Type 2 Diabetes, Risk of Dementia and Cognitive Decline, and the Competing Risk of Mortality Among Middle-Aged and Older Adults

Type 2 diabetes is highly prevalent and has been linked with an increased risk of dementia and premature mortality. Earlier death among people with diabetes may impact the association between diabetes and dementia. This is particularly important for populations with a high burden of diabetes, including Mexican Americans and African Americans. The objective of this dissertation was to evaluate the association of diabetes with incidence of dementia and cognitive impairment without dementia (CIND) and cognitive decline in late-life among Mexican Americans and in mid-life among African Americans and whites while accounting for the competing risk of mortality. The study populations included: 1) a cohort of dementia-free older Mexican Americans (n=1617) aged 60-98 from the Sacramento Area Latino Study on Aging (SALSA) followed for 10 years beginning in 1998 and 2) a cohort of middle-aged African Americans and whites (n=1886) aged 48-70 from the Atherosclerosis Risk in Communities (ARIC) Study followed for 14 years beginning in 1990. The association between diabetes and incidence of dementia/CIND was examined with competing risk regression models in the SALSA cohort and the association between diabetes and cognitive decline was examined with joint longitudinal-survival models in the SALSA and ARIC cohorts. In the SALSA cohort, Mexican Americans with treated and untreated diabetes had an increased risk of dementia/CIND compared to those without diabetes (HR=2.05, 95% CI: 1.41-2.97 and HR=1.55, 95% CI: 0.93-2.58) after accounting for the competing risk of death. Additionally, Mexican Americans with diabetes experienced modestly accelerated cognitive decline compared to those without diabetes. In the ARIC cohort, earlier onset of diabetes was associated with greater cognitive decline in mid-life among African Americans. No association between diabetes and cognitive decline was observed among whites. These findings provide evidence that the association between diabetes and dementia/CIND among Mexican Americans remains strong after accounting for the competing risk of mortality. The association between diabetes and cognitive decline is less evident. Future research is needed to identify how diabetes treatments influence cognitive decline among people with diabetes