Modifiable lifestyle factors and cognitive reserve: A systematic review of current evidence

Abstract

This systematic review aims to summarize cognitive reserve (CR) evaluation approaches and to examine the role of seven selected modifiable lifestyle factors (diet, smoking, alcohol consumption, physical activity, cognitive leisure activity, sleep, and meditation) in mitigating the impacts of age- or disease-related brain changes on cognition. Eighteen population-based English empirical studies were included. We summarize the study designs and identify three CR models that were broadly used in these studies, including a residual model assessing lifestyle factors in relation to unexplained variance in cognition after accounting for brain markers, a moderation model testing whether lifestyle factors moderate the relationship between brain status and cognition, and a controlling model examining the associations between lifestyle factors and cognition when controlling for brain measures. We also present the findings for the impact of each lifestyle factor. No studies examined diet, sleep, or meditation, and only two studies focused on smoking and alcohol consumption each. Overall, the studies suggest lifestyle activity factors (physical and cognitive leisure activities) may contribute to CR and attenuate the damaging impact of brain changes on cognition. Standardized measurements of lifestyle factors and CR are needed, and mechanisms underlying CR need to be further addressed as well.

Keywords: Brain markers; Cognition; Cognitive reserve; Modifiable lifestyle factors.

Figure 1.

PRISMA diagram.

Figure 2.. Cognitive reserve mechanisms for the role of lifestyle factors in the associations between brain markers and cognition.

Abbreviations: LS: lifestyle factors; CR: cognitive reserve. Note: Model 1-Residual: analysing the associations between lifestyle factors and CR residuals, which are quantified as the unexplained variance in cognition after taking demographic and brain markers of cognition into account. Model 2-Moderation: testing whether lifestyle factors moderate the association between brain status and cognition by examining the interaction between lifestyle factors and brain markers on cognition. Model 3-Controlling model: conducting multivariable regressions with lifestyle factors as the predictors and cognition as the outcomes while accounting for brain markers, or regressing lifestyle factors with brain markers, controlling for cognition.