Elevated Hemoglobin A1C is Significantly Associated with Decreased Post-Exercise Heart Rate Recovery in Patients with Diabetes Mellitus

Abstract

Heart Rate Recovery (HRR) has been associated with cardiovascular and all-cause mortality in both healthy individuals and those with diabetes. We examined the association between Hemoglobin A1C (HbA1c) and post-exercise HRR in patients with diabetes. Participants who were free from known cardiac disease or severe orthopedic problems referred to an exercise specialist for a fitness assessment. All participants underwent a graded exercise test using a standard Balke-ware protocol. HRR defined as the decrease in heart rate from peak exercise after one minute of a cool down walk at 2 mph and 0% incline. The most recent HbA1c (within three months) recorded for each patient. This study included 411 individuals with diabetes [age 45 ± 10, 269 (65%) males, 375 (91%) with type 2 diabetes, BMI 31 ± 6, 49% with BMI > 30 kg/m 2 ]. The mean HbA1c was 7.3% ± 1.6 (56 mmol/mol). The participants divided into 4 equal cohorts based on the quartiles of HRR. Using multiple logistic regression, adjusting for age, gender, BMI, metabolic equivalent, beta blocker usage, hypertension, and duration of diabetes, there was a significant association between HbA1c and odds of having a HRR in the lowest quartile, such that for every unit increase in HbA1c, there was 13% increase in odds of being in the lowest HRR quartile (adjusted odds ratio 1.125 [1.002, 1.264]). Among diabetic patients without known cardiac disease, poor glycemic control as measured by elevated HbA1c is significantly associated with decreased post-exercise HRR.