Higher “normal” glycated hemoglobin levels were associated with increased risk for diabetes, CVD, stroke, and mortality in adults

Cohort study (Atherosclerosis Risk in Communities [ARIC] study) with follow-up visits at 3 and 6 years and then annual telephone follow-up to a median of about 14 years.

4 communities in the USA.

11 092 black or white adults (mean age 57 y, 58% women) who attended study visit 2 (enrollment for current cohort). Exclusion criteria included history of diabetes (self-reported or use of diabetes medication) or cardiovascular disease, validated cardiovascular event between study visits 1 and 2, or nonfasting at visit 2.

HbA_1c and fasting glucose levels. Analyses were adjusted for age, sex, race, lipid levels (high- and low-density lipoprotein cholesterol and triglycerides), body mass index, waist-to-hip ratio, hypertension, family history of diabetes, education level, alcohol use, smoking status, and physical activity level.

Diabetes, based on self-report or use of diabetes medication, mortality, coronary heart disease, and ischemic stroke.

Multivariate analyses showed that higher levels of baseline HbA_1c were associated with increased risk for diabetes (Table), coronary heart disease (hazard ratio [HR] for each 1% absolute increase 1.19, 95% CI 1.11 to 1.27), and ischemic stroke (HR 1.34, 95% CI 1.22 to 1.48) over 15 years. HbA_1c levels < 5% and ≥ 5.5% were associated with increased risk for mortality (Table). Results were similar after adjusting for baseline fasting glucose levels.

In middle-aged adults, higher “normal” levels of glycated hemoglobin were associated with increased risk for diabetes, coronary heart disease, ischemic stroke, and total mortality.