P4‐313: Age of dementia onset delayed by bilingualism, but advanced by stroke

Abstract

High educational status and complex mental activities are thought to delay onset of dementia, while vascular risk factors increase dementia risk. It is still unclear how these different biological and lifestyle factors interact to impact dementia risk. India is characterised by heterogeneity in educational status, widespread bilingualism and high cardiovascular risk burden, providing a unique opportunity to study lifestyle and biological factors that protect or increase risk of dementia. We aimed to investigate the association between educational status, bilingualism and cardiovascular risk factors on age of dementia onset, subtypes and severity. 347 consecutive dementia patients in a hospital based registry (Alzheimer's disease (AD)-133, Vascular dementia (VaD)-88, Frontotemporal dementia (FTD)-65, Lewy Body Dementia (DLB)-31, Mixed Dementia-30) were evaluated for presence of vascular risk factors (diabetes, hypertension, smoking, alcoholism, cardiac disease and stroke), bilingualism and years of education. 59% of subjects were bilingual and 16% were illiterate. Effect of these factors on age of dementia onset, subtype, and severity were studied. Independent effects of education, vascular risk factors and bilingualism on age of onset of dementia were analysed by linear regression analysis. Bilingualism was associated with a 3.9 year delay in onset of dementia compared with monolingualism. Bilingualism was related to a later age of onset of AD and FTD, but not VaD, mixed dementia and DLB. Higher educational status was found to relate to a later onset. Among cardiovascular risk factors, stroke was strongly associated with younger age of onset of dementia. Effect of other vascular risk factors on age of onset was not significant. Severity of dementia was associated with low educational status and monolingualism. Linear regression analysis revealed that bilingualism (p = 0.002) and stroke (p = 0.008) and not educational status had an independent effect on age of onset. In this large series of dementia patients, bilingualism more than educational status was found to independently delay age of onset of dementia, especially AD and FTD. Stroke was strongly associated with earlier age of onset. The study provides insights into interaction between biological and lifestyle protective and risk factors in impacting dementia burden.