Abstract
BackgroundIdentifying modifiable lifestyle correlates of cognitive decline and risk of dementia is complex, particularly as few population-based longitudinal studies jointly model these interlinked processes. Recent methodological developments allow us to examine statistically defined sub-populations with separate cognitive trajectories and dementia risks.MethodsEngagement in social, physical, or intellectual pursuits, social network size, self-perception of feeling well understood, and degree of satisfaction with social relationships were assessed in 2854 participants from the Paquid cohort (mean baseline age 77 years) and related to incident dementia and cognitive change over 20-years of follow-up. Multivariate repeated cognitive information was exploited by defining the global cognitive functioning as the latent common factor underlying the tests. In addition, three latent homogeneous sub-populations of cognitive change and dementia were identified and contrasted according to social environment variables.ResultsIn the whole population, we found associations between increased engagement in social, physical, or intellectual pursuits and increased cognitive ability (but not decline) and decreased risk of incident dementia, and between feeling understood and slower cognitive decline. There was evidence for three sub-populations of cognitive aging: fast, medium, and no cognitive decline. The social-environment measures at baseline did not help explain the heterogeneity of cognitive decline and incident dementia diagnosis between these sub-populations.ConclusionsWe observed a complex series of relationships between social-environment variables and cognitive decline and dementia. In the whole population, factors such as increased engagement in social, physical, or intellectual pursuits were related to a decreased risk of dementia. However, in a sub-population analysis, the social-environment variables were not linked to the heterogeneous patterns of cognitive decline and dementia risk that defined the sub-groups.Electronic supplementary materialThe online version of this article (doi:10.1186/s12889-015-2426-6) contains supplementary material, which is available to authorized users.
Highlights
Identifying modifiable lifestyle correlates of cognitive decline and risk of dementia is complex, as few population-based longitudinal studies jointly model these interlinked processes
Increased social engagement and cognitive lifestyle activities have been associated with a decreased risk of cognitive decline and dementia [1,2,3,4]
We 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
Summary
Identifying modifiable lifestyle correlates of cognitive decline and risk of dementia is complex, as few population-based longitudinal studies jointly model these interlinked processes. Increased social engagement and cognitive lifestyle activities have been associated with a decreased risk of cognitive decline and dementia [1,2,3,4]. Such markers are promising from a public health perspective due to their modifiable nature [5]. 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. We described two modelling approaches that can accommodate some of these issues – multi-state models and joint latent class mixed models [13]
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