Abstracts

Introduction

Humans are social beings, and a sense of belonging is an essential human need that compels us to build and to maintain long-lasting interpersonal bonds ¹1. Baumeister RF, Leary MR. The need to belong: desire for interpersonal attachments as a fundamental human motivation. Psychol Bull 1995; 117:497-529.. Interacting with others and with the environment is an evolutionary legacy essential to mental health. Social connection is associated with positive affect, self-esteem, and happiness, whereas social exclusion is associated with anxiety, loneliness, and depression ¹1. Baumeister RF, Leary MR. The need to belong: desire for interpersonal attachments as a fundamental human motivation. Psychol Bull 1995; 117:497-529.^,22. Carvallo M, Gabriel S. No man is an island: the need to belong and dismissing avoidant attachment style. Pers Soc Psychol Bull 2006; 32:697-709..

Loneliness is a distressing negative affect due to a discrepancy between one’s desired and achieved level of social connection, that could be either in quality or quantity ³3. Perlman D, Peplau LA. Toward a social psychology of loneliness. In: Duck S, Gilmour R, editors. Personal relationships in disorder. London: Academic Press; 1981. p. 31-56.. On the other hand, social isolation is one’s separation from individuals or groups from a lack of social contact, such as living alone and having few or no social bonds ⁴4. Holt-Lunstad J, Smith TB, Baker M, Harris T, Stephenson D. Loneliness and social isolation as risk factors for mortality: a meta-analytic review. Perspect Psychol Sci 2015; 10:227-37.. Since loneliness is a subjective perception, it could occur even without social isolation. Similarly, socially isolated individuals may not experience loneliness.

Growing evidence shows that more studies should analyze loneliness and social isolation in public health concerns. Both are associated with cardiovascular diseases ⁵5. Leigh-Hunt N, Bagguley D, Bash K, Turner V, Turnbull S, Valtorta N, et al. An overview of systematic reviews on the public health consequences of social isolation and loneliness. Public Health 2017; 152:157-71.^,66. Xia N, Li H. Loneliness, social isolation and cardiovascular health. Antioxid Redox Signal 2018; 28:837-51.^,77. Valtorta NK, Kanaan M, Gilbody S, Ronzi S, Hanratty B. Loneliness and social isolation as risk factors for coronary heart disease and stroke: systematic review and meta-analysis of longitudinal observational studies. Heart 2016; 102:1009-16. and are risk factors for early mortality, similarly to well established risk factors, including inactivity, obesity, and substance abuse ⁴4. Holt-Lunstad J, Smith TB, Baker M, Harris T, Stephenson D. Loneliness and social isolation as risk factors for mortality: a meta-analytic review. Perspect Psychol Sci 2015; 10:227-37.. Loneliness is also associated with depression ⁸8. Cacioppo JT, Hughes ME, Waite LJ, Hawkley LC, Thisted RA. Loneliness as a specific risk factor for depressive symptoms: cross-sectional and longitudinal analysis. Psychol Aging 2006; 21:140-51., cognitive impairment and dementia ⁹9. Wilson RS, Krueger KR, Arnold SE, Schneider JA, Kelly JF, Barnes LL, et al. Loneliness and risk of Alzheimer disease. Arch Gen Psychiatry 2007; 64:234-40.^,1010. Lara E, Martín-María N, De la Torre-Luque A, Koyanagi A, Vancampfort D, Izquierdo A, et al. Does loneliness contribute to mild cognitive impairment and dementia? A systematic review and meta-analysis of longitudinal studies. Ageing Res Rev 2019; 52:7-16.^,1111. Zhou Z, Wang P, Fang Y. Loneliness and the risk of dementia among older Chinese adults: gender differences. Aging Ment Health 2018; 22:519-25., diabetes, and migraine ¹²12. Christiansen J, Larsen FB, Lasgaard M. Do stress, health behavior, and sleep mediate the association between loneliness and adverse health conditions among older people? Soc Sci Med 2016; 152:80-6., resulting in a higher risk of death, hospitalization, and use of emergency services in patients with heart failure ¹³13. Manemann SM, Chamberlain AM, Roger VL, Griffin JM, Boyd CM, Cudjoe TKM, et al. Perceived social isolation and health outcomes in patients with heart failure. J Am Heart Assoc 2018; 7:e008069..

Whether loneliness affects health by health behavior or not is still uncertain ¹²12. Christiansen J, Larsen FB, Lasgaard M. Do stress, health behavior, and sleep mediate the association between loneliness and adverse health conditions among older people? Soc Sci Med 2016; 152:80-6.^,1414. Richard A, Rohrmann S, Vandeleur CL, Schmid M, Barth J, Eichholzer M. Loneliness is adversely associated with physical and mental health and lifestyle factors: results from a Swiss national survey. PLoS One 2017; 12:e0181442.^,1515. Kobayashi LC, Steptoe A. Social isolation, loneliness, and health behaviors at older ages: longitudinal cohort study. Ann Behav Med 2018; 52:582-93.^,1616. Luo Y, Hawkley LC, Waite LJ, Cacioppo JT. Loneliness, health, and mortality in old age: a national longitudinal study. Soc Sci Med 2012; 74:907-14.. Evidence shows that socially excluded individuals tend to have less control of impulsivity and are more likely to engage in harmful health behaviors and unreasonable decisions ¹⁷17. DeWall CN, Pond RS. Loneliness and smoking: the costs of the desire to reconnect. Self Identity 2011; 10:375-85.. Some studies have associated smoking with loneliness, but this association is still indefinite ¹⁸18. Shankar A, McMunn A, Banks J, Steptoe A. Loneliness, social isolation, and behavioral and biological health indicators in older adults. Health Psychol 2011; 30:377-85.^,1919. Stickley A, Koyanagi A, Roberts B, Richardson E, Abbott P, Tumanov S, et al. Loneliness: its correlates and association with health behaviours and outcomes in nine countries of the Former Soviet Union. PLoS One 2013; 8:e67978..

Smoking is the major preventable cause of death worldwide, greatly affecting public health. Tobacco use is one of the most important risk factors associated with deaths from noncommunicable diseases, including cardiovascular diseases, cancer, chronic lung diseases, and diabetes, which cause more than two thirds of deaths in developing countries ²⁰20. World Health Organization. Report on the global tobacco epidemic, 2019. Geneva: World Health Organization; 2019.. According to data from the Risk and Protective Factors Surveillance System for Chronic Non-Comunicable Diseases Through Telephone Interview survey (Vigitel, 2018) ²¹21. Ministério da Saúde. Vigitel Brasil 2018: vigilância de fatores de risco e proteção para doenças crônicas por inquérito telefônico: estimativas sobre frequência e distribuição sociodemográfica de fatores de risco e proteção para doenças crônicas nas capitais dos 26 estados brasileiros e no Distrito Federal em 2018. Brasília: Ministério da Saúde; 2019. on the 27 capitals of the Brazilian Federative Units, 9.3% of Brazilian adults smoke, mainly men (12.1%) than women (6.9%). Prevalence was higher for 55 and 64 years old adults (12.3%) than for those aged 65 years and older (6.1%). The prevalence of tobacco use possibly declines with age because of early mortality in smokers and smoking cessation from the onset of chronic diseases ²²22. Zaitune MPA, Barros MBA, Lima MG, César CLG, Carandina L, Goldbaum M, et al. Fatores associados ao tabagismo em idosos: Inquérito de Saúde no Estado de São Paulo (ISA-SP). Cad Saúde Pública 2012; 28:583-96..

Older adults are especially susceptible to developing tobacco-related diseases since they were more exposed to tobacco and unfiltered cigarettes during their lives. Furthermore, smoking tends to affect the health conditions of individuals in this age group, increasing mortality and healthcare costs ²²22. Zaitune MPA, Barros MBA, Lima MG, César CLG, Carandina L, Goldbaum M, et al. Fatores associados ao tabagismo em idosos: Inquérito de Saúde no Estado de São Paulo (ISA-SP). Cad Saúde Pública 2012; 28:583-96..

Factors associated with tobacco use in this age group must therefore be assessed to improve interventions to combat it. Considering that older adults are under a higher risk of social isolation ¹⁵15. Kobayashi LC, Steptoe A. Social isolation, loneliness, and health behaviors at older ages: longitudinal cohort study. Ann Behav Med 2018; 52:582-93. and its effects, this study aims to investigate the association of social support, companionship, and loneliness with smoking and smoking cessation in older adults from Campinas, São Paulo State, Brazil, stratified by emotional problems and common mental disorders (CMDs), considering the strong association between loneliness and emotional problems ¹⁴14. Richard A, Rohrmann S, Vandeleur CL, Schmid M, Barth J, Eichholzer M. Loneliness is adversely associated with physical and mental health and lifestyle factors: results from a Swiss national survey. PLoS One 2017; 12:e0181442..

Materials and methods

This is a cross-sectional, population-based study with 986 non-institutionalized individuals aged 60 years or older, living in the urban areas of the municipality of Campinas. Data were collected from the Health Survey of the Municipality of Campinas (ISACamp 2014/2015).

The sample was obtained by cluster sampling in two stages. In the first stage, 70 census sectors of Campinas were drawn, with a probability proportional to the number of households, by selecting 14 census sectors from each of the five health districts of the city. In the second stage, households were selected using systematic drawing.

The sample size was defined considering the maximal variability for the frequency of the studied events (p = 0.50), a 95% confidence interval (95%CI), 5% sampling error, and design effect equal to 2. Therefore, a sample of 1,000 individuals was defined for the age group 10-19 years old, 1,000 for people aged 60 years or older, and 1,400 for adults 20 to 59 years old.

The mean number of residents in each household was calculated based on the 2010 Brazilian census (person/household ratio). The number of residences to be visited was thus defined by dividing the established sample size for each age group by the person/household ratio, resulting in 2,898 residences for adolescents, 950 for adults, and 3,326 for older adults, already considering the non-response rates of 27%, 22%, and 20%, respectively, based on a previous survey. All residents of the selected age group for each household were interviewed ²³23. Alves MCGP, Escuder MML, Claro RM, da Silva NN. Sorteio intradomiciliar em inquéritos de saúde. Rev Saúde Pública 2014; 48:86-93.. This study only analyzed data from individuals aged 60 years or older.

The survey was conducted using a structured questionnaire divided into 11 thematic blocks, applied by trained and supervised interviewers with tablet computers.

The dependent variables studied were:

The analysis was performed using the statistical software Stata 15.0 (https://www.stata.com), which considers the necessary weights of the sampling design. Smoking prevalence was estimated according to the independent variables and the associations were tested using the chi-square test, considering 5% a significance level. The prevalence ratios (PR) adjusted for age group and income and the 95%CI were calculated using Poisson regression models, with robust variance. The association of smoking with Internet use was also adjusted for income. The PR and 95%CI of the association between smoking and loneliness were estimated in the stratified analysis by emotional problems and CMDs. A multiplicative interaction term adjusted for sex, age, loneliness, and emotional problems was included in the models to understand the possible effects of emotional problems in the association between smoking and loneliness. The ISACamp 2014/2015 project was approved by the Research Ethics Committee of the School of Medical Sciences/State University of Campinas (process n. 409.714 of September 30, 2013; CAAE 20547513.2.0000.5404).

Results

In total, 986 individuals with a mean age of 70.0 years old (95%CI: 69.3-70.8) were analyzed. Older adults had a smoking prevalence of 10.4% (95%CI: 8.5-12.7), loneliness prevalence of 13.9% (95%CI: 11.7-16.3), and smoking cessation prevalence of 69.9% (95%CI: 65.1-74.2). Women had a higher prevalence of loneliness (16.6%; 95%CI: 13.0-19.6) than men (10.2%; 95%CI: 7.4-14.0) (data not shown).

Table 1 shows the associations of social support, companionship, and emotional problems with loneliness in older adults. Loneliness was associated with living alone (PR = 2.33; 95%CI: 1.51-3.62), not living with a partner (PR = 2.11; 95%CI: 1.30-3.43), and not having someone to turn to if needed (PR = 5.34; 95%CI: 3.89-7.34). Loneliness was more than twice as prevalent in those who reported emotional problems and almost four times more frequent in those with CMDs (PR = 2.31; 95%CI: 1.59-3.56 and PR = 3.77; 95%CI: 2.72-5.22, respectively). Not using the Internet was also associated with loneliness (PR = 2.19; 95%CI: 1.17-4.09).

In the analysis adjusted for sex and age, among the social support variables, only marital status was associated with smoking (PR = 1.51; 95%CI: 1.03-2.22). Individuals who were often or always lonely had a higher prevalence of smoking than those who were never or rarely lonely (PR = 2.25; 95%CI: 1.38-3.66). Not living with a partner was associated with a lower prevalence of smoking cessation, on the limit of statistical significance (PR = 0.86; 95%CI: 0.73-1.00) (Table 2).

Table 3 shows the analysis of the association between smoking and loneliness stratified by the presence of CMDs and self-reported emotional problems. We found no statistical association between loneliness and smoking in older adults who reported no emotional problems or CMDs. On the other hand, smoking prevalence was three times higher in lonely individuals with emotional problems than in those who were not lonely, but also had emotional problems (PR = 3.78; 95%CI: 1.93-7.38) and more than five times higher in those with CMDs (PR = 5.42; 95%CI: 1.89-15.5). We found a significant interaction between the presence of CMDs or self-reported emotional problems and loneliness in the association with smoking (CMDs or emotional problems report vs. loneliness = 6.24; 95%CI: 1.37-28.47).

Table 4 shows the analysis of the association between smoking cessation and loneliness, stratified by the presence of CMDs and self-reported emotional problems. Smoking cessation had no significant association with loneliness in older adults with no emotional problems or CMDs. On the other hand, smoking cessation was 31% lower for those with emotional problems (PR = 0.69; 95%CI: 0.48-1.00) and 56% lower for those with CMDs (PR = 0.44; 95%CI: 0.20-0.96). We found a significant interaction between the presence of CMDs or self-reported emotional problems and loneliness in the association with smoking cessation.

Discussion

We found a loneliness prevalence of 13.9% in the older population of Campinas. Among older adults, 10.4% currently smoke and among individuals who smoked at some point, 69.9% quit smoking. Social support variables were not associated with smoking or smoking cessation in this age group, except for marital status. Smoking was not independently associated with emotional problems and CMDs, but was strongly associated with often or always feeling lonely. In the stratified analysis, loneliness was associated with smoking only for self-reported emotional problems or CMDs. We also found that lonely individuals who had emotional problems or CMDs had a lower prevalence of smoking cessation. These findings indicate that emotional problems have a moderator role in the association of loneliness with smoking and smoking cessation.

Smoking prevalence among the older adults of Campinas (10.4%) corresponds to 14,672 smokers, in absolute numbers. This percentage can be compared to the prevalence found by Vigitel 2018 ²¹21. Ministério da Saúde. Vigitel Brasil 2018: vigilância de fatores de risco e proteção para doenças crônicas por inquérito telefônico: estimativas sobre frequência e distribuição sociodemográfica de fatores de risco e proteção para doenças crônicas nas capitais dos 26 estados brasileiros e no Distrito Federal em 2018. Brasília: Ministério da Saúde; 2019. for the group of the 27 Brazilian capitals (12.3% between 55 and 64 years old and 6.1% for 65 years and older) and to a meta-analysis that estimated a 13% global prevalence of smoking in older adults in 2010 ²⁵25. Marinho V, Laks J, Coutinho ESF, Blay SL. Tobacco use among the elderly: a systematic review and meta-analysis. Cad Saúde Pública 2010; 26:2213-33.. In 2002, smoking prevalence was 12.2% for older adults in regions of the state of São Paulo ²²22. Zaitune MPA, Barros MBA, Lima MG, César CLG, Carandina L, Goldbaum M, et al. Fatores associados ao tabagismo em idosos: Inquérito de Saúde no Estado de São Paulo (ISA-SP). Cad Saúde Pública 2012; 28:583-96.. Results possibly differ because of the age group and period studied, considering that the prevalence of tobacco use has decreased in Brazil over the last decade ²¹21. Ministério da Saúde. Vigitel Brasil 2018: vigilância de fatores de risco e proteção para doenças crônicas por inquérito telefônico: estimativas sobre frequência e distribuição sociodemográfica de fatores de risco e proteção para doenças crônicas nas capitais dos 26 estados brasileiros e no Distrito Federal em 2018. Brasília: Ministério da Saúde; 2019..

In São Paulo, smoking prevalence was high even among those who had chronic diseases, including 8.7% of smokers among those with high blood pressure, 20.9% among those with previous history of stroke, 16.2% among those who reported emotional problems, and 17.8% among those with chronic lung diseases ²²22. Zaitune MPA, Barros MBA, Lima MG, César CLG, Carandina L, Goldbaum M, et al. Fatores associados ao tabagismo em idosos: Inquérito de Saúde no Estado de São Paulo (ISA-SP). Cad Saúde Pública 2012; 28:583-96.. These findings emphasize that public policies are essential to encourage smoking cessation in older adults.

Although emotional problems and CMDs were strongly associated with loneliness but not with smoking, they modified the association between loneliness and tobacco use. Loneliness and self-reported emotional problems or CMDs had a synergistic effect in the association with smoking. Martínez-Vispo et al. ²⁶26. Martínez-Vispo C, López-Durán A, Rodríguez-Cano R, del Río EF, Senra C, Becoña E. Effect of depressive symptoms and sex on the relationship between loneliness and cigarette dependence: a moderated mediation. J Psychol 2019; 153:701-13. also found a moderator role of depressive symptoms in the relation between loneliness and smoking. Several studies have established an association between loneliness and depressive symptoms ¹⁴14. Richard A, Rohrmann S, Vandeleur CL, Schmid M, Barth J, Eichholzer M. Loneliness is adversely associated with physical and mental health and lifestyle factors: results from a Swiss national survey. PLoS One 2017; 12:e0181442.^,1616. Luo Y, Hawkley LC, Waite LJ, Cacioppo JT. Loneliness, health, and mortality in old age: a national longitudinal study. Soc Sci Med 2012; 74:907-14.^,2727. Cacioppo JT, Hawkley LC, Thisted RA. Perceived social isolation makes me sad: five year cross-lagged analysis of loneliness and depressive symptomatology in the Chicago Health, Aging, and Social Relations study. Psychol Aging 2010; 25:453-63.^,2828. Hagerty BM, Williams AR. The effect of sense of belonging, social support, conflict, and loneliness on depression. Nurs Res 1999; 48:215-9.. On the other hand, evidence on the association of emotional problems and CMDs with smoking is still divergent ²⁹29. Burns A, Strawbridge JD, Clancy L, Doyle F. Exploring smoking, mental health and smoking-related disease in a nationally representative sample of older adults in Ireland: a retrospective secondary analysis. J Psychosom Res 2017; 98:78-86.^,3030. Borim FSA, Barros MBA, Botega NJ. Transtorno mental comum na população idosa: pesquisa de base populacional no Município de Campinas, São Paulo, Brasil. Cad Saúde Pública 2013; 29:1415-26..

In this study, smoking was not associated with most social isolation variables, but was significantly associated with loneliness. In a meta-analysis, Dyal & Valente ³¹31. Dyal SR, Valente TW. A systematic review of loneliness and smoking: small effects, big implications. Subst Use Misuse 2015; 50:1697-716. reported an association between loneliness and tobacco use in half of the analyzed studies. On the other hand, in a longitudinal study with adults aged 52 years and older, Kobayashi & Steptoe ¹⁵15. Kobayashi LC, Steptoe A. Social isolation, loneliness, and health behaviors at older ages: longitudinal cohort study. Ann Behav Med 2018; 52:582-93. found an association between social isolation and smoking, but not between loneliness and smoking. Choi & DiNitto ³²32. Choi NG, DiNitto DM. Role of new diagnosis, social isolation, and depression in older adults' smoking cessation. Gerontologist 2015; 55:793-801. also observed an association between social isolation and tobacco use.

Tobacco addiction is a multifactorial phenomenon which cannot be explained exclusively by the effects of nicotine, considered a weak reinforcer ³³33. Fagerström K. Determinants of tobacco use and renaming the FTND to the Fagerstrom Test for Cigarette Dependence. Nicotine Tob Res 2012; 14:75-8.. Besides the pharmacological role of the chemical elements on the cigarettes and the positive reinforcement of the smoking “ritual”, psychosocial aspects are also crucial in the development of dependence. Smoking could be means of socializing with unknown people or group affiliations, especially for young individuals. Cigarettes could even become a “friend” in situations of loneliness and briefly reduce anxiety ³³33. Fagerström K. Determinants of tobacco use and renaming the FTND to the Fagerstrom Test for Cigarette Dependence. Nicotine Tob Res 2012; 14:75-8.^,3434. Borges MTT, Simões-Barbosa RH. Cigarro "companheiro": o tabagismo feminino em uma abordagem crítica de gênero. Cad Saúde Pública 2008; 24:2834-42.. On the other hand, smoking is bidirectionally related with depressive symptoms and has a causal relationship with depression, possibly because of nicotine receptors in the brain, causing a dysfunction in neurotransmitters such as dopamine and serotonin ³⁵35. Wootton RE, Richmond RC, Stuijfzand BG, Lawn RB, Sallis HM, Taylor GM, et al. Evidence for causal effects of lifetime smoking on risk for depression and schizophrenia: a Mendelian randomisation study. Psychol Med 2019; 50:2435-43..

In our study, loneliness was not independently associated with smoking cessation. Not living with a partner was associated with a less prevalent smoking cessation, on the limit of statistical significance. In the stratified analysis, lonely individuals with mental health problems had a lower prevalence of smoking cessation. Other studies have reported loneliness as a negative predictor of successful smoking cessation, associated with a lower self-efficacy in quitting smoking ¹⁵15. Kobayashi LC, Steptoe A. Social isolation, loneliness, and health behaviors at older ages: longitudinal cohort study. Ann Behav Med 2018; 52:582-93.^,3636. Shuter J, Moadel AB, Kim RS, Weinberger AH, Stanton CA. Self-efficacy to quit in HIV-infected smokers. Nicotine Tob Res 2014; 16:1527-31.. Smoking cessation has potential benefits in morbimortality and quality of life for older adults, including decreased risk of cardiac deaths and mortality from tobacco-related cancer and chronic obstructive pulmonary disease (COPD), decreased risk of coronary events, reduced rate of lung function decline, enhanced tolerance to physical activity, and improved respiratory symptoms ³⁷37. Müezzinler A, Mons U, Gellert C, Schöttker B, Jansen E, Kee F, et al. Smoking and all-cause mortality in older adults: results from the CHANCES Consortium. Am J Prev Med 2015; 49:e53-63.^,3838. LaCroix AZ, Omenn GS. Older adults and smoking. Clin Geriatr Med 1992; 8:69-87.. Nevertheless, smoking cessation is still challenging, which is why understanding the dependence process is essential to develop strategies for successful interventions seeking abstinence.

According to data from the Brazilian National Cancer Institute (INCA) & Oswaldo Cruz Foundation (Fiocruz) ³⁹39. Instituto Nacional de Câncer José Alencar Gomes da Silva; Fundação Oswaldo Cruz. O controle do tabaco no Brasil: uma trajetória. http://bvsms.saude.gov.br/bvs/publicacoes/exposicao_controle_tabaco_brasil_trajetoria.pdf (accessed on 07/Jan/2021).
http://bvsms.saude.gov.br/bvs/publicacoe... and from Vigitel 2018 ²¹21. Ministério da Saúde. Vigitel Brasil 2018: vigilância de fatores de risco e proteção para doenças crônicas por inquérito telefônico: estimativas sobre frequência e distribuição sociodemográfica de fatores de risco e proteção para doenças crônicas nas capitais dos 26 estados brasileiros e no Distrito Federal em 2018. Brasília: Ministério da Saúde; 2019., smoking prevalence in the adult population decreased favorably over the years, from 34.5% in 1989, when the National Program for Tobacco Control coordinated by INCA was created, to 15.7% in 2006, and gradually declining until reaching 9.3% in 2018. For people aged between 55 and 64 years, the frequency remained substantial, decreasing from 15.4% in 2006 to 12.3% in 2018.

The decline in the smoking prevalence in Brazil comes from the governmental efforts in the last decades for tobacco control, which include the ban on smoking in closed places destined for collective use, prohibition of sale for people aged under 18 years, advertising banners, packages regulation, exposure of warnings in the packages and in means of communication and, more recently, the implementation of smoking cessation treatment in the public healthcare system. Most smokers started using tobacco during childhood and adolescence. As a result, older adults have been more exposed to tobacco over the years, reinforcing the dependence process ³⁹39. Instituto Nacional de Câncer José Alencar Gomes da Silva; Fundação Oswaldo Cruz. O controle do tabaco no Brasil: uma trajetória. http://bvsms.saude.gov.br/bvs/publicacoes/exposicao_controle_tabaco_brasil_trajetoria.pdf (accessed on 07/Jan/2021).
http://bvsms.saude.gov.br/bvs/publicacoe... . Besides, over the last decades, smoking has changed from a symbol of health and social status to a sign of addiction and disease, with a sharp decline in its social acceptance. This transformation in the social image of smoking and the ban on smoking in closed public places could isolate older adults who smoke.

Because of the cross-sectional design of this and most studies regarding the analyzed association, we could not determine a causal relationship between loneliness and smoking, which would be likely bidirectional. A recent Mendelian randomization study found weak evidence that loneliness encouraged starting tobacco use and a high load of tobacco smoking or hindered cessation, and strong evidence that tobacco use increased the risk of loneliness ⁴⁰40. Wootton RE, Greenstone HSR, Abdellaoui A, Denys D, Verweij KJH, Munafò MR, et al. Bidirectional effects between loneliness, smoking and alcohol use: evidence from a Mendelian randomization study. Addiction 2021; 116:400-6.. Loneliness can lead to smoking from the need to belong, in some situations, or because of the resulting temporary relief of depressive symptoms. According to this and other studies, loneliness also seems to inhibit smoking cessation ¹⁵15. Kobayashi LC, Steptoe A. Social isolation, loneliness, and health behaviors at older ages: longitudinal cohort study. Ann Behav Med 2018; 52:582-93.^,3636. Shuter J, Moadel AB, Kim RS, Weinberger AH, Stanton CA. Self-efficacy to quit in HIV-infected smokers. Nicotine Tob Res 2014; 16:1527-31.. In turn, smoking and its associated social problems could lead to loneliness. Recent evidence showed a genetic association between loneliness and depressive symptoms. Therefore, since smoking increases depression risk, it could also increase chances of loneliness ³⁵35. Wootton RE, Richmond RC, Stuijfzand BG, Lawn RB, Sallis HM, Taylor GM, et al. Evidence for causal effects of lifetime smoking on risk for depression and schizophrenia: a Mendelian randomisation study. Psychol Med 2019; 50:2435-43.^,4141. Abdellaoui A, Sanchez-Roige S, Sealock J, Treur JL, Dennis J, Fontanillas P, et al. Phenome-wide investigation of health outcomes associated with genetic predisposition to loneliness. Hum Mol Genet 2019; 28:3853-65.. Subsequent studies must better explore these causal effects.

This study has limitations. The cross-sectional design could not establish a causal relationship between the variables. Our study is also subject to survival bias, considering that older adults who had been exposed to a higher load of tobacco use were also at a higher risk of early death, which can underestimate the magnitude of the findings.

Nevertheless, our research has the strength of being a population-based study, with a representative sample of an older urban population. Furthermore, to our knowledge, no other population-based Brazilian studies have reported on loneliness in older adults and few have analyzed the role of emotional problems in the association between smoking and loneliness.

Our study reinforces the association between loneliness and smoking in older adults with mental health disorders and emphasizes that these factors can likely impair smoking cessation. These findings allow better understanding the psychosocial aspects associated with cigarette dependence and smoking cessation in older adults, which helps develop strategies for successful interventions seeking improved social connection and mental health approaches.

Acknowledgments

The authors are grateful for the São Paulo State Research Foundation (FAPESP) for funding the fieldwork for ISACamp 2014/2015 and this research; and for the Health Department of the Municipality of Campinas and the Department of Health Surveillance of the Brazilian Ministry of Health for funding the execution of the survey. The Brazilian National Research Council (CNPq) granted the productivity scholarship to M. B. A. Barros (grant n. 309073/2015-4).

References

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