Potentially modifiable lifestyle factors, cognitive reserve, and cognitive function in later life: A cross-sectional study

Abstract

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.

Abstract

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.