The relationship between the level of exercise and hemoglobin A1c in patients with type 2 diabetes mellitus: a systematic review and meta-analysis

Purpose The aim of the study was to evaluate the relationship between changes in hemoglobin A 1 c (HbA 1c ) and exercise levels in type 2 diabetes mellitus (T2DM) patients when performing various types of exercise. Methods The inclusion criteria were randomized controlled trials involving adults with T2DM, intervention involving exercise alone, the overall duration of intervention ≥12 weeks, and reporting HbA 1c . Weighted mean difference (WMD) was defined as the mean difference between the intervention group and the control group weighted by the inverse of the squared standard error for each study, and all WMDs were pooled as overall effects. A meta-regression analysis was performed to evaluate the relationship between the exercise level and the WMD in HbA 1c . Results Forty-eight studies (2395 subjects) were analyzed. The pooled WMD in HbA 1c decreased significantly (−0.5% [95% confidence intervals: −0.6 to −0.4]) but contained significant heterogeneity ( Q = 103.8, P 0.05; I 2 = 14.7%). Conclusions The exercise intervention decreases HbA 1c in T2DM patients. In addition, exercise for an extended duration was associated with an increase in HbA 1c , so the effects of exercise may be evident early on, but results suggested that exercise for a prolonged period alone may increase HbA 1c .