of time, and with this, many women found themselves obliged to concomitantly perform paid and unpaid work, a fact that caused a physical and psychological overload in this group³¹31 Power K. The COVID-19 pandemic has increased the care burden of women and families. Sustain Sci Pract Policy 2020; 16(1):67-73.. In this light, it is reasonable to assume that these were the most relevant factors that led to the unequal impact of the pandemic on BP between the two sexes.

The association of the higher chances of incidence of BP among the younger populations, as well as the greater chances of a worsening of pre-existing cases among older-aged individuals is also in line with previous findings¹³13 Dionne CE, Dunn KM, Croft PR. Does back pain prevalence really decrease with increasing age? A systematic review. Age Ageing 2006; 35(3):229-234.^,1717 Romero DE, Santana D, Borges P, Marques A, Castanheira D, Rodrigues JM, Sabbadini L. Prevalence, associated factors, and limitations related to chronic back problems in adults and elderly in Brazil. Cad Saude Publica 2018; 34(2):e00012817.. The average age found among those who developed BP (38 years) is near the average age for the development of CBP in Brazil from 2013 (35 years), according to findings from Romero et al.¹⁷17 Romero DE, Santana D, Borges P, Marques A, Castanheira D, Rodrigues JM, Sabbadini L. Prevalence, associated factors, and limitations related to chronic back problems in adults and elderly in Brazil. Cad Saude Publica 2018; 34(2):e00012817. The authors also pointed out that the prevention of BP should be intensified and carried out especially in younger-aged individuals¹⁷17 Romero DE, Santana D, Borges P, Marques A, Castanheira D, Rodrigues JM, Sabbadini L. Prevalence, associated factors, and limitations related to chronic back problems in adults and elderly in Brazil. Cad Saude Publica 2018; 34(2):e00012817.. Dionne et al.¹³13 Dionne CE, Dunn KM, Croft PR. Does back pain prevalence really decrease with increasing age? A systematic review. Age Ageing 2006; 35(3):229-234., in a systematic review, affirmed that the cognitive involvement, the increase in comorbidities, and the greater resilience to pain are possible hypotheses for the stability of the prevalence of BP in older populations. However, with advancing age, the severity of CBP is accentuated by the emergence of the limitations in one’s daily life activities (DLA) as of 50 years of age¹⁷17 Romero DE, Santana D, Borges P, Marques A, Castanheira D, Rodrigues JM, Sabbadini L. Prevalence, associated factors, and limitations related to chronic back problems in adults and elderly in Brazil. Cad Saude Publica 2018; 34(2):e00012817., considering that the degree of limitation is associated with the intensity of the pain³²32 Manchikanti L, Singh V, Datta S, Cohen SP, Hirsch JA, American Society of Interventional Pain Physicians. Comprehensive review of epidemiology, scope, and impact of spinal pain. Pain Physician 2009; 12(4):E35-E70..

According to data from the ConVid study, nearly 60% of the adult population reported a reduction in the level of physical exercise⁸8 Malta DC, Gomes CS, Barros MBA, Lima MG, Almeida WDS, Sá ACMGN, Prates EJS, Machado ÍE, Silva DRPD, Werneck AO, Damacena GN, Souza Júnior PRB, Azevedo LO, Montilla DER, Szwarcwald CL. Noncommunicable diseases and changes in lifestyles during the COVID-19 pandemic in Brazil. Rev Bras Epidemiol 2021; 24:e210009.. It is well-known that the regular practice of physical exercise is a key factor for the prevention of BP³³33 Steffens D, Maher CG, Pereira LSM, Stevens ML, Oliveira VC, Chapple M, Teixeira-Salmela LF, Hancock MJ. Prevention of low back pain: a systematic review and meta-analysis. JAMA Intern Med 2016; 176(2):199-208.. In this sense, the association between the reduction in the level of physical exercise and the greater incidence of BP, reported herein, was expected. It is important to highlight that, although doing physical exercise can be considered an individual behavior, this condition is prone to public health interventions, such as incentive policies and programs. Primary Health Care (PHC), through health advice strategies³⁴34 Lopes ACS, Toledo MTT, Câmara AMCS, Menzel HJK, Santos LC. Condições de saúde e aconselhamento sobre alimentação e atividade física na Atenção Primária à Saúde de Belo Horizonte-MG. Epidemiol Serv Saude 2014; 23(3):475-486. and the assisted practice of physical exercise³⁵35 Guarda F, Silva R, Silva S, Santana P. A atividade física como ferramenta de apoio às ações da Atenção Primária à Saúde. Rev Bras Ativ Fis Saude 2014; 19(2):265., has been responsible for the promotion of a more active lifestyle within the population. Such strategies have the potential to be used, even if at online (via telemedicine), to minimize the harmful effects of the pandemic on the incidence of the medical condition of BP. Nevertheless, the known underuse of the PHC in Brazil to combat the pandemic³⁶36 Ferigato S, Fernandez M, Amorim M, Ambrogi I, Fernandes LMM, Pacheco R. The Brazilian Government's mistakes in responding to the COVID-19 pandemic. Lancet 2020; 396(10263):1636., coupled with setbacks and impairments stemming from the new National Basic Health Policy³⁷37 Morosini MVGC, Fonseca AF, Lima LD, Morosini MVGC, Fonseca AF, Lima LD. Política Nacional de Atenção Básica 2017: retrocessos e riscos para o Sistema Único de Saúde. Saude Debate 2018; 42(116):11-24., have undermined the ability of SUS to effectively implement these strategies.

The association between the poor self-perception of one’s state of health and the occurrence of CBP was also shown in a previous study¹⁷17 Romero DE, Santana D, Borges P, Marques A, Castanheira D, Rodrigues JM, Sabbadini L. Prevalence, associated factors, and limitations related to chronic back problems in adults and elderly in Brazil. Cad Saude Publica 2018; 34(2):e00012817.. In the present study, the variable proved to be associated with a worsening of CBP, but not to the appearance of BP. This result is likely associated with the time in which the individual lived with the problem, given that the presence of chronic morbidities can lead to significant losses in one’s quality of life, which in turn leads to a poor self-perception of health³⁸38 Pavão ALB, Werneck GL, Campos MR. Autoavaliação do estado de saúde e a associação com fatores sociodemográficos, hábitos de vida e morbidade na população: um inquérito nacional. Cad Saude Publica 2013; 29(4):723-734..

The increase in housework during the first wave of the pandemic was associated with a higher prevalence of a worsening in the medical condition and the emergence of BP. Housework is a well-known risk factor for BP³⁹39 Garcia JB, Hernandez-Castro JJ, Nunez RG, Pazos MA, Aguirre JO, Jreige A, Delgado W, Serpentegui M, Berenguel M, Cantemir C. Prevalence of low back pain in Latin America: a systematic literature review. Pain Physician 2014; 17(5):379-391.^,4040 Osinuga A, Hicks C, Ibitoye SE, Schweizer M, Fethke NB, Baker KK. A meta-analysis of the association between physical demands of domestic labor and back pain among women. BMC Women's Health 2021; 21(1):150.. Cleaning, cooking, washing and ironing clothes, and taking care of the children can demand a lot, or even more, physically than some formal types of work⁴⁰40 Osinuga A, Hicks C, Ibitoye SE, Schweizer M, Fethke NB, Baker KK. A meta-analysis of the association between physical demands of domestic labor and back pain among women. BMC Women's Health 2021; 21(1):150.. The association with BP results from fatigue, produced through the long shifts that housework tends to demand, of work in inadequate postures, and of the action of repetitive movements⁴¹41 Habib RR, El Zein K, Hojeij S. Hard work at home: musculoskeletal pain among female homemakers. Ergonomics 2012; 55(2):201-211.. Work that studies the impacts of the pandemic on housework have reported that the workload increased for the population in general, but with a greater burden among women⁴²42 Deshpande A. The COVID-19 pandemic and lockdown: first effects on gender gaps in employment and domestic work in India. Working Papers 2020; 30.^,4343 Moreno MJG, Piqueras CC. Pandemia sanitaria y doméstica. El reparto de las tareas del hogar en tiempos del Covid-19. Rev Ciencias Sociales 2020; 26(4):28-34., reinforcing the hypothesis that this can be a factor associated with worse conditions related to BP during the period.

In this study, the feeling of sadness or depression has also proven to be associated with BP, especially with the worsening of CBP. Nevertheless, the causal relationship is not necessarily one-way. According to what Hurwitz et al.¹⁶16 Hurwitz EL, Morgenstern H, Yu F. Cross-sectional and longitudinal associations of low-back pain and related disability with psychological distress among patients enrolled in the UCLA Low-Back Pain Study. J Clin Epidemiol 2003; 56(5):463-471. propose, the psychological suffering is not only a possible cause, but also the consequence of BP, that is, it presents a relationship of interdependence. In this sense, it is possible to hypothesize that the high incidence, prevalence, and aggravation rates of the BP cases reported here, as well as the impact of the pandemic on one’s state of mind, stress, and mental state of the populations in Brazil⁴4 Barros MBA, Lima MG, Malta DC, Szwarcwald CL, Azevedo RCS, Romero D, Souza Júnior PRB, Azevedo LO, Machado IE, Damacena GN, Gomes CS, Werneck AO, Silva DRPD, Pina MF, Gracie R. Relato de tristeza/depressão, nervosismo/ansiedade e problemas de sono na população adulta brasileira durante a pandemia de COVID-19. Epidemiol Serv Saude 2020; 29(4):e2020427.^,55 Malta DC, Gomes CS, Szwarcwald CL, Barros MBA, Silva AG, Prates EJS, Machado IE, Souza Júnior PRB, Romero D, Damacena GN, Azevedo LO, Pina MF, Werneck AO, Silva DRP. Distanciamento social, sentimento de tristeza e estilos de vida da população brasileira durante a pandemia de COVID-19 [Internet]. 2020. [citado 2021 abr 13]. Disponível em: https://preprints.scielo.org/index.php/scielo/preprint/view/1371/version/1465
https://preprints.scielo.org/index.php/s... and in the world⁴⁴44 Brooks SK, Webster RK, Smith LE, Woodland L, Wessely S, Greenberg N, et al. The psychological impact of quarantine and how to reduce it: rapid review of the evidence. Lancet 2020; 395(10227):912-920.^,4545 Schmidt B, Crepaldi MA, Bolze SDA, Neiva-Silva L, Demenech LM. Saúde mental e intervenções psicológicas diante da pandemia do novo coronavírus (COVID-19). Estud Psicol 2020; 37:e200063., can mutually be one of the causes of the increase perceived in each of these conditions.

The changes related to the workplace due to the pandemic also showed an association with the incidence of BP. Those who began to work from home presented greater chances of developing BP. These findings corroborate with those of a study conducted in Turkey, which illustrated that people who began to work home office showed significantly higher rates of BP than did those who continued to work in their regular workplaces⁴⁶46 Celenay ST, Karaaslan Y, Mete O, Kaya DO. Coronaphobia, musculoskeletal pain, and sleep quality in stay-at home and continued-working persons during the 3-month COVID-19 pandemic lockdown in Turkey. Chronobiol Int 2020; 37(12):1778-1785.. Another study, which examined a wide range of manifestations of pain among individuals who began to work home office during the pandemic, reported that BP was the most common among all of the studied manifestations⁴⁷47 Pekyavas NÖ, Pekyavas E. Investigation of the pain and disability situation of the individuals working "home-office" at home at the COVID-19 isolation process. Int J Disabil Sports Health Sci 2020; 3(2):100-104.. Two hypotheses can be raised concerning the causes of these manifestations. The first of these concerns the prolonged time in which the individuals spend seated, which implies a lack of activation of the lower back muscle⁴⁸48 Mörl F, Bradl I. Lumbar posture and muscular activity while sitting during office work. J Electromyogr Kinesiol 2013; 23(2):362-368.. Another factor consists of the improvisation of home office spaces, without adequate chairs and office furniture, without proper pauses, and with a clear increase in the workload among those who work remotely⁴⁹49 Mendes DC, Filho HNH, Tellechea J. A realidade do trabalho home office na atipicidade pandêmica. Rev Valore 2020; 5:160-191.. This overload can affect the individual, both directly, through the even longer exposure to the seated position, as well as indirectly, through the mental overload, which in turn leads to higher levels of stress⁵⁰50 Guimarães BM, Martins LB, Azevedo LS, Andrade MA. Análise da carga de trabalho de analistas de sistemas e dos distúrbios osteomusculares. Fisioter Mov 2011; 24(1):115-124..

Another proven scenario is that those who did not work either before or after the beginning of the pandemic also presented higher chances of developing BP. This may be more difficult to justify, given that this population did not go through changes related to work due to the pandemic. Nonetheless, it can be inferred that this association may well be related to psychological factors and to their despair within the work market, worsened by the economic crisis and the consequent development of other diseases, such as depression, heavily associated with the prevalence of CBP¹⁷17 Romero DE, Santana D, Borges P, Marques A, Castanheira D, Rodrigues JM, Sabbadini L. Prevalence, associated factors, and limitations related to chronic back problems in adults and elderly in Brazil. Cad Saude Publica 2018; 34(2):e00012817..

In Brazil, a high prevalence of CBP was found (33.9%) at the beginning of the pandemic as compared to data from the 2019 NHS (23.4%)¹⁸18 Andrade FCD, Chen XS. A biopsychosocial examination of chronic back pain, limitations on usual activities, and treatment in Brazil, 2019. PLoS One 2022; 17(6):e0269627.. If this prevalence is added to the incidence during the period, one can reach a proportion of 61% of Brazilians with some type of BP during the pandemic. One should consider that the ConVid Study was applied between April and May 2020 and that the pandemic had been ongoing for more than two years. Thus, one can expect that a significant part of those who began to have back problems during the pandemic will most likely develop CBP as well.

If this scenario is confirmed, the country will become misaligned with the main guiding principles of the global strategy of “Decade of Healthy Aging, 2020-2030”, proposed by the World Health Organization (WHO), considering that the key concept to understand healthy aging is the functional skill, that is the capacity (physical and mental) of individuals to interact with the environment in which they live. This perspective will certainly be compromised by the disability promoted by the increase in the number of cases and by the worsening of CBP. In other words, the main cause of years lost due to disability, according to the Disease Burden study, will still be significant²⁴24 Hoy D, March L, Brooks P, Blyth F, Woolf A, Bain C, Williams G, Smith E, Vos T, Barendregt J, Murray C, Burstein R, Buchbinder R. The global burden of low back pain: estimates from the Global Burden of Disease 2010 study. Ann Rheum Dis 2014; 73(6):968-974.. There is also strong evidence that COVID-19 itself can present musculoskeletal symptoms, among which is BP⁵¹51 Abdullahi A, Candan SA, Abba MA, Bello AH, Alshehri MA, Victor EA, Umar NA, Kundakci B. Neurological and musculoskeletal features of COVID-19: a systematic review and meta-analysis. Front Neurol 2020; 11:687., which would cause twice as much harm (direct and indirect) in the condition studied within the pandemic scenario.

As this study was conducted on the internet, the populations with a lower level of education and without access to the internet may have been under-represented in the ConVid Study sample. Nonetheless, the large sample number and the subsequent weighting with the 2019 Continuous PNAD data minimize this limitation²⁸28 Szwarcwald C, Souza-Júnior P, Damacena G, Malta D, Barros M, Romero D, Almeida WDS, Azevedo LO, Machado ÍE, Lima MG, Werneck AO, Silva DRPD, Gomes CS, Ferreira APS, Gracie R, Pina MF. ConVid - Pesquisa de Comportamentos pela Internet durante a pandemia de COVID-19 no Brasil: concepção e metodologia de aplicação. Cad Saude Publica 2021; 37(3):e00268320.. Other limitations of this study refer to the questions used to measure the outcomes of this study. First, the question used to identify the presence of CBP does not define a minimum time to consider chronicity, which may have overestimated the prevalence²⁵25 David CN, Deligne LMC, Silva RS, Malta DC, Duncan BB, Passos VMA, Cousin E. The burden of low back pain in Brazil: estimates from the Global Burden of Disease 2017 Study. Popul Health Metrics 2020; 18(Suppl. 1):12., making it difficult to perform a comparative analysis with international studies¹⁹19 Meucci RD, Fassa AG, Faria NMX. Prevalence of chronic low back pain: systematic review. Rev Saude Publica 2015; 49:73.. By contrast, as it was described in this sense in the NHS, it was possible to compare the question with national studies¹⁵15 Malta DC, Oliveira MM, Andrade SSCA, Caiaffa WT, Souza MFM, Bernal RTI. Fatores associados à dor crônica na coluna em adultos no Brasil. Rev Saude Publica 2017; 51(Supl. 1):9s.^,1717 Romero DE, Santana D, Borges P, Marques A, Castanheira D, Rodrigues JM, Sabbadini L. Prevalence, associated factors, and limitations related to chronic back problems in adults and elderly in Brazil. Cad Saude Publica 2018; 34(2):e00012817.^,1818 Andrade FCD, Chen XS. A biopsychosocial examination of chronic back pain, limitations on usual activities, and treatment in Brazil, 2019. PLoS One 2022; 17(6):e0269627..

As regards the questions used to measure the incidence and worsening of BP, one other limitation is that the ConVid Study presumes that, with the pandemic, all of the participants had changes in their day-to-day activities, which can lead to more reports of BP among the participants. Finally, the question used to measure the incidence lists less definitions for BP than used to identify CBP, which may have generated an under-estimation of the incidence. Despite these limitations, the comparison made with data from the NHS²⁸28 Szwarcwald C, Souza-Júnior P, Damacena G, Malta D, Barros M, Romero D, Almeida WDS, Azevedo LO, Machado ÍE, Lima MG, Werneck AO, Silva DRPD, Gomes CS, Ferreira APS, Gracie R, Pina MF. ConVid - Pesquisa de Comportamentos pela Internet durante a pandemia de COVID-19 no Brasil: concepção e metodologia de aplicação. Cad Saude Publica 2021; 37(3):e00268320. demonstrates the robustness and relevance of the results, faced with the unavailability of other sources of up-to-date and nationwide information about BP.

Finally, the present study’s findings demonstrate that the first wave of the COVID-19 pandemic increased BP among Brazilian adults, especially among women, as well as among those who felt sad/depressed and those who had an increased burden in housework. Therefore, it is necessary to reinforce policies to promote physical and mental health in the scope of PHC and improve access to adequate treatment for BP.

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