Abstract

Introduction

Among the disabling syndromes, dementia is one of the leading causes of functional impairment and declining quality of life in the elderly ¹1. World Health Organization. Dementia: a public health priority. Geneva: World Health Organization; 2012.. According to the most recent report by the World Health Organization, more than 35 million persons in the world presented some degree of dementia, a number that may triple by the year 2050, affecting more than 115 million persons ¹1. World Health Organization. Dementia: a public health priority. Geneva: World Health Organization; 2012.. Approximately 60% of cases of dementia occur in low and medium-income countries, posing a major challenge for healthcare planning due to the economic and social impact of this group of diseases on governments and family members ¹1. World Health Organization. Dementia: a public health priority. Geneva: World Health Organization; 2012.. Caregivers and family members frequently suffer depressive symptoms due to the overload of chores and burnout, negatively affecting their physical and psychological health, quality of life, and life expectancy ¹1. World Health Organization. Dementia: a public health priority. Geneva: World Health Organization; 2012.. Thus, the identification of factors impacting the prevention and treatment of these diseases has raised growing interest among researchers.

According to the evidence, heavier demand on functional capacities over the course of life exerts a protective effect on the health of the elderly, postponing potential functional alterations resulting from cognitive decline²2. Valenzuela MJ, Sachdev P. Assessment of complex mental activity across the lifespan: development of the Lifetime of Experiences Questionnaire (LEQ). Psychol Med 2007, 37:1015-25.. The literature shows that elderly that maintain normal cognitive performance are younger ³3. Hendrie HC, Albert MS, Butters MA, Gao S, Knopmen DS, Launer LJ, et al. The NIH cognitive and emotional health project: report of the critical evaluation study committee. Alzheimers Dement 2006; 2:12-32., have higher levels of schooling and income ¹1. World Health Organization. Dementia: a public health priority. Geneva: World Health Organization; 2012.,⁴4. Williams JW, Plassman BL, Burke J, Holsinger T, Benjamin S. Preventing Alzheimer's disease and cognitive decline. Rockville: U.S. Department of Health and Human Services, Agency for Healthcare Research and Quality; 2010. (Evidence Report/Technology Assessment, 193)., display higher levels of community participation ⁵5. Barnes DE, Cauley JE, Lui L-Y, Fink HA, McCulloch C, Stone KL, et al. Women who maintain optimal cognitive function into old age. J Am Geriatr Soc 2007; 55:259-64., and perform activities that involve physical, mental, and social stimulation⁶6. Yaffe K, Fiocco AJ, Lindquist K, Vittinghoff E, Simonsick EM, Newman AB. Predictors of maintaining cognitive function in older adults: the Health ABC Study. Neurology 2009; 72:2029-35.. In addition, alterations in functional capacity can precede cognitive impairment ⁷7. Yeh YC, Lin KN, Chen WT, Lin CY, Chen TB, Wang PN. Functional disability profiles in amnestic mild cognitive impairment. Dement Geriatr Cogn Disord 2011; 31:225-32.,⁸8. Njegovan V, Hing MM, Mitchell SL, Molnar FJ. The hierarchy of functional loss associated with cognitive decline in older persons. J Gerontol A Biol Sci Med Sci 2001; 56:638-43..

Functional status is commonly defined as the performance of activities of daily living. These can be divided didactically into three groups of activities: basic – daily tasks directly related to survival; instrumental – tasks involved in maintaining life in community; and advanced – more complex activities, subdivided into the physical, leisure-time, social, and productive domains, requiring higher levels of cognitive, physical, and social functions and that are influenced by motivational and cultural patterns ⁹9. Dias EG, Duarte YAO, Almeida MHM, Lebrão ML. Caracterização das atividades avançadas de vida diária (AAVDS): um estudo de revisão. Rev Ter Ocup 2011; 22:45-51..

Advanced activities of daily living (AADL) are based on intentional conducts involving the physical, mental, and social functioning that allow the individual to develop multiple social roles and maintain good mental health and quality of life ¹⁰10. Reuben DB, Solomon DH. Assessment in geriatrics: of caveats and names. J Am Geriatr Soc 1989; 37:570-2.,¹¹11. Reuben DB, Laliberte L, Hiris J, Mor V. A hierarchical exercise scale to measure function at the advanced activities of daily living (AADL) level. J Am Geriatr Soc 1990; 38:855-61..

Cognitive decline is associated with a specific pattern of functional losses, beginning with impaired performance of AADL, followed by losses in instrumental activities of daily living (IADL) and progressing to basic activities of daily living (BADL) ¹²12. De Vriendt P, Gorus E, Cornelis E, Velghe A, Petrovic M, Mets T. The process of decline in advanced activities of daily living: a qualitative explorative study in mild cognitive impairment. Int Psychogeriatr 2012; 24:974-86.,¹³13. De Vriendt P, Gorus E, Cornelis E, Velghe A, Petrovic M, Mets T. The advanced activities of daily living: a tool allowing the evaluation of subtle functional decline in mild cognitive impairment. J Nutr Health Aging 2013; 17:64-71.. Thus, some studies suggest that minor alterations in the performance of AADL are the first signs of mild cognitive impairments ¹²12. De Vriendt P, Gorus E, Cornelis E, Velghe A, Petrovic M, Mets T. The process of decline in advanced activities of daily living: a qualitative explorative study in mild cognitive impairment. Int Psychogeriatr 2012; 24:974-86.,¹³13. De Vriendt P, Gorus E, Cornelis E, Velghe A, Petrovic M, Mets T. The advanced activities of daily living: a tool allowing the evaluation of subtle functional decline in mild cognitive impairment. J Nutr Health Aging 2013; 17:64-71.,¹⁴14. Perneczky R, Pohl C, Sorg C, Hartmann J, Komossa K, Alexopoulos P, et al. Complex activities of daily living in mild cognitive impairment: conceptual and diagnostic issues. Age Ageing 2006; 35:240-5.. AADL, also known as complex activities of daily living, require multiple intact physical, psychological, social, and cognitive functions for their performance and involve activities within dimensions of participation in social, productive, and leisure-time activities, such as: skills to maintain working and planning trips, participation in community groups or movements, driving, planning events, or playing games ¹⁰10. Reuben DB, Solomon DH. Assessment in geriatrics: of caveats and names. J Am Geriatr Soc 1989; 37:570-2.,¹¹11. Reuben DB, Laliberte L, Hiris J, Mor V. A hierarchical exercise scale to measure function at the advanced activities of daily living (AADL) level. J Am Geriatr Soc 1990; 38:855-61.,¹²12. De Vriendt P, Gorus E, Cornelis E, Velghe A, Petrovic M, Mets T. The process of decline in advanced activities of daily living: a qualitative explorative study in mild cognitive impairment. Int Psychogeriatr 2012; 24:974-86.,¹³13. De Vriendt P, Gorus E, Cornelis E, Velghe A, Petrovic M, Mets T. The advanced activities of daily living: a tool allowing the evaluation of subtle functional decline in mild cognitive impairment. J Nutr Health Aging 2013; 17:64-71..

Longitudinal studies in Brazil ¹⁵15. D'Orsi E, Xavier AJ, Ramos LR. Trabalho, suporte social e lazer protegem idosos da perda funcional: Estudo Epidoso. Rev Saúde Pública 2011; 45: 685-92.,¹⁶16. Di Rienzo VD. Participação em atividades e funcionamento cognitivo: estudo de coorte com idosos residentes em área de baixa renda no Município de São Paulo [Tese de Doutorado]. São Paulo: Faculdade de Medicina, Universidade de São Paulo; 2009. have reported a significant association between performance of social, productive, physical, and leisure-time activities and maintenance of functional capacity and cognitive functioning. Other studies ¹²12. De Vriendt P, Gorus E, Cornelis E, Velghe A, Petrovic M, Mets T. The process of decline in advanced activities of daily living: a qualitative explorative study in mild cognitive impairment. Int Psychogeriatr 2012; 24:974-86.,¹³13. De Vriendt P, Gorus E, Cornelis E, Velghe A, Petrovic M, Mets T. The advanced activities of daily living: a tool allowing the evaluation of subtle functional decline in mild cognitive impairment. J Nutr Health Aging 2013; 17:64-71. have shown an association between cognitive decline and performance of AADL, but most of the evidence comes from cross-sectional studies, and there are few studies on this subject, thus hindering the establishment of causal relations between these factors. The current study thus aimed to investigate the impact of performance of AADL on the incidence of cognitive decline in a representative sample of community-living elderly in the city of São Paulo, Brazil.

Methods

A longitudinal study was performed with data from the SABE Study (Health, Well-Being, and Aging) collected in the years 2006 and 2010.

Study population and sample

The SABE Study was launched in 2000 under the coordination of the Pan-American Health Organization (PAHO) and was developed in seven cities in Latin America and the Caribbean: Buenos Aires (Argentina), Bridgetown (Barbados), Havana (Cuba), Montevideo (Uruguay), São Paulo (Brazil), Santiago (Chile), and Mexico City (Mexico), with the objective of drawing a profile of living and health conditions of elderly persons in the region. In Brazil, the study population consisted of a probabilistic sample of elderly living in the urban area of the city of São Paulo in 2000, calculated on the basis of the population count performed in 1996 by the Brazilian Instutute of Geography and Statistics (IBGE Foundation). The final sample in 2000 included 2,143 elderly persons (cohort A) interviewed at home using a standardized questionnaire (http://www.fsp.usp.br/sabe/quetionario.php, accessed on 08/Jan/2013). A second wave of the study was conducted in 2006, when we located and re-interviewed 1,115 elderly persons from the first cohort and added a new cohort of 298 persons 60-64 years of age (cohort B) to maintain the representativeness of these individuals in the sample. The current study considered as its study population the 1,413 individuals interviewed in 2006 (cohorts A + B) that did not present cognitive decline, resulting in an initial sample of 1,152 elderly.

Ethical aspects

As part of the SABE study, the current study was approved by the Institutional Review Board of the School of Public Health, São Paulo University, and all the participants signed a free and informed consent form just prior to the interview.

Study variables

• Dependent variable

Incidence of cognitive decline in 2010 (no/yes) was assessed with the abbreviated version of the Mini-Mental State Examination (MMSE) ¹⁷17. Icaza MG, Albala C. Minimental State Examinations (MMSE) del estudio de demencia en Chile: analisis estadistico. Washington DC: Organización Panamericana de la Salud; 1999.. The instrument has been used for cognitive screening since the first wave of the SABE study. This version was validated in a study by the World Health Organization (WHO) entitledAge-Associated Dementias, for populations with low schooling, with the aim of minimizing possible effects of schooling. The abbreviated MMSE has thirteen items (with a maximum score of 19 points), while the cutoff point used for positive screening of cognitive decline was 12 points or fewer, with sensitivity of 93.8 and specificity of 93.9¹⁷17. Icaza MG, Albala C. Minimental State Examinations (MMSE) del estudio de demencia en Chile: analisis estadistico. Washington DC: Organización Panamericana de la Salud; 1999..

Longitudinal studies have reported a direct association between baseline scores on the MMSE and better cognitive function ¹⁴14. Perneczky R, Pohl C, Sorg C, Hartmann J, Komossa K, Alexopoulos P, et al. Complex activities of daily living in mild cognitive impairment: conceptual and diagnostic issues. Age Ageing 2006; 35:240-5.,¹⁸18. Sobral M, Paúl C. Education, leisure activities and cognitive and functional ability of Alzheimer's disease patients. Dement Neuropsychol 2013; 7: 181-9. and inverse association with cognitive decline in elderly with dementia ¹⁹19. Wilkosz PA, Seltman HJ, Devlin B, Weamer EA, Lopez OL, DeKosky ST, et al. Trajectories of cognitive decline in Alzheimer's disease. Int Psychogeriatr 2010; 22:281-90.,²⁰20. Castro-Costa E, Dewey ME, Uchôa E, Firmo JO, Lima-Costa MF, Stewart R. Trajectories of cognitive decline over 10 years in Brazilian elderly population: the Bambuí Cohort Study of Aging. Cad Saúde Pública 2011; 27 Suppl 3:S345-50., reinforcing the importance of MMSE as a screening test for detecting alterations in cognitive functions. The MMSE shows good accuracy for distinguishing persons with mild Alzheimer from normal controls, but it is not indicated for distinguishing between various subtypes of mild cognitive impairment, thus corroborating the use of other forms of neuropsychological screening and assessment ²¹21. Diniz BS, Nunes PV, Yassuda MS, Pereira FS, Flaks MK, Viola LF, et al. Mild cognitive impairment: cognitive screening or neuropsychological assessment? Rev Bras Psiquiatr 2008; 30:316-21..

The study thus included the elderly from cohorts A and B in 2006 who presented an initial score of more than 12 points on the abbreviated MMSE ¹⁷17. Icaza MG, Albala C. Minimental State Examinations (MMSE) del estudio de demencia en Chile: analisis estadistico. Washington DC: Organización Panamericana de la Salud; 1999.. Incident cases of cognitive decline in 2010 were defined as elderly persons who presented a score below the cutoff point in the study follow-up.

• Target covariate

Performance of AADL was assessed in 2006 using 12 questions involving higher cognitive functions and social participation. Due to the high subjectivity involved in the performance of these activities and the lack of a single instrument for their assessment, the AADL included in the SABE Study were selected from the literature ⁹9. Dias EG, Duarte YAO, Almeida MHM, Lebrão ML. Caracterização das atividades avançadas de vida diária (AAVDS): um estudo de revisão. Rev Ter Ocup 2011; 22:45-51.,¹⁰10. Reuben DB, Solomon DH. Assessment in geriatrics: of caveats and names. J Am Geriatr Soc 1989; 37:570-2.. Domains of activities were thus proposed, aimed at greater comparability of the information. The activities included in this study are representative of the social, productive, and physical/leisure-time domains ⁹9. Dias EG, Duarte YAO, Almeida MHM, Lebrão ML. Caracterização das atividades avançadas de vida diária (AAVDS): um estudo de revisão. Rev Ter Ocup 2011; 22:45-51.,¹⁰10. Reuben DB, Solomon DH. Assessment in geriatrics: of caveats and names. J Am Geriatr Soc 1989; 37:570-2..The following activities were included in 2006: (1) contact with other persons through letters, telephone, or e-mail; (2) visits to friends and family members at their homes; (3) care or assistance to other persons (including personal care, transportation, shopping for family members or friends); (4) volunteer work away from home; (5) trips out of town, staying over at least one night; (6) participation in some regular exercise program (e.g., sports, physical exercise, walks, and groups of physical practices); (7) inviting persons to visit for meals or leisure; (8) going out with others to public places like restaurants or movie theaters; (9) performance of some manual activity, handicrafts, or artistic activity; (10) participation in organized social activities (clubs, community or religious groups, fellowship centers for the elderly, bingo); (11) using the computer, including Internet; (12) driving a motor vehicle. All the questions were answered with a scale with 5 possible answers (always, frequently, occasionally, rarely, and never). The answers always, frequently, and occasionally were defined as performance of the activity. The score obtained by the sum of the performance of activities (always/frequently) varied from 0 to 12 and was considered the target variable.

• Covariates

a) Socio-demographic

Gender (male/female), age bracket (60-74 versus ≥ 75 years), schooling (0-3 years, 4-7 years, ≥ 8), marital status (with or without a partner), living alone (no/yes), income sufficient for basic expenses (no/yes).

b) Health conditions and lifestyle:

Self-rated health was assessed with the question “How do you rate your health: very good, good, fair, bad, or very bad?” The answers very good, good, and fair were regrouped as “good” and bad and very bad were regrouped as “bad”.

The variable number of self-reported diseases was constructed with the questions “Has a doctor or nurse ever told you that you have....?” including the diseases hypertension, diabetes, chronic obstructive pulmonary disease (COPD), heart disease, cerebrovascular diseases, joint disease, and osteoporosis. The final variable was obtained as the sum of the positive answers on the diseases. The answers were reclassified as no disease, one disease, or two or more diseases.

Presence of depressive symptoms was assessed with the abbreviated Geriatric Depression Scale (GDS) ²²22. Almeida OP, Almeida SAA. Confiabilidade da versão brasileira da Escala de Depressão em Geriatria (GDS) versão reduzida. Arq Neuropsiquiatr 1999; 57:421-6.. This scale contains 5 items and is one of the most widely used instruments for detecting severe and mild depressive symptoms in the elderly. Presence of depressive symptoms was defined as ≥ 6 points on the GDS.

Tobacco consumption was assessed with the following question: “Do you now have or have you ever had the habit of smoking?” Answers were categorized as never smoked, currently smokes, or previously smoked but no longer smokes.

Alcohol consumption was based on the geriatric version of the Michigan Alcoholism Screening Test(MAST)²³23. Johnson-Greene D, McCaul ME, Roger P. Screening for hazardous drinking using the Michigan Alcohol Screening Test-Geriatric Version (MAST-G) in elderly persons with acute cerebrovascular accidents. Alcohol Clin Exp Res 2009; 33:1555-61.. The test defines elderly with scores ≤ 1 point as not having a risk of excessive alcohol consumption, while elderly with ≥ 2 points are defined as at risk. Elders that reported drinking alcohol at least once a week were subdivided according to the MAST score, resulting in the final categorization of the variable: no alcohol consumption, social drinking, or alcohol abuse.

Functional performance was obtained as the report of difficulties in performing one or more BADL ²⁴24. Katz S, Ford AB, Moskowitz RW, Jackson BA, Jaffe MW. Studies of illness in the aged. The index of ADL: a standardized measure of biological and psychosocial function. JAMA 1963; 185:914-9. and IADL ²⁵25. Lawton MP, Brody EM. Assessment of older people: self-maintaining and instrumental activities of daily living. Gerontologist 1969; 9:179-86..

Impaired mobility was assessed with the Short Physical Performance Battery (SPPB) ²⁶26. Guralnik JM, Simonsick EM, Ferrucci L, Glynn RJ, Berkman LF, Blazer DG, et al. A short physical performance battery assessing lower extremity function: association with self-reported disability and prediction of mortality and nursing home admission. J Gerontol 1994; 49:M85-94., based on the following three tests: (1) walking three meters at normal speed; (2) getting in and out of a chair as quickly as possible with arms crossed; and (3) static balance (the latter subdivided into standing with feet together, semi-tandem stance, and tandem stance). Each task received a score from 0 (cannot perform) to 4 points (best performance). The final score was obtained as the sum of the scores from the three tests, varying from 0 to 12 points. Mobility performance was classified as moderate/good with 7-12 points and bad/very bad with 0-6 points, indicating impaired mobility.

Statistical analysis

Statistical analysis included measures of frequency, bivariate analysis, and Poisson multivariate regression analysis. Bivariate analysis used the chi-square test with Rao Scott correction for complex samples. Cumulative incidence and incidence density were calculated. To calculate incidence density, the numerator was the number of cases of cognitive decline during the period and the denominator was the number of person-years assessed during the period. The observation periods were computed as follows: (1) for those that died, the time transpired between the interview date in 2006 and the date of death; (2) for persons that developed cognitive decline, half the time between the interview date in 2006 and 2010; (3) for elderly that did not develop decline, the time between the interview date in 2006 and 2010.

Variables with p < 0.20 in the bivariate analysis were added stepwise to the Poisson model, according to the following blocks: socio-demographic, health status/lifestyle, and functionality. Variables with p < 0.05 or that adjusted the incidence ratio by at least 10% were kept in the final Poisson multivariate model. Multivariate analysis was controlled for the effects of socio-demographic, health status, lifestyle, and functionality variables. The model's results were presented as incidence ratios and their respective 95% confidence intervals (95%CI). Probability curves for cognitive decline were constructed from the results obtained in the logistic regression model.

The analysis used Stata 11.0 (Stata Corp., College Stations, USA), with the svy command, which allows considering the sample's complex structure, including the assignment of sampling weights.

Results

The final sample consisted of 819 elderly, representing 676,722 elderly from the city of São Paulo. Incidence of cognitive decline was 7.9% in a mean period of 4 years follow-up. Incidence density was 16/1,000 person-years (95%CI: 12.7-20.5). Incidence in men was 15.3/1,000 person-years (95%CI: 10.1-24.1) and in women 16.5/1,000 person-years (95%CI: 12.5-22.2).

Table 1 compares the population included (1,152 persons without cognitive decline) and losses to follow-up in this study (death, institutionalization, change of address, refusal, and incomplete data for the study target covariates). The excluded showed higher prevalence of individuals with worse health status and functionality. Among the excluded, there were proportionally more men (49%) than in the sample (36.9%) and higher prevalence of disabling diseases such as cerebrovascular diseases (9%), COPD (15.7%), and cancer (7.4%). There was a higher prevalence of smokers (17.9%) and lower mean number of AADL performed (3.5). Impaired mobility also showed a statistically significant difference between the included and excluded, with the latter showing a higher prevalence of impaired mobility (18.4%).

Table 2 shows the study population's characteristics in the association between the independent variables and incidence of cognitive decline. The majority of the elderly were females, and approximately 40% had 0-3 years of schooling. As for health status, the majority had two or more diseases, and self-rated overall health was bad. Mean AADL was 4.7 (95%CI: 4.5-4.9).

Bivariate analysis showed that two socio-demographic variables (schooling and age), two related to health and lifestyle (alcohol consumption and self-rated health), and two related to functionality in ADL (difficulties with ADL and number of AADL) were significantly related to cognitive decline. Elderly with cognitive decline in 2010 had presented significantly low mean AADL in 2006 (3.3; 95%CI: 2.8-3.8; p < 0.001), compared to those that did not develop decline (5.1; 95%CI: 4.8-5.4).

Table 3 shows the final Poisson regression model for variables associated with incidence of cognitive decline in 2010. More schooling reduced the risk of decline by 62% and 89%, for elders with 4-7 and ≥ 8 years of schooling, respectively. Age 75 years or older increased the incidence of decline by 3.29 times. Meanwhile, risk of cognitive decline was 2.15 times higher in elderly with difficulties in ADL. The higher the number of AADL performed, the lower the risk of cognitive decline. Alcohol abuse increased the risk of cognitive decline by 2.44 times.

Figure 1 shows the probabilities of cognitive decline adjusted by the participants' AADL and schooling. Elders with less schooling showed a higher likelihood of decline when compared to individuals with ≥ 8 years of school. Performance of ≥ 8 activities rendered the likelihood of decline insignificant between the two groups.

Discussion

The current study's results show that performance of advanced activities of daily living was a protective factor against the development of cognitive decline, independently of socioeconomic status, overall health status, lifestyle, and functional incapacity in activities of daily living.

The difference between methodologies used in the studies hinders the comparison of results as to measuring the effects of AADL. Unlike BADL and IADL, which are relatively stable between populations, AADL are culturally dependent and gender-specific, thus making their assessment difficult ⁹9. Dias EG, Duarte YAO, Almeida MHM, Lebrão ML. Caracterização das atividades avançadas de vida diária (AAVDS): um estudo de revisão. Rev Ter Ocup 2011; 22:45-51.,¹⁰10. Reuben DB, Solomon DH. Assessment in geriatrics: of caveats and names. J Am Geriatr Soc 1989; 37:570-2.. Studies highlight the need for diverse stimuli and high levels of involvement in activities ²⁷27. Avlund K, Legarth KH. Leisure activities among 70-year-old men and women. Scand J Occup Ther 1994; 1:35-44.,²⁸28. Menec H. The relation between everyday activities and successful aging: a 6-year longitudinal study. J Geront B Soc Sci 2003; 58:74-82.. In the current study, the separate analysis of each AADL did not prove significant in the multivariate model. However, when assessing the score resulting from the number of AADL, the effects proved to be enhanced.

The findings show not only that the number of AADL performed is important for maintaining cognitive capacity, but that fewer AADL performed are a predictor of cognitive decline. There was a 22% absolute difference in the adjusted probability of decline between elderly that did not perform AADL and those that performed 12 activities (data not shown). The findings thus provide evidence that these activities can be used as an ancillary instrument in the assessment of cognitive function in the elderly ¹³13. De Vriendt P, Gorus E, Cornelis E, Velghe A, Petrovic M, Mets T. The advanced activities of daily living: a tool allowing the evaluation of subtle functional decline in mild cognitive impairment. J Nutr Health Aging 2013; 17:64-71.. There is evidence that patients with mild cognitive decline display lower scores on the MMES and on performance of complex activities, especially tasks that involve memory or complex reasoning ¹⁴14. Perneczky R, Pohl C, Sorg C, Hartmann J, Komossa K, Alexopoulos P, et al. Complex activities of daily living in mild cognitive impairment: conceptual and diagnostic issues. Age Ageing 2006; 35:240-5.. Corroborating our results, Sörman et al. ²⁹29. Sörman DE, Sundström A, Rönnlund M, Adolfsson R, Nilsson LG. Leisure activity in old age and risk of dementia: a 15-year prospective study. J Gerontol B Psychol Sci Soc Sci 2014; 69:493-501. found that risk of dementia at 15 years was lower among elderly that performed more activities at baseline. However, this association was not maintained when the authors analyzed the effect of these activities in show intervals. The association was only observed between baseline and the first 5-year follow-ups. The authors thus highlight that the protective effect of these activities may be small when they begin at more advanced ages. On the other hand, the same authors do not rule out the possibility of reverse causality, since limited involvement in activities could be due to preexisting decline.

There is no consensus concerning the mechanism by which AADL protect against cognitive decline ³⁰30. Wang HX, Winblad B, Fratiglioni L. Late-life engagement in social and leisure activitiesis associated with a decreased risk of dementia: a longitudinal study from the Kungsholmen project. Am J Epidemiol 2002; 155:1081-7.,³¹31. Glei DA, Landau DA, Goldman N, Chuang Y, Rodríguez G, Weinstein M. Participating in social activities helps preserve cognitive function: an analysis of a longitudinal, population-based study of the elderly. Int J Epidemiol 2005; 34:864-71.,³²32. Argimon IIL, Stein LM. Habilidades cognitivas em indivíduos muito idosos: um estudo longitudinal. Cad Saúde Pública 2005; 21:64-72.,³³33. Maier H. Klumb PL. Social participation and survival at older ages: is the effect driven by activity content or context? Eur J Ageing 2005; 2:31-9.. The literature suggests that patterns of activity and related neural networks that are established in early life may be more important for maintaining cognitive health in old age, in the sense of minimizing the effects of decreasing velocity of cognitive processing in aging ³⁰30. Wang HX, Winblad B, Fratiglioni L. Late-life engagement in social and leisure activitiesis associated with a decreased risk of dementia: a longitudinal study from the Kungsholmen project. Am J Epidemiol 2002; 155:1081-7.,³⁴34. Salthouse TA. The processing-speed theory of adult age differences in cognition. Psychol Rev 1996; 103:403-28.. Exposure to complex environments with stimulating brain experiences throughout life, related to socio-demographic and functionality variables, such as more schooling and more complex work activities and leisure-time activities, are believed to promote neuronal growth and favor neuroplasticity. These factors contribute to the construction, formation, and maintenance of better levels of cognitive reserve, fostering greater resistance to brain damage ³⁵35. Fratiglioni L, Paillard-Borg S, Winblad B. An active and socially integrated lifestyle in late life might protect against dementia. Lancet Neurol 2004; 3:343-53.,³⁶36. Stern C, Munn Z. Cognitive leisure activities and their role in preventing dementia: a systematic review. Int J Evid Based Healthc 2010; 8:2-17.,³⁷37. Valenzuela MJ, Sachdev P. Brain reserve and dementia: a systematic review. Psychol Med 2006; 36:441-54.,³⁸38. Liberati G, Raffone A, Olivetti BM. Cognitive reserve and its implications for rehabilitation and Alzheimer's disease. Cogn Process 2012; 13:1-12. and potentially postponing the emergence of cognitive deficits ³⁹39. Stern Y. What is cognitive reserve? Theory and research application of the reserve concept. J Int Neuropsychol Soc 2002; 8:448-60.,⁴⁰40. Barulli D, Stern Y. Efficiency, capacity, compensation, maintenance, plasticity: emerging concepts in cognitive reserve. Trends Cogn Sci 2013; 17: 502-9..

In addition, AADL involve volitional activities, influenced by the sociocultural context and motivational factors, with pleasurable relations in the performance of activities, transposing the meanings of independent community living¹⁰10. Reuben DB, Solomon DH. Assessment in geriatrics: of caveats and names. J Am Geriatr Soc 1989; 37:570-2.,¹¹11. Reuben DB, Laliberte L, Hiris J, Mor V. A hierarchical exercise scale to measure function at the advanced activities of daily living (AADL) level. J Am Geriatr Soc 1990; 38:855-61.,¹²12. De Vriendt P, Gorus E, Cornelis E, Velghe A, Petrovic M, Mets T. The process of decline in advanced activities of daily living: a qualitative explorative study in mild cognitive impairment. Int Psychogeriatr 2012; 24:974-86.,²⁹29. Sörman DE, Sundström A, Rönnlund M, Adolfsson R, Nilsson LG. Leisure activity in old age and risk of dementia: a 15-year prospective study. J Gerontol B Psychol Sci Soc Sci 2014; 69:493-501.. Characteristics related to AADL allow visualizing individuals' social roles and interests, in addition to the integrity of important physical and social functions that indicate more complex functional levels.

Longitudinal studies report on the importance of maintaining activities over time among the elderly, especially preserving individual preferences. The maintenance of work-related and leisure-time activities in old age has been associated with better cognitive functioning in European elderly ⁴¹41. Adam S, Bonsang E, Grotz C, Perelman S. Occupational activity and cognitive reserve: implications in terms of prevention of cognitive aging and Alzheimer's disease. Clin Interv Aging 2013; 8:377-90.. In addition, a population-based study with French elderly found that postponing the age of retirement was associated with a significant reduction in the risk of Alzheimer's disease ⁴²42. Delaying retirement may reduce Alzheimer's risk. Mayo Clin Health Lett 2014; 32:4..

The emergence of functional incapacities appears to be the principal factor in decreasing and/or abandoning activities ¹⁶16. Di Rienzo VD. Participação em atividades e funcionamento cognitivo: estudo de coorte com idosos residentes em área de baixa renda no Município de São Paulo [Tese de Doutorado]. São Paulo: Faculdade de Medicina, Universidade de São Paulo; 2009.,⁴³43. Agahi N, Ahacic K, Parker MG. Continuity of leisure participation from middle age to old age. J Gerontol B Psychol Sci Soc Sci 2006; 61:S340-6.,⁴⁴44. Rosso AL, Eaton CB, Wallace R, Gold R, Stefanick ML, Ockene JK, et al. Geriatric syndromes and incident disability in older women: results from the women's health initiative observational study. J Am Geriatr Soc 2013; 61:371-9.. Impairment of AADL, observed as alterations in quality of performance or a decrease in the number of activities usually performed throughout life could be related to the beginning of physical or cognitive functional decline, depressive symptoms, contextual barriers, weak support network, and/or more significant impairments related to chronic non-communicable diseases and conditions (NCDs) ¹⁶16. Di Rienzo VD. Participação em atividades e funcionamento cognitivo: estudo de coorte com idosos residentes em área de baixa renda no Município de São Paulo [Tese de Doutorado]. São Paulo: Faculdade de Medicina, Universidade de São Paulo; 2009.,⁴³43. Agahi N, Ahacic K, Parker MG. Continuity of leisure participation from middle age to old age. J Gerontol B Psychol Sci Soc Sci 2006; 61:S340-6.,⁴⁴44. Rosso AL, Eaton CB, Wallace R, Gold R, Stefanick ML, Ockene JK, et al. Geriatric syndromes and incident disability in older women: results from the women's health initiative observational study. J Am Geriatr Soc 2013; 61:371-9..

Productive and leisure-time social activities (AADL) favor the full development of potentialities in elderly, with exchange of experiences, support, and affection among members of the social network. There is a substitution of roles and persons, with a view towards building a stable network that fosters belonging, but simultaneously allows new actors to enter and leave, thus becoming more flexible ⁴⁵45. Mendes MRSSB, Gusmão JL, Faro ACM, Leite RCBO. A situação social do idoso no Brasil: uma breve consideração. Acta Paul Enferm 2005; 18: 422-6..

The cognitive reserve theory appears to provide the main explanation for the effects of performing complex activities throughout life and for lower odds of developing cognitive decline. Patterns of activity and related neural networks established in early life may be more important for maintaining cognitive health in old age ²⁹29. Sörman DE, Sundström A, Rönnlund M, Adolfsson R, Nilsson LG. Leisure activity in old age and risk of dementia: a 15-year prospective study. J Gerontol B Psychol Sci Soc Sci 2014; 69:493-501.. Evidence shows that more schooling, participation in complex work activities, and leisure-time activities that involve cognitive processes are associated with building and maintaining cognitive reserve ²2. Valenzuela MJ, Sachdev P. Assessment of complex mental activity across the lifespan: development of the Lifetime of Experiences Questionnaire (LEQ). Psychol Med 2007, 37:1015-25.,³⁰30. Wang HX, Winblad B, Fratiglioni L. Late-life engagement in social and leisure activitiesis associated with a decreased risk of dementia: a longitudinal study from the Kungsholmen project. Am J Epidemiol 2002; 155:1081-7.,³⁵35. Fratiglioni L, Paillard-Borg S, Winblad B. An active and socially integrated lifestyle in late life might protect against dementia. Lancet Neurol 2004; 3:343-53.,³⁶36. Stern C, Munn Z. Cognitive leisure activities and their role in preventing dementia: a systematic review. Int J Evid Based Healthc 2010; 8:2-17.,⁴⁶46. Fratiglioni L, Qiu C. Prevention of common neurodegenerative disorders in the elderly. Exp Gerontol 2009; 44:46-50.,⁴⁷47. Verghese J, Lipton RB, Katz MJ, Hall CB, Derby CA, Kuslansky G, et al. Leisure activities and the risk of dementia in the elderly. N Engl J Med 2003; 348:2508-16..

As for socio-demographic factors, corroborating other studies ⁶6. Yaffe K, Fiocco AJ, Lindquist K, Vittinghoff E, Simonsick EM, Newman AB. Predictors of maintaining cognitive function in older adults: the Health ABC Study. Neurology 2009; 72:2029-35.,²⁰20. Castro-Costa E, Dewey ME, Uchôa E, Firmo JO, Lima-Costa MF, Stewart R. Trajectories of cognitive decline over 10 years in Brazilian elderly population: the Bambuí Cohort Study of Aging. Cad Saúde Pública 2011; 27 Suppl 3:S345-50.,³²32. Argimon IIL, Stein LM. Habilidades cognitivas em indivíduos muito idosos: um estudo longitudinal. Cad Saúde Pública 2005; 21:64-72.,⁴⁰40. Barulli D, Stern Y. Efficiency, capacity, compensation, maintenance, plasticity: emerging concepts in cognitive reserve. Trends Cogn Sci 2013; 17: 502-9.,⁴⁷47. Verghese J, Lipton RB, Katz MJ, Hall CB, Derby CA, Kuslansky G, et al. Leisure activities and the risk of dementia in the elderly. N Engl J Med 2003; 348:2508-16.,⁴⁸48. Akbaraly TN, Portet F, Fustinoni S, Dartigues JF, Artero S, Rouaud O, et al. Leisure activities and the risk of dementia in the elderly: results from the Three-City Study. Neurology 2009; 73:854-61.,⁴⁹49. Jonaitis E, La Rue A, Mueller KD, Koscik RL, Hermann B, Sager MA. Cognitive activities and cognitive performance in middle-aged adults at risk for Alzheimer's disease. Psychol Aging 2013; 28: 1004-14., we found that more schooling significantly reduced the odds of cognitive decline.

Importantly, the odds of decline estimated as the number of AADL and stratified by schooling showed that even for elderly with little schooling (0-3 years), performing 8 or more AADL reduced the probability of decline to levels close to those found for individuals with ≥ 8 years of school (Figure 1). This information pertains particularly to the supply of strategies to promote physical and cognitive health among the elderly in developing countries, which have low mean levels of schooling.

According to the literature ⁶6. Yaffe K, Fiocco AJ, Lindquist K, Vittinghoff E, Simonsick EM, Newman AB. Predictors of maintaining cognitive function in older adults: the Health ABC Study. Neurology 2009; 72:2029-35.,⁴⁶46. Fratiglioni L, Qiu C. Prevention of common neurodegenerative disorders in the elderly. Exp Gerontol 2009; 44:46-50., age is the factor most closely associated with cognitive decline, due to the accumulation of disease processes and exposure to other risk factors over the course of life and with aging ⁵⁰50. Foubert-Samier A, Catheline G, Amieva H, Dilharreguy B, Helmer C, Allard M, et al. Education, occupation, leisure activities, and brain reserve: a population-based study. Neurobiol Aging 2012; 33:423.e15-25.. Data from the literature show that elders begin reducing their advanced activities of daily living at around 75 years of age, when functional incapacities emerge, especially in performing activities away from home. An Australian cross-sectional study found that elders 75 years and older spent more time alone and were less involved in work-related activities and use of transportation. Older persons presented more serious functional losses and abandonment of occupational roles ⁵¹51. McKenna K, Broome K, Liddle J. What older people do: time use and exploring the link between role participation and life satisfaction in people aged 65 years and over. Aust Occup Ther J 2007; 54:273-84..

The study's strengths feature the longitudinal design of the SABE study, with the use of a complex representative sample of the elderly population in the city of São Paulo and systematic collection of different factors known to be associated with cognitive decline, thus aiding the identification of the role of AADL in the outcome, independently of these characteristics. The study's limitations are related to the lack of a gold standard to confirm the results obtained with the modified version of the MMSE. Another limitation was the lack of use of a validated questionnaire for assessing AADL and lack of information on the initial period of involvement in these activities over the course of life. In addition, as reported by other longitudinal studies ¹⁹19. Wilkosz PA, Seltman HJ, Devlin B, Weamer EA, Lopez OL, DeKosky ST, et al. Trajectories of cognitive decline in Alzheimer's disease. Int Psychogeriatr 2010; 22:281-90., one cannot rule out some reverse causality effect, since a low number of AADL at baseline could be due to preexisting mild decline, undetected by cognitive screening tests. These issues emphasize the need for validation of an instrument to assess AADL and on-going follow-ups, aimed at assessing the effect's stability over time.

In conclusion, practicing more advanced activities of daily living can be a protective factor against cognitive decline in non-institutionalized elderly. The effects of AADL on incidence of cognitive decline were maintained even after adjusting for covariates commonly reported in the scientific literature on cognitive decline.

Acknowledgments

The authors wish to thank the research team, interviewers, and elders for their essential contribution to the SABE study.

References

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