Structured Exercise Training May Improve Glycemic Control

Laurie Barclay, MD

May 06, 2011

May 6, 2011 — Structured exercise training, including aerobic, resistance, or both, is linked to a greater reduction in hemoglobin A1c (HbA1c) levels in patients with diabetes, according to the results of a systematic review and meta-analysis reported in the May 4 issue of the Journal of the American Medical Association.

"Current guidelines recommend that patients with type 2 diabetes should perform at least 150 minutes per week of moderate-intensity aerobic exercise and should perform resistance exercise 3 times per week," write Daniel Umpierre, MSc, from the Hospital de Clinicas de Porto Alegre in Brazil, and colleagues. "Previous meta-analyses demonstrated that structured exercise training including aerobic and resistance exercises reduces ...HbA1c levels by approximately 0.6%. However, only 1 previous review separately analyzed associations of aerobic exercise, resistance training, and the combination of aerobic exercise and resistance training on change in HbA1c levels."

The investigators searched MEDLINE, Cochrane-CENTRAL, EMBASE, ClinicalTrials.gov, LILACS, and SPORTDiscus databases from January 1980 through February 2011 and retrieved 4191 articles. Inclusion criteria were enrollment of patients with type 2 diabetes in randomized controlled trials lasting at least 12 weeks that compared change in HbA1c levels with structured exercise training or physical activity advice vs a control group. Structured exercise training regimens could include aerobic and/or resistance training, or both, and physical activity advice could be given with or without dietary cointervention.

Two independent reviewers extracted data and evaluated quality of the 47 included randomized controlled trials, which enrolled a total of 8538 participants. A random-effects model allowed determination of pooled mean differences in HbA1c levels between the intervention and control groups.

Compared with control participants, those assigned to structured exercise training (23 studies) had a reduction in HbA1c level of −0.67% (95% confidence interval [CI], −0.84% to −0.49%; I2 , 91.3%). Furthermore, reductions in HbA1c levels vs control participants were observed with structured aerobic exercise (−0.73%; 95% CI, −1.06% to −0.40%; I2 , 92.8%), structured resistance training (−0.57%; 95% CI, −1.14% to −0.01%; I2 , 92.5%), and both combined (−0.51%; 95% CI, −0.79% to −0.23%; I2 , 67.5%).

Decrease in HbA1c levels was 0.89% for structured exercise durations of more than 150 minutes per week vs 0.36% for structured exercise durations of 150 minutes per week or less.

In 24 studies of physical activity advice, this particular intervention was associated with lower HbA1c levels vs the control group (−0.43%; 95% CI, −0.59% to −0.28%; I2 , 62.9%). For combined physical activity advice and dietary advice, reduction in HbA1c level vs control was −0.58% (95% CI, −0.74% to −0.43%; I2 , 57.5%), whereas physical activity advice alone was not associated with changes in HbA1c level.

"Structured exercise training that consists of aerobic exercise, resistance training, or both combined is associated with HbA1c reduction in patients with type 2 diabetes," the study authors write.

Limitations of this study include unblinded data extraction, creating potential bias; a high degree of heterogeneity in the meta-analyses; and generally low quality of the studies, reflecting an increased risk for bias in some studies.

"Additional information regarding the potential benefits of structured exercise is needed, including data from rigorously conducted clinical trials that provide information concerning the efficacy and cost-effectiveness of a structured physical exercise program across a broad spectrum of important health outcomes," Marco Pahor, MD, from the University of Florida, Gainesville, writes in an accompanying editorial. "In summary, [this meta-analysis] and cumulative evidence from a large number of [randomized controlled trials] conducted over the past few decades in the area of physical activity and exercise provide solid evidence for public policy makers to consider structured exercise and physical activity programs as worthy of insurance reimbursement to promote health, especially in high-risk populations."

Conselho Nacional de Desenvolvimento Científico e Tecnológico and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior partially supported this study. Two of the study authors have disclosed various financial relationships with Bristol-Myers Squibb, GlaxoSmithKline, Merck Sharp & Dohme, Servier, Abbott, Aventis, Bioassist, and/or Boehringer Ingelheim. Dr. Pahor is supported by grants from the National Institutes of Health.

JAMA. 2011;305:1790-1799, 1808-1809. Abstract Extract

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