Abstract MP01: Midlife Diabetes and Lifetime Risk of Dementia: During 30 Years Follow-Up From the ARIC Study

Introduction: Diabetes is associated with both dementia and death. Ignoring the competing risk of mortality may result in overestimation of the lifetime of dementia. Hypothesis: The lifetime cumulative incidence of dementia associated with diabetes will be much lower when taking into account the competing risk of mortality, particularly at the oldest ages. Methods: We conducted a prospective cohort analysis of data from the Atherosclerosis Risk in Communities (ARIC) Study (midlife baseline at visit 2, 1990-1992). Diabetes was defined as a self-reported physician diagnosis, diabetes medication use, or HbA1C of 6.5% or greater. Incident dementia was ascertained via active surveillance involving interviews and adjudication. We conducted survival analysis using age as the time scale with age 50 as the origin and December 31st, 2019 as the administrative censoring date. Dementia risk was analyzed with death treated as a censoring event or as a competing risk. Results: Among 13,381 participants, 1798 (13.4%) had diabetes at baseline (mean age: 56.8 years). Using a standard Cox model, diabetes was associated with an increased hazard of dementia (HR 1.36; 95% CI 1.21, 1.52) and death (HR 1.87; 95% CI 1.76, 1.99). Censoring mortality (ignoring competing risk), diabetes was associated with a higher cumulative incidence of dementia at all ages ( Figure A ). Competing risk models showed a lower risk of dementia than models censoring death. Furthermore, diabetes was associated with a higher risk of dementia only before age 85 but a lower cumulative risk after age 85 due to the large excess risk of mortality ( Figures B and C ). Conclusion Standard methods dramatically overestimate the lifetime risk of dementia in persons with and without diabetes. Competing risk models are critical for accurate absolute risk estimates, particularly in the oldest ages. Interventions which increase life expectancy in patients with diabetes may increase the cumulative risk of dementia in old age.