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% CIs 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.