The review concluded that there was no evidence for glycaemic benefit of exercise in patients with type 1 diabetes, as measured by glycosylated haemoglobin. The authors' conclusion reflects the evidence presented but its reliability is limited by small sample sizes, and statistical and clinical variation between studies; this limitation was acknowledged by the authors.

To review the evidence for a glycaemic benefit of exercise in patients with type 1 diabetes.

MEDLINE (to May 2012), EMBASE, The Cochrane library and SPORTDiscus were searched up to August 2011 with no language restriction. Search terms were reported. References of the retrieved articles were scanned. In addition, ClinicalTrials.gov, Current Controlled Trials Registry and the WHO hosted International Clinical Trials Registry Platform were searched for unpublished studies.

Eligible for inclusion were randomised and non-randomised controlled trials (RCTs) that evaluated interventions aimed at increasing exercise (supervised or unsupervised) compared with no intervention in adults and children with type 1 diabetes. If studies included an intervention other than exercise (for example dietary intervention), they were only eligible if they were given to both intervention and control arm. The primary outcome measure was change in glycosylated haemoglobin (HbA1c), and the secondary outcome measure was adverse event (hypoglycaemia).

Intervention duration ranged from 12 weeks to six months. Patient mean age ranged from 8.5 to 42 years. The weekly duration of the exercise ranged from 30 to 240 minutes.

Two reviewers independently selected the studies for inclusion in the review. Any disagreements were resolved through a meeting with two other reviewers.

The quality assessment for RCTs was based on guidance from the Centre for Reviews and Dissemination and included adequate sequence generation, allocation concealment, follow-up and exclusion biases, blinding of outcome assessors and intention to treat analysis. The quality assessment for non-RCTs included assessing any baseline differences in participants, biases in allocation, follow-up and exclusion and analytical method.

Study quality was assessed by one reviewer and checked by another reviewer.

Data were extracted to calculate mean differences and their 95% confidence intervals. Each trial measured the outcome of HbA1c before and after the intervention for both arms. One reviewer extracted the study data which was then checked by another reviewer. Authors were contacted for additional data.

A random-effects model was used to pool studies and calculate standardised mean differences. When there were multiple interventions, these interventions were combined into a single arm by estimating the weighted mean values. Statistical heterogeneity was assessed using Χ² and Ι². When heterogeneity was identified, subgroup analysis was performed for age and the study duration. Sensitivity analysis was performed to explore variations in randomised and non-randomised controlled trials. Publication bias was assessed using funnel plot analysis and Egger’s test.

Thirteen studies (eight RCTs and five non-RCTs) were included in the review. None of the studies reported randomisation sequence; only one study reported allocation concealment and blinding. Four out of eight studies used intention to treat analysis and most studies had a drop-out rate below 20%. Where reported, adherence to exercise training ranged from 62% to 100%.

The meta-analysis showed no statistically significant difference of changes in HbA1c in the intervention and control group (Ι²=57%; 12 studies, 452 patients). Similar results were found when age (child and young adults, eight studies; adults, four studies) and length of study duration were taking into consideration. Also sensitivity analysis showed no association between study design (RCT and non-RCT) and HbA1c reduction.

Mixed results were reported on hypoglycaemia (five studies). The funnel plot suggested evidence of publication bias.

This meta-analysis did not reveal evidence for a glycaemic benefit of exercise in people with type 1 diabetes as measured by HbA1c.

The review question and inclusion criteria were clear. No language or publication restrictions were applied, which reduced the potential for missed studies. Attempts were made to minimise reviewer errors and bias in the review process. Study quality was assessed using appropriate criteria. Statistical heterogeneity was assessed and appropriate methods were used to pool the results . Appropriate sensitivity and subgroup analyses were carried out.

The authors' conclusions reflected the reported evidence. The reliability of the conclusion is limited by small sample sizes together withstatistical and clinical heterogeneity between the included studies; this limitation was acknowledged by the authors.

Practice: The authors stated that even though the review did not detect a glycaemic benefit from exercise, there are other well defined benefits of exercise for patients with type 1 diabetes, such as reduction in macrovascular risk, mortality and improvement in wellbeing. The authors suggested that exercise should continue to play an important role in the management of type 1 diabetes.

Research: The authors stated that larger and longer (six months or longer) well-controlled randomised trials that examined the effect of exercise on glycaemic variability were needed. The study would also need to examine the effect of exercise intensity, different age groups, and duration of diabetes, as well as the incorporation of a dietary programme on glycaemic benefit.

No funding.

This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn.