AbstractBackgroundEvidences indicate that physically active older individuals maintain healthy functioning longer than do sedentary peers. Some lifestyle could impact the risk of dementia including Alzheimer’s. In spite of this, the effect of physical activity on the relationship between age and the risk of dementia is unknown. This is a two‐phase study that aims to investigate the association of physical exercise and age with the prevalence of dementia in community older adults, from Ribeirao Preto city, state of Sao Paulo, Brazil.MethodCross‐sectional study of a randomized community‐based sample of 928 elderly subjects aged 60 years or older was performed. Standardized instruments for screening dementia and a socio‐economic questionnaire were applied to the subjects at home in phase I. The dementia diagnose was made at hospital in phase II, according to DSM‐V criteria.ResultOveral Dementia was 6.0%. Alzheimer’s disease was the most frequent dementia (2.8%), followed by Vascular dementia (1.3%), and Mixed dementia (1.1%). Initial multivariate analysis showed sociodemographic factors associated to dementia. After adjusting for all the variables, multivariate analysis showed an association with age group ≥80 (OR = 6.7; p<0.001); household chores (OR = 2.7; p = 0.004); no employment (OR = 4.3; p<0.001); and stroke (OR = 4.5; p = 0.001). There was no association with gender, socioeconomic class, educational level, and alcohol use. Secondary analysis showed an inverse relationship between physical activity and age (OR = 0.4; p<0.001). After deliberately exclude age, the final model showed a significant association between higher rates of dementia and lack of physical activity (OR = 2.0; p = 0.024).ConclusionAccording to previous studies, in our sample, lack of exercise was associated with two fold higher risk of dementia, only after exclude age of the analysis. This result could be due to decreasing level of physical activity found in the oldest subjects. We suggest that relatively simple lifestyle changes such as increasing the practice of exercise could enhance cognitive performance in elderly people. Future investigations are needed to clarify the real impact of physical activity on the relationship between dementia and age.