Introduction With the fast population ageing, disability among the elderly is becoming a major public health issue. Depression is highly prevalent in this phase of life and may be associated with a significant proportion of the disability among elderly populations. We aimed to investigate the association between depressive symptoms and functional disability in older adults, independently of comorbidities and socioeconomic factors and to estimate the Population Attributable Fraction (PAF) of disability due to depressive symptoms and depression.

Methods A cross-sectional survey was carried with 2072 residents aged 65 years or over living in a low-income area of São Paulo, Brazil. ICD-10 depression and depressive symptoms were assessed with the Geriatric Mental State and the Neuropsychiatric Inventory. The assessment of disability was made using the WHO Disability Assessment Schedule Instrument (WHO-DASII). The 90^th percentile of WHO-DAS scores was considered as high disability.

Results The prevalence of depression and depressive symptoms were 4.8% and 21.4%, respectively. Depression (OR 8.0; 95% CI 4.2 to 14.3) and depressive symptoms (OR 2.7; 95% CI 1.7 to 4.2) were strongly associated with high disability, even after adjustment for all demographic and socioeconomic conditions and physical morbidities. Depression had a PAF of 15% (95% CI 10% to 19%), whereas depressive symptoms had a PAF of 17% (95% CI 9% to 24%).

Conclusions Depression and depressive symptoms were the morbidities that contributed most to the framework of disability in the elderly. Effective management of depressive states in the elderly, delivered at the primary care level, may reduce the total population disability.