HbA1c and Mortality
A recently published study investigated the relationship of HbA1c levels with all-cause mortality in 15,869 patients with and without diabetes who participated in the Health and Retirement Study. Participants had a median age of 64 years and were followed for a median of 5.8 years. Cox proportional hazards regression models were used to estimate hazard ratios with 95% CIs for mortality.
Participants with diabetes who had an HbA1c level of 6.5% had the lowest risk for all-cause mortality. Participants with HbA1c less than 5.6% or greater than 7.4% had significantly increased risk for all-cause mortality compared with those with HbA1c of 6.5%.
Participants without diabetes who had an HbA1c level of 5.4% had the lowest risk for all-cause mortality. Participants with HbA1c less than 5.0% had significantly increased risk for all-cause mortality compared with those with HbA1c of 5.4%. A low HbA1c level in individuals without diabetes may be an indicator of poor health due to malnutrition, anemia, liver disease or the early stage of a chronic disease.
The researchers did not find a statistically significant increase in all-cause mortality risk for participants without diabetes who had HbA1c greater than 5.4%. Interestingly, mortality was not increased in individuals with HbA1c levels between 5.7% and 6.4%, which are classified as prediabetic by the American Diabetes Association.
This study revealed a U-shaped and a reverse J-shaped association of HbA1c with all-cause mortality among participants with and without diabetes. Researchers concluded that the optimal HbA1c range is 5.6% to 7.4% for patients with diabetes, 5.0% to 6.5% for patients without diabetes.
Reference
Li FR, Zhang XR, Zhong WF, et al. Glycated hemoglobin and all-cause and cause-specific mortality among adults with and without diabetes [published online March 21, 2019]. J Clin Endocrinol Metab. doi:10.1210/jc.2018-02536
