Urban residence and higher education do not protect against cognitive decline in aging and dementia: 10-year follow-up of the Canadian Study of Health and Aging

ABSTRACT

The construct of cognitive reserve has primarily been defined in terms of a single proxy measure, education. There may, however, be alternative, potentially additive, proxy measures of cognitive reserve, such as rural or urban residence. Using a large sample of 10,263 older Canadians, ranging in age between 64 and 99 years (mean age = 75.7 years, SD = 7.1), residents of rural and urban areas were compared using the Modified Mini-Mental State (3MS) examination as a dependent variable. Within this sample, subsamples of demented and non-demented individuals were investigated. The 3MS data were analyzed using a linear mixed model with years of education and residence as proxies of cognitive reserve and time of testing (linear and quadratic) as a within-groups variable. All predictor variables in the model (i.e., gender, age, education, residence, and time of testing) had a significant impact on cognitive functioning. The results showed that, although urban residents and higher educated individuals performed better than rural residents and lower educated individuals at baseline, these performance benefits were nullified at 10-year follow-up. The disappearance of these initial performance benefits suggests that urban dwellers and higher educated individuals are not protected against age-related cognitive decline. Thus, no support was found for the cognitive reserve hypothesis.

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Acknowledgements

Core funding for Phases 1 and 2 of the Canadian Study of Health and Aging (CSHA) was provided by the Seniors’ Independence Research Program, through Health Canada’s National Health Research & Development Program (NHRDP). Funding for analysis of the caregiver component was provided by the Medical Research Council (MRC). Additional funding was provided by Pfizer Canada Inc. through the Medical Research Council/Pharmaceutical Manufacturers Association of Canada (MRC/PMAC), NHRDP, Bayer Inc., and the British Columbia Health Research Foundation. Core funding for Phase 3 was provided by the Canadian Institutes of Health Research (CIHR). Supplementary funding for the caregiver component was also obtained from CIHR. Additional funding was provided by Merck-Frosst and by Janssen-Ortho. The CSHA was coordinated through the University of Ottawa and Health Canada.

We thank Truls Østbye for providing a copy of the CSHA data. We also thank Carolyn Clark and Runa E. Steenhuis for their comments on an earlier version of this paper.