A cross-national comparison of the effect of diabetes on the cognitive function of older adults- The case of Mexico and the United States

Older adults in Mexico and the U.S. have aged under different socioeconomic and epidemiologic contexts. Poorer aging conditions in Mexico impact cognitive function and chronic disease burden. In Mexico, diabetes prevalence is similar to that in the U.S., but the diabetes-related mortality is higher. As diabetes impacts cognitive function, the greater diabetes burden in Mexico may negatively impact the cognitive function of older adults to a greater extent compared to the U.S. Thus, the objective of this dissertation is to measure the effect of diabetes on the cognitive trajectory of older adults in Mexico and the U.S at one cross-section and over time. Two nationally representative cohorts of older adults 50 years and older were used to study Mexico and the U.S., the Mexican Health and Aging Study (MHAS) and the Health and Retirement Study (HRS), respectively. The outcome of interest was cognitive function, measured with a total cognitive score, by cognitive domain, and categorized into dementia vs. normal cognition. The main independent variable was self-reported diabetes status. A cross-sectional analysis was conducted to assess how diabetes impacts cognitive function in the 2012 waves of the MHAS and HRS. Two longitudinal analyses were conducted using the 2001, 2003, 2012, and 2015 MHAS waves, and the 2000, 2002, 2012, and 2014 HRS waves. First, mixed-effect linear models were used to test the impact of diabetes on the cognitive trajectory in both countries. Second, GEE models were used to test if the risk of dementia associated with diabetes differed between countries. Compared to those without diabetes, the results showed that those with diabetes had lower cognitive scores in the 2012 cross-section in both countries. Diabetes also predicted greater cognitive decline over time in both countries, for both memory and non-memory domains. Further, having diabetes increased the risk of dementia at age 65, but the dementia risk did not differ by diabetes status after age 80 in both countries. Independent of diabetes status, the probability of dementia over time was greater in Mexico compared to the U.S. However, the risk of dementia associated with diabetes was similar between the two countries.