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

https://doi.org/10.1016/j.diabres.2014.09.038Get rights and content

Highlights

  • There are few published randomized controlled trials of exercise in type 1 diabetes.

  • Of those that are published, few meet the methodological rigor currently expected of randomized trials.

  • The results of existing trials are promising, but insufficient for ascertaining the effect of exercise training on HbA1c.

Abstract

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; I2 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, I2 0%) compared with controls. One trial reported an effect on insulin dose (MD −0.4 U/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.

Section snippets

Background

Regular physical activity is associated with multiple health benefits for individuals with type 1 diabetes (T1D) [1]. Increased physical activity is associated with a lower risk of complications and an increased life expectancy [2], however, more than 60% of adults with T1D do not achieve recommended levels of physical activity [3]. Children with T1D also face barriers to achieving recommended physical activity targets [4]. In addition to conventional barriers to exercise (i.e. lack of time,

Methods

Using a previously published protocol [14], a systematic review applying methodological approaches outlined in the Methodological Expectations of Cochrane Intervention Reviews [15] was conducted and reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses criteria [16]. An expert panel from multiple fields (pediatrics, endocrinology, clinical epidemiology, exercise physiology) formulated the review question, reviewed the search strategies and review methods,

Results

Of the 14,663 citations obtained from electronic and hand-searches, 51 trial reports that potentially examined the effect of exercise on glycemic control in T1D individuals were identified. Forty-three reports were excluded: inappropriate population (n = 5); inappropriate intervention/control (n = 2); inappropriate study design (n = 21); full-text manuscripts unavailable for review through library services (n = 13); unable to translate non-English language (n = 2) (Fig. 1). Six unique trial reports [12],

Discussion

The current systematic review and meta-analysis supports observations of previous meta-analyses [10], [11], [13]. First, very few (only four) published randomized controlled trials could be identified comparing the effects of longer-term (i.e. >8 weeks) exercise training on HbA1c to performing no exercise in adults with T1D. Second, regular exercise training performed at least twice weekly for a minimum of eight weeks would appear to contribute to a significant absolute reduction in HbA1c in

Contribution statement

The authors contributed in the following ways: conception and design (AMAS, JM, SM), literature screening and conflict resolution (JH, JM, JY), analysis and interpretation of data (AMAS, JM), drafting the article (AMAS, JH, JY) or providing important revisions (JM, SM). All authors approved of the final version of the article.

Funding sources

Financial support for this systematic review was provided through the Robert Wallace Cameron Chair in Evidence-based Child Health (Grant # PEDS-311740), Manitoba Health Research Council and the Lawson Foundation (Grant # GRT 2012-059). JY was supported by a Manitoba Health Research Council/Manitoba Institute of Child Health Postdoctoral Fellowship and a Canadian Institutes of Health Research Postdoctoral Fellowship MFE: 131495. JMM is supported by a New Investigator Award from the Canadian

Conflicts of Interest statements

The authors have no conflicts of interest to declare.

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