Combined Effects of Diabetes and Education on Decline of Cognitive Performance in the Older Population: The Survey of Health, Ageing, and Retirement in Europe

Abstract

Aims: Diabetes management requires cognitive abilities. Unfortunately, diabetes is a risk factor for cognitive decline. However, the effects of diabetes in persons with reduced cognitive reserves are unclear. We aimed to examine whether the effects of diabetes and education on cognitive skills simply add up or deviate from simple additivity. Methods: We used data from waves 1 to 7 (except wave 3) of the Survey of Health, Ageing, and Retirement in Europe (SHARE) collected between 2004 and 2017. SHARE includes 140,000 persons aged ≥50 years from 28 European countries and Israel. Diabetes was assessed by self-report and education was coded according to the International Standard Classification of Education levels. Verbal fluency, immediate, and delayed memory were assessed using standard tests. Interaction between diabetes and education was estimated from interaction contrasts and from interaction terms in adjusted regression models. Results: At baseline, cognitive performance declined in the order “no diabetes/high education” > “diabetes/high education” > “no diabetes/low education” > “diabetes/low education” for all three tests – e.g., the first group named 21.4 ± 7.2, the fourth group 14.6 ± 6.1 animals in a minute in the test of verbal fluency. Interaction contrasts and regression coefficients of interaction terms were close to zero, showing that the effects of diabetes and education on cognitive performance added up without interaction both in cross-sectional and longitudinal analyses. Conclusion: We have observed no interaction between education and diabetes on cognitive skills. Yet, people with diabetes and low education showed poor cognitive performance and should receive particular support in managing diabetes.