A systematic review and meta-analysis of structural magnetic resonance imaging studies investigating cognitive and social activity levels in older adults

Abstract

Population aging has prompted considerable interest in identifying modifiable factors that may help protect the brain and its functions. Collectively, epidemiological studies show that leisure activities with high mental and social demands are linked with better cognition in old age. The extent to which socio-intellectual activities relate to the brain's structure is, however, not yet fully understood. This systematic review and meta-analysis summarizes magnetic resonance imaging studies that have investigated whether cognitive and social activities correlate with measures of gray and white matter volume, white matter microstructure and white matter lesions. Across eighteen included studies (total n = 8429), activity levels were associated with whole-brain white matter volume, white matter lesions and regional gray matter volume, although effect sizes were small. No associations were found for global gray matter volume and the evidence concerning white matter microstructure was inconclusive. While the causality of the reviewed associations needs to be established, our findings implicate socio-intellectual activity levels as promising targets for interventions aimed at promoting healthy brain aging.

Keywords: Aging; Brain; Cognitive activity; Gray matter; Magnetic resonance imaging; Region-of-interest; Social activity; Voxel-based morphometry; White matter.

Fig. 1

Effect sizes (correlation coefficient) for total GM volume: No significant association between CA and SA engagement and global GM volume.

Fig. 2

Effect sizes (correlation coefficient) for hippocampal volume: Higher levels of CA and SA engagement are associated with greater hippocampal volume.

Fig. 3

Effect sizes (correlation coefficient) for total WM volume: a positive relationship between CA and SA levels and whole-brain WM volume.

Fig. 4

Effect sizes (correlation coefficient) for global WM lesions: Higher CA and SA levels are related to a reduction in whole-brain WM lesion volume.

Fig. 5

Schematic diagram outlining the proposed neurobiological mechanisms that may support associations between activities and brain reserve and cognition, in old age.

Fig. 6

Schematic diagrams representing the different methods used to operationalize social (SA) and cognitive (CA) activities. a. SA and CA are treated as distinct constructs. b. SA and CA are combined into a single measure to reflect ‘socio-intellectual activities’. c. SA and CA are employed as distinct, but related constructs. d. Each activity item is examined as an independent correlate of the outcomes of interest.