Search

Background Potentially modifiable lifestyle factors may influence cognitive health in later life and offer potential to reduce the risk of cognitive decline and dementia. The concept of cognitive reserve has been proposed as a mechanism to explain individual differences in rates of cognitive decline, but its potential role as a mediating pathway has seldom been explored using data from large epidemiological studies. We explored the mediating effect of cognitive reserve on the cross-sectional association between lifestyle factors and cognitive function in later life using data from a population-based cohort of healthy older people. Methods and findings We analysed data from 2,315 cognitively healthy participants aged 65 y and over in the Cognitive Function and Ageing Study Wales (CFAS-Wales) cohort collected in 2011–2013. Linear regression modelling was used to investigate the overall associations between five lifestyle factors—cognitive and social activity, physical activity, diet, alcohol consumption, and smoking—and cognition, adjusting for demographic factors and chronic conditions. Mediation analysis tested for indirect effects of the lifestyle factors on cognition via cognitive reserve. After controlling for age, gender, and the presence of chronic conditions, cognitive and social activity, physical activity, healthy diet, and light-to-moderate alcohol consumption were positively associated with cognitive function, together accounting for 20% (95% CI 17%–23%) of variance in cognitive test scores. Cognitive reserve was an important mediator of this association, with indirect effects via cognitive reserve contributing 21% (95% CI 15%–27%) of the overall effect on cognition. The main limitations of the study derive from the cross-sectional nature of the data and the challenges of accurately measuring the latent construct of cognitive reserve. Conclusions Cross-sectional associations support the view that enhancing cognitive reserve may benefit cognition, and maintenance of cognitive health may be supported by a healthy and active lifestyle, in later life., In a cross-sectional study, Linda Clare and colleagues investigate whether healthy lifestyle choices are associated with better cognitive function later in life., Author summary Why was this study done? Individual differences in lifestyle factors such as physical activity or diet may be related to differences in mental fitness in later life. Differences in the extent to which mental fitness declines in later life are thought to arise because some people’s earlier experiences (for example, staying on for further education or playing a leadership role in a job) make their brains more resilient to changes resulting from age or illness—they have higher “cognitive reserve.” We wanted to find out whether the concept of cognitive reserve explains how lifestyle influences mental fitness. What did the researchers do and find? We used data from 2,315 mentally fit participants aged over 65 y who took part in the first wave of interviews for the Cognitive Function and Ageing Study Wales (CFAS-Wales). Our statistical analyses examined whether a healthy lifestyle (a healthy diet, more physical activity, more social and mentally stimulating activity, moderate alcohol consumption, and refraining from smoking), adjusted to take account of age, gender, and whether people had long-term health conditions, was associated with performance on a test of mental ability. When we found an association, we then investigated whether this association was explained by the level of cognitive reserve. We found that people with a healthier lifestyle had better mental fitness, and this was partly accounted for by their level of cognitive reserve. What do these findings mean? These results highlight the importance of policies and interventions that encourage older people to make changes in their diet, exercise more, and engage in more socially oriented and mentally stimulating activities. Earlier life experiences build cognitive reserve, which helps to maintain mental fitness in later life, so access to education and opportunities to develop skills in the workplace are important in developing this resilience. The main limitation of this study is that we used data collected at only one time point, which means that we cannot draw any conclusions about causes or trajectories—we can only say for sure that lifestyle and mental fitness are related.

Age can affect memory performance. This statement is so often heard that it has become almost a truism. When research surrounding memory inhibition – the ability to ignore irrelevant material to aid in the retrieval of a target memory – is examined specifically, a more mixed picture of findings emerges. Whilst some previous work has found evidence of an age-related deficit, other research has rather found intact memory inhibition in older adults. Less often discussed, too, are the effects of individual differences on memory inhibition in addition to age, including differences in metacognitive strategy, working memory capacity, stress and mood. The present thesis set out primarily to investigate the effects of age on memory inhibition chiefly using cognitive experimental paradigms, and also to investigate potential individual differences in this ability which exist across the lifespan. The findings of the present thesis showed that age alone was not related to a deficit in memory inhibition, - young and older adults rather showed equivalent levels of inhibitory forgetting on two different paradigms, when methodological measures were put in place to control for alternative, interference-based explanations (Study 1). These findings also could not be explained by differences in metacognitive, covert-cuing strategies (Study 2). Instead, age-related inhibitory deficits were qualified by differences in working memory capacity (Study 3a & b). In combination, older age and low working memory capacity were related to impaired memory inhibition, whereas young age or high working memory capacity were not. Finally, natural variations in stress and mood over time were found to be related to significant differences in working memory capacity, but not memory inhibition (Study 4). This suggests that these important cognitive abilities may be capable of changing even over relatively short time periods, and thus they may also potentially be improved, - a proposal which is considered in the General Discussion.