OBJECTIVE: Dementia is a leading cause of disability and dependence among older adults worldwide, with its prevalence increasing due to rising life expectancy. Evidence suggests that dementia may be preventable. In 2024, the Lancet Commission identified 14 modifiable risk factors for dementia. Investigating their impact in the oldest-old is essential to inform prevention strategies. Within this context, we sought to evaluate the association between modifiable risk factors identified by the 2024 Lancet Commission and the incidence of dementia in a cohort of cognitively healthy oldest-old Brazilians. We hypothesized that the influence of these factors may differ in very late life compared with midlife, particularly in a socioeconomically diverse Latin American population.
METHODS: This longitudinal study followed 273 participants aged 80 years and older (mean age 85.2 ± 4.48 years) between 2010 and 2020. The cohort originated from the Department of Geriatrics and Gerontology at the Escola Paulista de Medicina –Universidade Federal de São Paulo. Competing risks models (Fine and Gray) were applied to account for death and dementia. The primary outcome was incident dementia, defined as functional decline related to cognitive impairment. Kaplan-Meier curves were initially explored, followed by competing risks models. Twelve factors were evaluated: educational attainment, hypertension, hearing impairment, smoking, body mass index, depression, physical activity, diabetes, social contact, alcohol consumption, dyslipidemia, and traumatic brain injury. Analyses were conducted using RStudio (survival, survminer, cmprsk), with significance set at 5%. Participants lost to follow-up were censored, and deaths contributed data up to the last assessment.
RESULTS: During follow-up, 23.4% of participants developed dementia and 29.3% died without dementia. Low BMI (<18.5 kg/m2) was the only factor significantly associated with increased dementia risk (HR = 5.03; p = 0.02).
CONCLUSIONS: These findings highlight the relevance of nutritional status in the assessment of dementia risk among the oldest-old. Individuals aged 80 years and older may remain cognitively preserved for extended periods, underscoring the need for further research to better define risk and protective factors in this population.
Keywords: dementia, cognition, aged 80 and over, risk factors, survival analysis.