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Physical Activity Advice Only or Structured Exercise Training and Association With HbA1c Levels in Type 2 Diabetes: A Systematic Review and Meta-Analysis
Study Questions:
Is there an additional value of a structured exercise training program compared to physical activity advice with or without dietary interventions on change in glycated hemoglobin (HbA1c) in type 2 diabetics?
Methods:
The authors conducted a systematic review and meta-analysis of published randomized controlled clinical trials (RCTs) of at least 12 weeks’ duration that were designed to assess the utility of exercise interventions with or without dietary co-intervention on HbA1c in type 2 diabetics. Databases were searched from January 1980 through February 2011. Of 4,191 articles retrieved, 47 RCTs (8,538 patients) were included. Pooled mean differences in HbA1c levels between intervention and control groups were calculated using a random-effects model. Both statistical heterogeneity and publication bias were considered in the analysis.
Results:
Mean age ranged from 52 to 67 years. Study duration ranged from 12 to 52 weeks. The majority of programs recommended three sessions per week. Adherence rate was >75% in 14 of the 15 structured exercise studies. Dropout rate was <20% in 90% of all 47 RCTs. Overall, structured exercise training (23 studies) was associated with a decline in HbA1c level (−0.67%; 95% confidence interval [CI], −0.84% to −0.49%) compared with control participants. In addition, structured aerobic exercise (−0.73%; 95% CI, −1.06% to −0.40%), structured resistance training (−0.57%; 95% CI, −1.14% to −0.01%), and both combined (−0.51%; 95% CI, −0.79% to −0.23%) were each associated with declines in HbA1c levels compared with control participants. Structured exercise durations of more than 150 minutes per week were associated with HbA1c reductions of 0.89%, whereas structured exercise durations of 150 minutes or less per week were associated with HbA1c reductions of 0.36%. Overall, interventions of physical activity advice (24 studies) were associated with lower HbA1c levels (−0.43%; 95% CI, −0.59% to −0.28%) compared with control participants. Combined physical activity advice and dietary advice was associated with decreased HbA1c (−0.58%; 95% CI, −0.74% to −0.43%), as compared with control participants. Physical activity advice alone was not associated with HbA1c changes.
Conclusions:
Structured exercise training that consists of aerobic exercise, resistance training, or both is associated with HbA1c reduction in patients with type 2 diabetes. Structured exercise training of more than 150 minutes per week is associated with greater HbA1c declines than that of 150 minutes or less per week. Physical activity advice is associated with lower HbA1c, but only when combined with dietary advice.
Perspective:
The value of structured lifestyle interventions for diabetes, abnormal fasting blood sugar, hypertension, and coronary artery disease has each has been demonstrated in controlled studies. The challenge to the health care industry is to find ways to provide the intervention in large numbers of patients in a cost-effective manner and how to improve adherence. Use of cardiac rehab facilities, equipment, and personnel would seem to be a logical solution. The message that more is better and structured exercise is necessary to impact glycemic control is not surprising since compliance with physical activity advice without coaching and accurate monitoring of adherence is usually unsuccessful.
Keywords: Glycated Hemoglobin A, Resistance Training, Coronary Artery Disease, Health Care Sector, Blood Glucose, Exercise, Diabetes Mellitus, Type 2, Hypertension, Fasting
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