A systematic review and meta-analysis of exercise interventions in adults with type 1 diabetes

Aims: Conflicting evidence exists regarding the benefits of physical activity for long-term blood glucose control in adults with type 1 diabetes (T1D). The object of this systematic review was to determine the effects of physical activity on long-term blood glucose control in T1D adults.

Methods: PubMed/Medline, Embase, CENTRAL, SPORTdiscus, Global Health and ICTRP were searched up to October 2013 for randomized trials of aerobic or resistance exercise training in T1D adults. Exercises had to be performed at least twice weekly for a minimum of two months. The primary outcome was glycated hemoglobin (HbA1c). Secondary outcomes included cardiorespiratory fitness and insulin dose.

Results: Six randomized trials were identified (323 adults); sample sizes ranged from n=6 to n=148 participants receiving the intervention. Five trials had an unknown risk of bias; one trial was deemed to be at high risk of bias. Exercise frequency varied from twice weekly to daily, with intensities (50-90% VO2peak), and session durations (20-120 min) varying widely. Four trials reported HbA1c, which decreased with exercise training (mean difference [MD] -0.78% (-9 mmol/mol), 95% CI -1.14 (-13 mmol/mol) to -0.41 (-5 mmol/mol); p<0.0001; I(2) 0%) compared with controls. Exercise training improved cardiorespiratory fitness by 3.45 ml/kg/min (95% CI 0.59 to 6.31, p=0.02, I(2) 0%) compared with controls. One trial reported an effect on insulin dose (MD -0.4U/kg, 95% CI -0.53 to -0.27, p<0.00001) compared to controls.

Conclusion: There are currently insufficient well-designed studies to ascertain the true effect of exercise training on HbA1c in individuals with T1D, but current results are promising.