Social Activity, Cognitive Decline and Dementia Risk: A 20-year Prospective Cohort Study

Riccardo E. Marioni; Cecile Proust-Lima; Helene Amieva; Carol Brayne; Fiona E. Matthews; Jean-Francois Dartigues; Helene Jacqmin-Gadda

Disclosures

BMC Public Health. 2015;15(1089) 

In This Article

Background

Increased social engagement and cognitive lifestyle activities have been associated with a decreased risk of cognitive decline and dementia.[1–4] Such markers are particularly promising from a public health perspective due to their modifiable nature.[5] However, due to the heterogeneity in measuring both social activity and cognitive ability, and with methodological challenges of analysing longitudinal population-based data, there is no consensus over which measures of social activity are the most important, which cognitive domains they affect (e.g., memory, processing, general ability), and if they have differential effects depending on the stage of decline (e.g., dementia[6] or mild cognitive impairment[7]). For example, a study by Seeman et al.[8] found frequent contact with family and friends and positive social support to be associated with better performance on tests of episodic memory and executive function. A 20-year follow-up study of Swedish data found mid-life political and mental activities, but not physical, social, cultural, or organizational activities to be associated with cognitive ability in later life.[9] Another study by Green et al.[10] found cross-sectional but not longitudinal associations between social networks and cognition.

One potential issue with models of social activity and cognitive decline is the possibility of reverse causation. People who have begun to decline and are entering a dementia phase at the start of a study may already have experienced a reduction in their social contacts.[11,12] Further variation is introduced upon considering analytical issues common to longitudinal analyses of cognitive data. These include measurement error of cognitive function, dropout due to death and dementia, practice effects, and non-Gaussian distribution of cognitive test scores. Recently, we described two modelling approaches that can accommodate some of these issues – multi-state models and joint latent class mixed models.[13]

Here we examine four markers of lifestyle activity and self-perception of social relationships (social, physical and intellectual engagement, social network size, satisfaction with social relationships, and perceived understanding) with longitudinal cognitive change and risk of dementia. A previous analysis on the same dataset combined these factors to create an overall index that was related to cognitive ability but not decline in the six psychometric tests examined.[12] The individual facets have also been modelled against risk of dementia.[14] However, the variables have not been studied in isolation with respect to cognitive decline, and using advanced modelling methods that include multivariate repeated cognitive information and consider risk of dementia alongside decline. First, instead of considering change separately in six individual cognitive tests,[12] here we combine this multivariate information to model a single marker of general cognitive ability: the latent common factor underlying the tests. We relate the four social markers to change over time of this general cognitive ability and to the risk of dementia, which are modelled independently in the whole population. We then summarize the heterogeneity of cognitive ageing into several statistically defined homogeneous sub-populations derived from a joint latent class model that both accounts for shape of cognitive decline and dementia risk. We investigate whether lifestyle activity, self-perception of relationships are differently distributed within these homogeneous sub-populations.

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