Glycated Hemoglobin and All-Cause and Cause-Specific Mortality Among Adults With and Without Diabetes

Context: The patterns of associations between glycated Hb (HbA(1c)) and mortality are still unclear. Objective: To explore the extent to which ranges of HbA(1c) levels are associated with the risk of mortality among participants with and without diabetes. Design, Setting, and Patients: This was a nationwide, community-based prospective cohort study. Included were 15,869 participants (median age 64 years) of the Health and Retirement Study, with available HbA(1c) data and without a history of cancer. Cox proportional hazards regression models were used to estimate hazard ratios with 95% Cls for mortality. Results: A total of 2133 participants died during a median follow-up of 5.8 years. In participants with diabetes, those with an HbA(1c) level of 6.5% were at the lowest risk of all-cause mortality. When HbA(1c) level was <5.6% or >7.4%, the increased all-cause mortality risk became statistically significant as compared with an HbA(1c) level of 6.5%. As for participants without diabetes, those with an HbA(1c) level of 5.4% were at the lowest risk of all-cause mortality. When the HbA(1c) level was <5.0%, the increased all-cause mortality risk became statistically significant as compared with an HbA(1c) level of 5.4%. However, we did not observe a statistically significant elevated risk of all-cause mortality above an HbA(1c) level of 5.4%. Conclusions: A U-shaped and reverse J-shaped association for all-cause mortality was found among participants with and without diabetes. The corresponding optimal ranges for overall survival are predicted to be 5.6% and 7.4% and 5.0% and 6.5%, respectively.