Elevated Hemoglobin A1cIs Associated With Incident Diabetes Within 4 Years Among Normoglycemic, Working-Age Individuals in an Employee Wellness Program
Assessment of hemoglobin A 1c (HbA 1c ) levels in addition to fasting glucose (FG) levels and other risk factors can improve diabetes risk assessment (1). Employee wellness programs (EWPs) are common in the U.S. (2), providing opportunities to identify working-age individuals at risk for diabetes (3) and to offer risk-reduction programs targeted to those at most risk. Based on the records of one large laboratory testing provider for EWPs, 25% of those offered FG testing were also offered HbA 1c
... also offered HbA 1c testing (4). Here we investigated whether the addition of HbA 1c to FG testing for EWP participants with apparently normal FG (,100 mg/dL) would identify those at elevated risk for incident diabetes. The analysis was based on a cohort of 34,676 employees and spouses who participated in an EWP in 2012. Those with baseline FG $100 mg/dL, HbA 1c $6.5% (48 mmol/mol), or a self-reported physician diagnosis of diabetes (n = 8,837), with missing baseline data (n = 244), or who failed to participate in the EWP at least once during 4 years of follow-up (n = 4,256) were excluded, leaving 21,339 participants. The association between baseline HbA 1c level and incident diabetes (FG $126 mg/dL or a self-reported physician diagnosis of diabetes in any annual follow-up EWP) was assessed in regression models that adjusted for age, sex, FG, triglyceride-to-HDL cholesterol ratio, serum creatinine, alanine aminotransferase, BMI, and blood pressure. In this population of working-age individuals without diabetes with normal FG, 513 participants had incident diabetes during 4 years of follow-up. Those with incident diabetes were older (46.1 6 9.9 years) than those without incident diabetes (43.7 6 11.0 years; P = 3 3 10 27 ). Of the 85% of participants who reported their ethnicity, 49% reported white, 17% Asian, 13% African American, 12% Hispanic, and 9% other. The cumulative rate of incident diabetes after median follow-up of 3.96 years was 0.74 (95% CI 0.68 to 0.80) per 100 person-years (cumulative incidence of 3.0%, 95% CI 2.7 to 3.2, at 4 years of follow up). Baseline HbA 1c levels were associated with incident diabetes (adjusted odds ratio [OR] 2.2, 95% CI 2.0 to 2.5, per SD; P = 4 3 10 262 ). Similar results were observed after further adjustment for ethnicity (OR 2.2, 95% CI 2.0 to 2.5). Those with the highest 5% of HbA 1c values had 8.4-fold greater risk of diabetes (adjusted OR 8.4, 95% CI 6.6 to 10.8) (Fig. 1 ) than those with normal HbA 1c levels. At the end of follow-up, the diabetes-free survival rate was 0.84 (95% CI 0.81 to 0.87) for those with HbA 1c .5.9% (41 mmol/mol) but ,6.5% (48 mmol/mol), and 0.98 (95% CI 0.98 to 0.99) for those with normal HbA 1c levels. Figure 1-Odds of incident diabetes according to HbA 1c level. ORs and 95% CIs for incident diabetes among EWP participants who were free of diabetes and who had FG ,100 mg/dL at baseline. The ORs were estimated in models that adjusted for age, sex, FG, triglyceride-to-HDL cholesterol ratio, serum creatinine, alanine aminotransferase, BMI, and blood pressure.