Tobacco use and dementia: evidence from the 1066 dementia population-based surveys in Latin America, China and India.

OBJECTIVES: To assess the association between tobacco consumption and dementia using the same methodology in seven developing countries, testing the specific hypotheses that higher exposure to tobacco is associated with a higher prevalence of dementia, that the association is limited to smoked tobacco and is stronger for vascular dementia compared to Alzheimer's disease. METHODS: Cross-sectional surveys conducted on individuals aged 65+. A total of 15 022 residents in specified catchment areas were assessed face-to-face using a standardised protocol, which included dementia diagnosis and detailed information on past and current tobacco consumption, and on important potential confounders of this association. RESULTS: A high proportion of participants were never smokers (52% in Dominican Republic to 83% in Peru), most of those who ever used tobacco in China and India were still smoking at age 65 and above (80% and 84%, respectively). There was a positive association between history of tobacco smoke exposure (pack years up to age 50) and dementia (pooled PR = 1.003; 95%CI 1.001-1.005), Alzheimer's disease (pooled PR = 1.007; 95% CI, 1.003-1.011) and Vascular Dementia (pooled PR = 1.003; 95% CI = 1.001-1.005). These associations were attenuated but remained significant if exposure after the age of 50 was included. In India there was no association between smokeless tobacco and dementia. CONCLUSIONS: Dementia in developing countries appears to be positively associated with history of tobacco smoking but not smokeless tobacco use. Selective quitting in later life may bias estimation of associations.