Abstracts

Introduction

Aging is associated with an increased prevalence of chronic noncommunicable diseases ¹1. Alharbi B, Masud N, Alajlan F, Alkhanein N, Alzahrani F, Almajed Z, et al. Association of elderly age and chronic illnesses: role of gender as a risk factor. J Family Med Prim Care 2020; 9:1684.^,22. Vetrano DL, Calderón-Larrañaga A, Marengoni A, Onder G, Bauer JM, Cesari M, et al. An international perspective on chronic multimorbidity: approaching the elephant in the room. J Gerontol A Biol Sci Med Sci 2018; 73:1350-6. and reduced physical functioning ³3. Forman-Hoffman VL, Ault KL, Anderson WL, Weiner JM, Stevens A, Campbell VA, et al. Disability status, mortality, and leading causes of death in the United States community population. Med Care 2015; 53:346-54.^,44. Millán-Calenti JC, Tubío J, Pita-Fernández S, González-Abraldes I, Lorenzo T, Fernández-Arruty T, et al. Prevalence of functional disability in activities of daily living (ADL), instrumental activities of daily living (IADL) and associated factors, as predictors of morbidity and mortality. Arch Gerontol Geriatr 2010; 50:306-10., which lead to a decreased well-being ⁵5. Lima MG, Barros MBA, Alves MCGP. Sentimento de felicidade em idosos: uma abordagem epidemiológica, ISA-Camp 2008. Cad Saúde Pública 2012; 28:2280-92. and quality of life ⁶6. Lima MG, Barros MBA, César CLG, Goldbaum M, Carandina L, Ciconelli RM. Impact of chronic disease on quality of life among the elderly in the state of Sao Paulo, Brazil: a population-based study. Rev Panam Salud Pública 2009; 25:314-21., as well as a greater risk of premature death ⁷7. Camargos MCS, Gonzaga MR, Costa JV, Bomfim WC. Disability-free life expectancy estimates for Brazil and major regions, 1998 and 2013. Ciênc Saúde Colet 2019; 24:737-48.^,88. Partridge L, Deelen J, Slagboom PE. Facing up to the global challenges of ageing. Nature 2018; 561:45-56..

Functional disability is an acquired difficulty in performing basic activities of daily living (ADLs) or more complex tasks that are fundamental to an independent life ⁹9. Alves LC, Leite IC, Machado CJ. The concept and measurement of functional disability in the elderly population: a literature review. Ciênc Saúde Colet 2008; 13:1199-207.. The prevalence and incidence of functional disabilities in Brazil has been the object of research over time ¹⁰10. Lebrão ML, Laurenti R. Health, well-being and aging: the SABE Study in São Paulo, Brazil. Rev Bras Epidemiol 2005; 8:127-68.^,1111. Nogueira SL, Ribeiro RCL, Rosado LEFPL, Franceschini SCC, Ribeiro AQ, Pereira ET. Fatores determinantes da capacidade funcional em idosos longevos. Revista Brasileira de Fisioterapia 2010; 14:322-9.^,1212. Nunes JD, Saes MO, Nunes BP, Siqueira FCV, Soares DC, Fassa MEG, et al. Indicadores de incapacidade funcional e fatores associados em idosos: estudo de base populacional em Bagé, Rio Grande do Sul. Epidemiol Serv Saúde 2017; 26:295-304.^,1313. Rodrigues MAP, Facchini LA, Thumé E, Maia F. Gender and incidence of functional disability in the elderly: a systematic review. Cad Saúde Pública 2009; 25 Suppl 3:S464-76..

Data from the 2013 and 2019 Brazilian National Health Survey (PNS, acronym in Portuguese) provide comprehensive and representative information on the prevalence of functional disabilities in Brazil. In the 2013 PNS, the total prevalence of disabilities regarding ADLs among people aged 60 years or older was 15.8% ¹⁴14. Schmidt TP, Wagner KJP, Schneider IJC, Danielewicz AL. Padrões de multimorbidade e incapacidade funcional em idosos brasileiros: estudo transversal com dados da Pesquisa Nacional de Saúde. Cad Saúde Pública 2020; 36:e00241619.^,1515. Santos DF, Barreto IDC, Silva RJS, Scher LML. Prevalência de incapacidade funcional e fatores associados em idosos brasileiros. Res Soc Dev 2022; 11:e27311528310.. The 2019 PNS reported a similar prevalence, highlighting the persistence of functional disabilities in the aging population ¹⁶16. PNS 2019: país tem 17,3 milhões de pessoas com algum tipo de deficiência. Agência IBGE Notícias 2021; 26 aug. https://agenciadenoticias.ibge.gov.br/agencia-sala-de-imprensa/2013-agencia-de-noticias/releases/31445-pns-2019-pais-tem-17-3-milhoes-de-pessoas-com-algum-tipo-de-deficiencia.
https://agenciadenoticias.ibge.gov.br/ag... ^,1717. Instituto Brasileiro de Geografia e Estatística. Pesquisa Nacional de Saúde 2019: ciclos de vida. https://biblioteca.ibge.gov.br/visualizacao/livros/liv101846.pdf (accessed on 16/Feb/2025).
https://biblioteca.ibge.gov.br/visualiza... . National and international studies report rates ranging from 12.0% to 36.1% ¹⁸18. Francisco PMSB, Assumpção D, Borim FSA, Yassuda MS, Neri AL. Risk of all-cause mortality and its association with health status in a cohort of community-dwelling older people: FIBRA study. Ciênc Saúde Colet 2021; 26:6153-64.^,1919. Farías-Antúnez S, Lima NP, Bierhals IO, Gomes AP, Vieira LS, Tomasi E. Incapacidade funcional para atividades básicas e instrumentais da vida diária: um estudo de base populacional com idosos de Pelotas, Rio Grande do Sul, 2014. Epidemiol Serv Saúde 2018; 27:e2017290.^,2020. Reyes-Ortiz CA, Ostir GV, Pelaez M, Ottenbacher KJ. Cross-national comparison of disability in Latin American and Caribbean persons aged 75 and older. Arch Gerontol Geriatr 2006; 42:21-33.^,2121. Giacomin KC, Peixoto SV, Uchoa E, Lima-Costa MF. Estudo de base populacional dos fatores associados à incapacidade funcional entre idosos na Região Metropolitana de Belo Horizonte, Minas Gerais, Brasil. Cad Saúde Pública 2008; 74:1260-70.. Recent Brazilian studies have expanded the understanding of functional disabilities among older adults ²²22. Alexandre TS, Corona LP, Nunes DP, Santos JLF, Duarte YAO, Lebrão ML. Disability in instrumental activities of daily living among older adults: gender differences. Rev Saúde Pública 2014; 48:379-89.. Alexandre et al. ²²22. Alexandre TS, Corona LP, Nunes DP, Santos JLF, Duarte YAO, Lebrão ML. Disability in instrumental activities of daily living among older adults: gender differences. Rev Saúde Pública 2014; 48:379-89. showed that the incidence of disabilities was 44.7/1,000 persons/year for women and 25.2/1,000 persons/year for men.

The relationship between functional disability and mortality in older people has been addressed in national ²³23. Cavalcanti ACM, Guerra RO. Limitação funcional e sobrevida de idosos na comunidade. Rev Assoc Med Bras 2008; 54:347-52.^,2424. Nascimento CM, Oliveira C, Firmo JOA, Lima-Costa MF, Peixoto SV. Prognostic value of disability on mortality: 15-year follow-up of the Bambuí cohort study of aging. Arch Gerontol Geriatr 2018; 74:112-7.^,2525. Ono LM. Capacidade funcional como preditor de mortalidade em idosos de Florianópolis: estudo Epifloripa idoso [Master's Thesis]. Florianópolis: Universidade Federal de Santa Catarina; 2015. and international ²⁶26. Reuben D, Rubenstein L, Hirsch SH, Hays RD, Reuben DB. Value of functional status as a predictor of mortality: results of a prospective study. Am J Med 1992; 93:665-9.^,2727. John PDS, Tyas SL, Menec V, Tate R. Multimorbidity, disability, and mortality in community-dwelling older adults. Can Fam Physician 2014; 60:e272-80.^,2828. Ankuda CK, Freedman VA, Covinsky KE, Kelley AS. Population-based screening for functional disability in older adults. Innov Aging 2020; 5:igaa065.^,2929. Wei MY, Kabeto MU, Galecki AT, Langa KM. Physical functioning decline and mortality in older adults with multimorbidity: joint modeling of longitudinal and survival data. J Gerontol A Biol Sci Med Sci 2019; 74:226-32. studies. Morbidities, in addition to being the main cause of death in this age group ³⁰30. Lima MG, MBA B, César CLG, Goldbaum M, Carandina L, Ciconelli RM. Impact of chronic disease on quality of life among the elderly in the state of São Paulo, Brazil: a population-based study. Rev Panam Salud Pública 2009; 25:314-35., considerably influence physical functioning ³¹31. Camargo ABM, Dias EC, Castro MHG, Nogueira MJC, Watanabe MI, Torres HG, et al. Idosos e mortalidade: preocupante relação com as causas externas. 1ª Análise SEADE 2016; (35):1-20.. However, disabilities can increase the risk of premature death due to limited mobility, causing changes in the metabolism and functioning of the cardiovascular, respiratory, musculoskeletal and gastrointestinal systems ³²32. Fleury F, Santos-Júnior U, Terra D, Nonato T, Sales F, Cavalcante A, et al. Consequences of immobilization and disuse: a short review. International Journal of Basic and Applied Sciences 2013; 2:297-302.^,3333. Trinity JD, Drummond MJ, Fermoyle C, Mckenzie AI, Supiano MA, Richardson RS. Cardiovasomobility: an integrative understanding of how disuse impacts cardiovascular and skeletal muscle health. J Appl Physiol 2022; 132:835-61.. Moreover, disabilities can reduce well-being by causing dependence, restricting autonomy and individual freedom, and affecting social relations ³⁴34. Pinto JM, Neri AL. Factors related to low social participation in older adults: findings from the Fibra study, Brazil. Cad Saúde Colet (Rio J.) 2017; 25:286-93.. These factors have a substantial effect on satisfaction with life and can diminish well-being and happiness ⁵5. Lima MG, Barros MBA, Alves MCGP. Sentimento de felicidade em idosos: uma abordagem epidemiológica, ISA-Camp 2008. Cad Saúde Pública 2012; 28:2280-92.^,3535. Lima MG, Belon AP, Barros MBA. Happy life expectancy among older adults: differences by sex and functional limitations. Rev Saúde Pública 2016; 50:64.. However, we found no studies exploring the extent to which the feeling of happiness may mediate the association between functional disability and mortality.

Happiness is the degree to which an individual favorably assesses the overall quality of their life ³⁶36. Veenhoven R. Healthy happiness: effects of happiness on physical health and the consequences for preventive health care. J Happiness Stud 2008; 9:449-69.. A low frequency of happiness is also correlated with an increased risk of premature death ³⁷37. Diener E, Chan MY. Happy people live longer: subjective well-being contributes to health and longevity. Appl Psychol Health Well Being 2011; 3:1-43.. Longitudinal studies have stressed the importance of happiness and optimism in preventing morbidities ³⁸38. Kubzansky LD, Sparrow D, Vokonas P, Kawachi I. Is the glass half empty or half full? A prospective study of optimism and coronary heart disease in the normative aging study. Psychosom Med 2001; 63:910-6., adopting healthier behaviors ³⁹39. Baruth M, Lee DC, Sui X, Church TS, Marcus BH, Wilcox S, et al. Emotional outlook on life predicts increases in physical activity among initially inactive men. Health Educ Behav 2011; 38:150-8. and increasing longevity ⁴⁰40. Steptoe A, Deaton A, Stone AA. Subjective wellbeing, health, and ageing. Lancet 2015; 385:640-8.^,4141. Pressman SD, Cohen S. Does positive affect influence health? Psychol Bull 2005; 131:925-71.. Thus, there is a need to clarify associations between the feeling of happiness and health conditions. A deeper understanding of underlying mechanisms will enable knowledge that can guide clinical strategies and policies that seek to ensure wellbeing and extend longevity in the older population.

This study aimed to investigate survival and risk of death within a 10-year period and associate these aspects with functional disability and happiness in older people, analyzing the possible mediating effect of happiness in the association between physical functioning and mortality. Previous studies indicate that the impact of functionality and happiness on mortality can vary significantly between men and women, as well as across different age groups ⁴²42. Beltrán-Sánchez H, Andrade FCD. Educational and sex differentials in life expectancies and disability-free life expectancies in São Paulo, Brazil, and urban areas in Mexico. J Aging Health 2013; 25:815-38.^,4343. Moreno X, Albala C, Lera L, Sánchez H, Fuentes-García A, Dangour AD. The role of gender in the association between self-rated health and mortality among older adults in Santiago, Chile: a cohort study. PLoS One 2017; 12:e0181317.. Stratified analyses by sex and age were conducted to identify specific patterns within these subpopulations (Campinas, São Paulo State, Brazil, 2008-2018).

Material and methods

A retrospective, longitudinal study (ISA-Camp Cohort) was carried out using data from the Health Survey in Campinas (ISA-Camp), conducted from 2008 to 2009, in which 1,519 older people were interviewed. The 2008/2009 ISA-Camp had a complex sampling design with probabilistic cluster sampling in two stages: census sectors and households ⁴⁴44. Alves MCGP. ISA-CAMPINAS 2008/09. Plano de amostragem. https://www.fcm.unicamp.br/fcm/sites/default/files/plano_de_amostragem.pdf (accessed on 17/May/2023).
https://www.fcm.unicamp.br/fcm/sites/def... . A total of 50 census sectors were randomly selected with probability proportional to the number of households, followed by the systematic selection of households in each selected census sector. These sectors were ordered by the percentage of heads of households with complete tertiary education.

Databanks of the Brazilian Mortality Information System (SIM, acronym in Portuguese) of the Campinas Municipal Health Department were searched to obtain information on older people who had answered questionnaire of the 2008/2009 ISA-Camp and died between 2008 and 2018. Deterministic, probabilistic linkage was performed in the databanks with the Stata 15.0 statistical program (https://www.stata.com) considering name, sex and date of birth. Paired records denoted deaths and unpaired records denoted non-deaths. To confirm non-deaths, an active search (telephone contact) was conducted. When such contact was not possible, visits to the households were made to confirm the status of the individual (death/non-death).

The interviewers received training, which involved meetings and orientation on how to communicate with residents via telephone and in-person, as well as with family members and acquaintances (when the individual was not located), to minimize losses. Individuals not found after three attempts at telephone contact and three unsuccessful visits were considered losses and excluded from the analyses. A total of 219 losses occurred − 202 individuals were not found; information was incomplete for six deaths (missing year of death) and 11 individuals did not answer the Short Form (36) Health Survey (SF-36) questionnaire. The final sample consisted of 1,300 individuals, of which 855 remained alive and 445 died.

Variables

The dependent variable was time until death, which was determined by subtracting the date of death from the date of the interview. Information on non-death up to December 31st, 2018 was censored.

Primary independent variables were functional disability (no disability, mild/moderate limitation or severe limitation) and subjective well-being (frequency of feeling of happiness). Functional disability and happiness are the main exposures of interest. Additionally, sex, age (60-74 years and 75 years or older), schooling (0-3, 4-7, and 8 or more years of study), and the number of chronic diseases (none, one, and two or more) were included in the model for adjustment purposes.

Indicators on functional disability used in this study were walking more than one kilometer (F03g), walking several blocks (several hundreds of meters) (F03h), walking one block (100 meters) (F03i) and bathing or dressing (F03j). These four items are part of the SF-36 questionnaire ⁴⁵45. Ware JE, Kosinski M, Bjorner JB, Turner-Bowker DM, Gandek B, Maruish ME. User's manual for the 36v2 Health Survey. 2nd Ed. Lincoln: Quality Metric Incorporated; 2007. and these indicators were also used on previous Brazilian studies with similar items to classify different degrees of functional disability ⁴⁶46. Camargos MCS, Machado CJ, Rodrigues RN. Life expectancy among elderly Brazilians in 2003 according to different levels of functional disability. Cad Saúde Pública 2008; 24:845-52.^,4747. Parahyba MI, Veras R, Melzer D. Disability among elderly women in Brazil. Rev Saúde Pública 2005; 39:383-91.. Individuals who answered “yes” to items F03g and/or F03h but “no” to items F03i and/or F03j were considered to have mild/moderate limitations. Those who answered “yes” to items F03i and F03j were considered to have severe limitations. For analysis purposes, these categories were combined, and participants were classified as follows: (0) without disability, (1) mild/moderate or (2) severe functional disability. Dichotomous variables (0) without disability and (1) with disability (encompassing mild/moderate and severe disability) were used for mediation analysis.

The indicator of frequency of the feeling of happiness was the answer to the following question: “How often have you felt happy in the last four weeks?” Response categories were dichotomized as “always” or “most of the time” (scored 0, greater frequency of happiness) and “a small part of the time” or “never” (scored 1, lower frequency of happiness). This indicator has been used ⁴⁸48. Rizzato M, Di Dio C, Miraglia L, Sam C, D'Anzi S, Antonelli M, et al. Are you happy? a validation study of a tool measuring happiness. Behav Sci (Basel) 2022; 12:295.^,4949. Andreoni J, Douglas Bernheim B, Jia T. Do people report happiness accurately? http://www.nber.org/papers/w32208 (accessed on 17/May/2023).
http://www.nber.org/papers/w32208... ^,5050. Barattucci M, Brugnera A, Ramaci T, Kuvacic G, De Giorgio A. An 8-item scale for the measurement of happiness: validation and application of the Oxford happiness questionnaire in an Italian sample. Curr Psychol 2024; 43:11092-101.^,5151. Shen Y, Yuan S, Liu J, Sun B, Chen Z, Zheng L, et al. The reliability, validity and screening effect of the happiness index scale among inpatients in a general hospital. BMC Psychiatry 2022; 22:601. to assess subjective well-being and is considered a valid and direct measure of happiness ⁵5. Lima MG, Barros MBA, Alves MCGP. Sentimento de felicidade em idosos: uma abordagem epidemiológica, ISA-Camp 2008. Cad Saúde Pública 2012; 28:2280-92.^,4141. Pressman SD, Cohen S. Does positive affect influence health? Psychol Bull 2005; 131:925-71.. For analysis purposes, participants were categorized as having a higher or lower frequency of happiness based on their responses. All independent variables were collected at baseline.

Data analysis

Percentages of deaths in the period were estimated according to physical functioning and feeling of happiness in the overall sample, as well as stratified by sex and age group. Survival analyses were performed with the Kaplan-Meier estimator according to physical functioning and well-being. The log-rank test was used to compare the curves, considering a 5% significance level. Cox semiparametric regression models were run for the estimates of associations between each independent variable and dependent variables, estimating hazard ratios (HR).

Odds ratios (OR) were also estimated using multiple binary logistic regression to determine associations between mortality and both functional disability and the feeling of happiness. Mediation analysis was then conducted using happiness as a possible mediator of the association between functional disability and mortality. The Karlson-Holm-Breen (KHB) method ⁵²52. Breen R, Karlson KB, Holm A. total, direct, and indirect effects in logit and probit models. Sociol Methods Res 2013; 42:164-91. with a 5% significance level was used to estimate total and direct effects of functional disability on mortality, as well as the mediation percentage. The KHB method decomposes the OR and estimates the percentage of the mediator in the association ⁵²52. Breen R, Karlson KB, Holm A. total, direct, and indirect effects in logit and probit models. Sociol Methods Res 2013; 42:164-91.. We previously tested possible interaction effects of mediator versus exposure in the association and did not find significant results at the 5% level.

To control for confounding, the following variables were incorporated into the multiple regression and KHB models: sex, age, schooling and chronic diseases. The choice of these adjustment variables was made based on the analysis of directed acyclic graphs ⁵³53. Suttorp MM, Siegerink B, Jager KJ, Zoccali C, Dekker FW. Graphical presentation of confounding in directed acyclic graphs. Nephrol Dial Transplant 2015; 30:1418-23..

The Stata 15.0 software program was used. Cox regression, logistic regression, and KHB analyses were conducted using the survey module, which incorporates the complex sampling plan of the 2008/2009 ISA-Camp. The analysis of residuals was performed to determine the goodness-of-fit of the Cox model. Schoenfeld’s test and global proportionality analyses were performed.

Ethical aspects

The 2008/2009 ISA-Camp and ISA-Camp Cohort study received approval from the Human Research Ethics Committee of the School of Medical Sciences of the University of Campinas (approval n. 079/2007 and 1.650.093/2018, respectively). This study received approval from the local research ethics committee (n. 6.276.539/2023).

Results

Median age was 69 years in the overall sample (n = 1,300). A total of 61.7% of the 855 living individuals were women. A total of 52% of participants were aged 60-69 years; 79.9% self-declared as white; 82.3% had a monthly income of less than three minimum wages; and 70.8% had less than eight years of schooling (data not presented).

Table 1 shows the mortality rate was 27.3% (95%CI: 24.1-30.8) among individuals without functional disability, 39.8 (95%CI: 33.7-46.2) among those who reported mild to moderate limitation and 65.4% (95%CI: 55.3-74.3) among those who reported severe functional disability. Regarding the frequency of the feeling of happiness, the mortality rate was 30.6% (95%CI: 26.9-34.5) among those who reported feeling happy most of the time/always and 45.7% (95%CI: 39.9-51.5) among those who reported feeling happy only a small part of the time/never. These results show a dose-response gradient for both functional disability and the feeling of happiness.

In the analyses stratified by sex and age group, we observed that the mortality rate was higher among men with no limitations (31.7%; 95%CI: 26.8-37.1) compared to women with no limitations (23.2%; 95%CI: 19.7-27.2). On the other hand, no difference between sexes was found among individuals with severe limitation when considering confidence intervals. Notably, this finding suggests that the distinct experience of mortality between sexes disappears when considering individuals with severe limitations. The same pattern was not observed in the analysis of the feeling of happiness. In the younger age group (60-74 years), severe limitations substantially increased the mortality rate among men and women compared to those without limitations. In the older age group (75 years or older), severe limitations increased the mortality rate only among women. Considering the category of lower frequency of happiness in both age groups, the mortality rate was higher only among women (Table 2).

The results of the Kaplan-Meier analysis (Figures 1a and 1b) showed that survival rates were lower for individuals with severe functional limitations and those reporting lower frequency of happiness. The differences between categories were statistically significant (p < 0.05).

For physical functioning, 50% of deaths occurred within 5.2 years of follow-up among those with severe limitation, and 5.9 years among those without limitations. Regarding the feeling of happiness, 50% of deaths occurred within 5.6 years of follow-up among those who reported always or almost always feeling happy, and 4.6 years among those who reported never or almost never feeling happy (data not presented).

Table 3 (survival analysis) shows the associations between physical functioning/feeling of happiness and mortality. In the unadjusted analysis, risk of death was greater in the population with mild to moderate limitation (HR = 1.62; 95%CI: 1.29-2.03) and severe limitation (HR = 3.69; 95%CI: 2.76-4.95) compared to those with no limitations. In the model adjusted by sex, age, schooling and chronic diseases, the risk of death remains greater, with association gradient, among individuals with mild to moderate limitation (HR = 1.34; 95%CI: 1.03-1.76) and severe functional limitation (HR = 2.79; 95%CI: 2.04-3.81), compared to those with no limitations. In the unadjusted analysis, the report of happiness for a small part of the time or never increased the risk of death by 71% (HR = 1.71; 95%CI: 1.35-2.18) compared to the reference category. In the adjusted model, the risk of death was 60% greater among those who reported feeling happy a small part of the time or never (HR = 1.60; 95%CI: 1.26-2.03) compared to those who reported feeling happy more often. The results of Schoenfeld’s and global proportionality analyses demonstrated the model fit the data well.

In the binary logistic regression analysis, functional disabilities increased the likelihood of a less frequent feeling of happiness by 2.29 times (OR = 2.29; 95%CI: 1.73-3.05) and mortality was more likely in the population with a less frequent feeling of happiness (OR = 1.79; 95%CI: 1.34-2.40). In the KHB analysis, the OR was 1.72 (95%CI: 1.31-2.47) for the total effect of functional disability on death and 1.59 (95%CI: 1.21-2.09) for the direct effect. The mediating percentage of the lower frequency of the feeling of happiness in the association between physical functioning and mortality was 14.1% (Figure 2).

Discussion

This study demonstrated lower survival rates among older people as limitations increase in relation to physical functioning and those who reported having feelings of happiness for a small part of the time or never. Moreover, a low frequency of happiness was a mediating factor in the association between functional disability and mortality. These findings underscore the influence of both physical functioning and subjective well-being on longevity.

Recent studies have highlighted the intricate link between functional disability ²⁴24. Nascimento CM, Oliveira C, Firmo JOA, Lima-Costa MF, Peixoto SV. Prognostic value of disability on mortality: 15-year follow-up of the Bambuí cohort study of aging. Arch Gerontol Geriatr 2018; 74:112-7.^,2626. Reuben D, Rubenstein L, Hirsch SH, Hays RD, Reuben DB. Value of functional status as a predictor of mortality: results of a prospective study. Am J Med 1992; 93:665-9.^,2727. John PDS, Tyas SL, Menec V, Tate R. Multimorbidity, disability, and mortality in community-dwelling older adults. Can Fam Physician 2014; 60:e272-80.^,2929. Wei MY, Kabeto MU, Galecki AT, Langa KM. Physical functioning decline and mortality in older adults with multimorbidity: joint modeling of longitudinal and survival data. J Gerontol A Biol Sci Med Sci 2019; 74:226-32.^,5454. Andrade FCD, Guevara PE, Lebrão ML, De Oliveira Duarte YA. Correlates of the incidence of disability and mortality among older adult Brazilians with and without diabetes mellitus and stroke. BMC Public Health 2012; 12:361., subjective well-being ³⁷37. Diener E, Chan MY. Happy people live longer: subjective well-being contributes to health and longevity. Appl Psychol Health Well Being 2011; 3:1-43.^,4040. Steptoe A, Deaton A, Stone AA. Subjective wellbeing, health, and ageing. Lancet 2015; 385:640-8.^,4141. Pressman SD, Cohen S. Does positive affect influence health? Psychol Bull 2005; 131:925-71., and mortality in older adults, which are in line with our findings. For instance, Steptoe et al. ⁴⁰40. Steptoe A, Deaton A, Stone AA. Subjective wellbeing, health, and ageing. Lancet 2015; 385:640-8. demonstrated that lower levels of subjective wellbeing are associated with increased mortality risk, even after controlling for physical health and other confounders. In recent findings from the Brazilian Longitudinal Study of Aging (ELSI-Brazil), Macinko et al. ⁵⁵55. Macinko J, Beltrán-Sánchez H, Mambrini JVM, Lima-Costa MF. Socioeconomic, disease burden, physical functioning, psychosocial, and environmental factors associated with mortality among older adults: the Brazilian Longitudinal Study of Ageing (ELSI-Brazil). J Aging Health 2024; 36:25-34. also demonstrated significant associations of physical functioning, psychosocial and environmental factors with mortality among older adults. Specifically, having any functional limitations were associated with higher mortality risk. These findings provide crucial insights into the multifaceted nature of aging and mortality and support the need for comprehensive health strategies that address physical and psychosocial factors to promote healthy aging ⁵⁵55. Macinko J, Beltrán-Sánchez H, Mambrini JVM, Lima-Costa MF. Socioeconomic, disease burden, physical functioning, psychosocial, and environmental factors associated with mortality among older adults: the Brazilian Longitudinal Study of Ageing (ELSI-Brazil). J Aging Health 2024; 36:25-34..

Functional disability in older adults is strongly associated with increased mortality due to several interrelated factors. Firstly, functional disability often leads to decreased physical activity, which contributes to the progression of chronic diseases such as cardiovascular diseases, diabetes, and obesity, ultimately increasing the risk of death ⁵⁶56. Veronese N, Cereda E, Stubbs B, Solmi M, Luchini C, Manzato E, et al. Risk of cardiovascular disease morbidity and mortality in frail and pre-frail older adults: results from a meta-analysis and exploratory meta-regression analysis. Ageing Res Rev 2017; 35:63-73.. Secondly, individuals with functional disabilities may experience a decline in social participation, leading to isolation and increased vulnerability to mental health disorders like depression, which has been linked to higher mortality rates ⁵⁷57. Lennartsson C, Rehnberg J, Dahlberg L. The association between loneliness, social isolation and all-cause mortality in a nationally representative sample of older women and men. Aging Ment Health 2022; 26:1821-8.. Moreover, functional disability may impair the ability to perform activities of daily living, increasing the likelihood of adverse events such as falls, infections, and malnutrition, all of which significantly contribute to mortality ⁵⁸58. Boyd CM, Landefeld CS, Counsell SR, Palmer RM, Fortinsky RH, Kresevic D, et al. Recovery of activities of daily living in older adults after hospitalization for acute medical illness. J Am Geriatr Soc 2008; 56:2171-9.. These interconnected factors highlight the importance of maintaining functional capacity to increase survival among older adults.

The association between happiness and mortality has been documented in international studies ⁴⁰40. Steptoe A, Deaton A, Stone AA. Subjective wellbeing, health, and ageing. Lancet 2015; 385:640-8.^,4141. Pressman SD, Cohen S. Does positive affect influence health? Psychol Bull 2005; 131:925-71.. In a study involving a representative sample of the British population, researchers found a significant reduction in the risk of premature death throughout the follow-up period among older people who reported better subjective well-being ⁴⁰40. Steptoe A, Deaton A, Stone AA. Subjective wellbeing, health, and ageing. Lancet 2015; 385:640-8.. This protective effect of happiness remained significant even after controlling for age, sex, socioeconomic status and preexisting health conditions. A systematic review and meta-analysis investigated the effect of positive feelings, including happiness, on health and mortality in longitudinal studies ⁴¹41. Pressman SD, Cohen S. Does positive affect influence health? Psychol Bull 2005; 131:925-71.. The results showed that greater positive affectivity was associated with a significant reduction in the risk of premature mortality in older people regardless of age, sex, physical health, and behavioral risk factors.

With additional years of life, older people have a greater chance of experiencing important moments, such as celebrating birthdays, participating in family events, achieving personal goals and sharing knowledge with younger generations, thus preserving culture and history ³⁷37. Diener E, Chan MY. Happy people live longer: subjective well-being contributes to health and longevity. Appl Psychol Health Well Being 2011; 3:1-43.. Happier older people tend to have better physical and mental health, as happiness is associated with decreased chronic health problems, as well as greater resilience, hope and harmony ⁵⁹59. Singh S, Kshtriya S, Valk R. Health, hope, and harmony: a systematic review of the determinants of happiness across cultures and countries. Int J Environ Res Public Health 2023; 20:3306.. Optimism and positivity can positively influence the immune system and reduce stress and anxiety, being associated with a healthier lifestyle (such as healthier eating habits, practicing regular physical exercises) and avoiding harmful behaviors (such as smoking and excessive alcohol intake) ⁵5. Lima MG, Barros MBA, Alves MCGP. Sentimento de felicidade em idosos: uma abordagem epidemiológica, ISA-Camp 2008. Cad Saúde Pública 2012; 28:2280-92.^,6060. Boehm JK, Kubzansky LD. The heart's content: the association between positive psychological well-being and cardiovascular health. Psychol Bull 2012; 138:655-91.. Happiness is also associated with a solid social support network. Older people who feel loved, supported and connected to their families, friends and community have a greater sense of purpose and meaning of life, which can contribute to greater longevity ⁶¹61. Rueda-Salazar S, Spijker J, Devolder D, Albala C. The contribution of social participation to differences in life expectancy and healthy years among the older population: a comparison between Chile, Costa Rica and Spain. PLoS One 2021; 16:e0248179.. Mental health conditions can also influence health-related decision-making, such as adhering to medical treatment and searching for preventive healthcare. Lack of motivation resulting from a greater frequency of unhappy moments can trigger behaviors and reactions that increase the risk of health complications and, consequently, premature death ⁶²62. Berkman LF, Kawaichi I, Glymour MM. Social epidemiology. 2nd Ed. New York: Oxford University Press; 2014..

A strong association was found between physical functioning and the feeling of happiness, which is in line with previous studies ⁵5. Lima MG, Barros MBA, Alves MCGP. Sentimento de felicidade em idosos: uma abordagem epidemiológica, ISA-Camp 2008. Cad Saúde Pública 2012; 28:2280-92.^,3535. Lima MG, Belon AP, Barros MBA. Happy life expectancy among older adults: differences by sex and functional limitations. Rev Saúde Pública 2016; 50:64.. A possible explanation for these findings is the reduction in independence, autonomy and freedom in the population living with functional limitations, which can trigger feelings of anguish, unsatisfaction and unhappiness. Moreover, a lower frequency of happiness was a mediator in the negative impact of functional disability on mortality, as a lower frequency of happy moments increased the risk of premature death by 14% in the older population living with disabilities. These findings underscore the need to care for older people with limitations, not only regarding physical aspects, but also given the impact of such conditions on mental health. These relationships also illustrate how emotional dimensions can have profound repercussions in various spheres of health. By considering a lower frequency of happiness a mediating factor in the negative impact of functional disability on longevity, one recognizes that emotions can shape physiological and behavioral aspects in a tangible way ⁶³63. Herman AM, Critchley HD, Duka T. The role of emotions and physiological arousal in modulating impulsive behaviour. Biol Psychol 2018; 133:30-43..

Limitations and strengths

Caution is needed when interpreting the association between the feeling of happiness and functional disability, as the study design does not allow for causal inferences. Functional disability develops over the life course of older adults, whereas happiness is a momentary feeling, suggesting that disabilities are more likely to lead to unhappiness, rather than the inverse. We also recognize the limitation of not using specific validated scales to measure functional disability; instead, we relied on items from the SF-36 questionnaire. Similarly, we did not use a specific scale to measure happiness, opting for a single question about frequency of the feeling of happiness over the past four weeks, with five possible response categories, which is suitable for large-scale studies ⁶⁴64. Diener E. Subjective well-being. Psychol Bull 1984; 95:542-75.. Evaluating the frequency of happiness rather than its intensity provides a significant advantage, as frequency is more likely to capture the stability of subjective well-being over time ⁵5. Lima MG, Barros MBA, Alves MCGP. Sentimento de felicidade em idosos: uma abordagem epidemiológica, ISA-Camp 2008. Cad Saúde Pública 2012; 28:2280-92.^,6464. Diener E. Subjective well-being. Psychol Bull 1984; 95:542-75.^,6565. Diener E. Subjective well-being. The science of happiness and a proposal for a national index. Am Psychol 2000; 55:34-43..

Notably, this study also has strengths. We used a representative sample of the population of Campinas studied over a 10-year period with fundamental variables for the control of confounding. Moreover, this study offers unprecedented results in Brazil and Latin America. No cohort studies were found in the Brazilian literature that directly address the relationship between happiness and mortality in older people. The continuity of research in this field could lead to a deeper understanding of mechanisms underlying this association and enable the generalization of these results to different cultural and socioeconomic contexts.

Health care, clinical and policy implications

This study underscores the importance of good physical functioning and happiness in the longevity of individuals aged 60 years or older, revealing the role of happiness in the association between physical functioning and mortality.

Providing care for older people with a multidisciplinary team, including physical therapy and psychotherapy sessions, is essential, with special attention to low-income populations and those served by the Brazilian Unified National Health System (SUS) to ensure the incorporation of these strategies into their care. It is also crucial to emphasize the importance of remaining physically and mentally active throughout life to promote better health outcomes in old age. The incorporation of indicators of physical limitations and well-being, including happiness, into the health diagnosis of older people could contribute to creating clinical and policy strategies. Thus, it will be possible not only to improve the quality of life of older people, but also to promote greater longevity, reinforcing the importance of a comprehensive health approach that considers the various dimensions of health, especially physical and emotional aspects.

Acknowledgments

The authors thank the Collaborating Center for Health Situation Analysis (CCAS), the Brazilian National Research Council (CNPq), the Brazilian Coordination for the Improvement of Higher Education Personnel (CAPES), the Campinas Municipal Health Department and the Brazilian Ministry of Health.

References

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