Lifestyle factors, cognitive reserve, and cognitive function: results from the Cognitive Function and Ageing Study Wales, a population-based cohort

Abstract

BackgroundA wide range of lifestyle factors has been related to cognitive decline and dementia but the mechanisms have not been investigated completely. Cognitive reserve, the ability to optimise or maximise cognitive performance by drawing on a range of brain networks and cognitive strategies, accumulates throughout the life course and might have a mediating role in the pathway between lifestyle factors and cognitive function in later life. The aim of this study was to investigate the potential mediating effect of cognitive reserve on the association between cognitive function and lifestyle factors in a large cohort of older people in Wales. MethodsThis analysis was based on 2315 participants in the Cognitive Function and Ageing Study Wales, a longitudinal population-based study of people aged 65 and over in two areas in Wales (Gwynedd and Anglesey, Neath and Port Talbot), excluding people living in institutions or having dementia, depression, or cognitive impairment at baseline. Lifestyle factors included physical activity, smoking (never, former, current), frequency of alcohol consumption (from abstinent to almost every day), dietary pattern (intake of fruit, vegetables, fish, and wholemeal bread), and cognitive and social activity. Linear regression modelling was used to investigate the associations between lifestyle factors, cognitive reserve (measured by education and occupational complexity), and cognitive function and to estimate the indirect effects through cognitive reserve with bootstrapping CIs. All measures were standardised to provide comparable coefficients. FindingsAll lifestyle factors apart from smoking (no association) were positively associated with cognitive function and explained 20% of variation across individuals after adjusting for age, sex, and chronic conditions. Cognitive reserve contributed 22% of the indirect effect (standardised coefficient of total indirect effect 0·08, 95% CI 0·07–0·11) on the overall association between cognitive function and four lifestyle factors (standardised coefficient of total effect for four lifestyle factors 0·39, 0·32–0·46). The strongest indirect effect was seen in dietary pattern (standardised coefficient 0·04, 0·03–0·05). InterpretationCognitive reserve appears to be an important mediator in the pathway between lifestyle and cognitive function. This special mechanism for brain health in older age could inform the development of dementia prevention and risk reduction strategies. FundingEconomic and Social Research Council.