Increased Hemoglobin A1c Time in Range Reduces Adverse Health Outcomes in Older Adults With Diabetes
Research Design and Methods: We conducted a retrospective observational study using administrative data from the Department of Veterans Affairs and Medicare from 2004 - 2016. Patients were ≥65 years old with diabetes and at least four A1c tests during a three-year baseline period. A1c TIR was the percentage of days during the baseline in which A1c was in an individualized target range (from 6.0-7.0% up to 8.0-9.0%) based on clinical characteristics and predicted life expectancy. Increasing A1c TIR was divided into categories of 20% increments and linked to mortality and cardiovascular disease (CVD) (i.e. myocardial infarction [MI] and stroke).
Results: The study included 402,043 Veterans (mean [SD] age, 76.9 [5.7] years; 98.8% male). During an average of 5.5 years of follow-up, A1c TIR had a graded relationship with mortality and CVD. Cox proportional hazards models showed lower A1c TIR was associated with increased mortality (A1c TIR 0-<20%; Hazard Ratio (HR) = 1.22; 95% CI, 1.20-1.25) and CVD (A1c TIR 0-<20%; HR = 1.14; 95% CI, 1.11-1.19) when compared to A1c TIR 80-100%. Competing risk models and shorter follow-up (e.g. 24 months) showed similar results.
Conclusion: In older adults with diabetes, maintaining A1c levels within individualized target ranges is associated with lower risk of mortality and CVD.