Abstract Body (Do not enter title and authors here): Introduction: Diabetes is a leading cause of morbidity and mortality in the United States, causing an estimated 440,000 deaths among US adults in 2019. Establishing the relevance of diabetes diagnosis at various ages to mortality in the contemporary US population, both overall and among major demographic subgroups, may inform public health policy and strategy.

Methods: We aimed to quantify the association between age at diabetes diagnosis and all-cause and cardiovascular mortality among US adults using publicly-available data from the National Health Interview Survey 1997-2018, linked to the National Death Index through 2019. We used Cox regression adjusted for age, sex, race and ethnicity, educational attainment, smoking status, body-mass index, physical activity, and insurance coverage to estimate all-cause and cardiovascular mortality rate ratios overall, by sex, and by race and ethnicity.

Results: Among 601,467 included adults (56% female, 16% Hispanic and 14% non-Hispanic Black) there were 75,122 deaths during 6.6 million person-years of follow-up. Overall, the all-cause mortality rate ratio associated with diabetes diagnosed at ages 20-29, 30-39, 40-49, 50-59, 60-69, or 70-79 years were 3.87 (95% CI 3.47-4.32), 2.87 (2.68-3.07), 2.26 (2.16-2.36), 1.72 (1.65-1.79), 1.47 (1.41-1.53), and 1.26 (1.19-1.33), respectively. The corresponding cardiovascular mortality rate ratios were 5.02 (4.09-6.16), 3.37 (2.99-3.78), 2.88 (2.65-3.13), 1.94 (1.81-2.09), 1.53 (1.43-1.65), and 1.27 (1.15-1.40), respectively. Although these associations were similar by sex and by race and ethnicity, the age-specific prevalence of diabetes was greatest among non-White participants. Among individuals with diabetes diagnosed at ages 20-29, 30-39, 40-49, 50-59, 60-69, or 70-79 years, an estimated 74%, 65%, 56%, 42%, 32%, or 20% of deaths from any cause were attributable to diabetes.

Conclusion: Age at diabetes diagnosis was associated with all-cause and cardiovascular mortality in a dose-dependent and approximately log-linear manner. Although associations were similar across diverse demographic groups, age-specific diabetes prevalence was greatest among non-White individuals, leading to greater mortality burden. If these associations were interpreted as largely causal, diabetes accounted for more than half of all deaths among those diagnosed before age 50 years. Preventing, delaying, and appropriately managing diabetes could prevent substantial excess mortality among US adults.