The review concluded that robust behavioural change strategies were an essential part of an effective lifestyle modification programme. The quality of the included evidence and potential differences across the trials limit the reliability of the estimates of effectiveness, but the authors’ conclusions are suitably equivocal and seem reasonable but broad.

To assess behavioural change strategies for lifestyle modification in adults with type 2 diabetes prevention programmes.

PREMEDLINE/MEDLINE, EMBASE, CINAHL, PsycINFO and Cochrane Central Register of Controlled Trials (CENTRAL) were searched between 1966/inception and February 2009 for articles published in English. Search terms were reported. Trial websites, consensus statement, position stands and reviews were searched for relevant citations. A manual search of the reference lists of included articles was conducted.

Randomised controlled trials of exercise training/physical activity and/or nutritional interventions as a means of preventing diabetes versus control in adults at risk of type 2 diabetes were eligible for inclusion. The primary outcome was the incidence of type 2 diabetes. Trials that reported only intermediary outcomes (such as weight) were excluded.

The included trials studied combined exercise/physical activity and dietary intervention with the aim of achieving and/or maintaining weight loss versus usual care. Mean age ranged from 42 to 56 years. Frequency of exercise ranged from more than 150 minutes per week of moderate intensity exercise to 30 to 40 minutes of daily moderate exercise. Dietary interventions all involved fat intake reduction and most included portion control and decreased alcohol. The number of contacts with staff ranged from six or fewer to 165. Intervention durations ranged from one to six years.

The authors did not state how many reviewers performed study selection.

Trial quality was assessed by two reviewers who used the Delphi list. The authors considered study-specific quality items such as whether exercise was supervised and appropriate between-group statistical analyses.

Data were extracted on the incidence of type 2 diabetes and used to calculate relative risk reductions (RRR), absolute risk (AR), absolute risk reduction (ARR), together with 95% confidence intervals. The number needed to treat (NNT) was estimated. Effect sizes were defined as clinically important when relative risk reduction was at least 10%. Data on compliance and adherence were extracted.

Four reviewers independently extracted data. Discrepancies were resolved by consensus.

A narrative synthesis was presented. Studies were grouped by intervention.

Seven RCTs (5,825 patients) were included in the review. Loss to follow-up ranged from 6.9% to 13.4%. All trials reported baseline characteristics, used randomisation and reported confidence intervals or standard deviations; some studies did not report on baseline health status and adverse events. Most trials used intention-to-treat analysis.

Compared with control, the risk of type 2 diabetes was reduced with lifestyle modification interventions (RRR 29% to 75%, ARR 5.4% to 21.7%, NNT 4.6 to 18.5 individuals.)

Other results were presented in the review. It was not possible to estimate adherence and compliance.

Robust behavioural change strategies formed an essential part of an effective lifestyle modification programme.

Inclusion criteria for the review were broadly defined. Several relevant data sources were searched. There was potential for language bias, as only articles in English were included. Publication bias was not assessed and could not be ruled out, but the extensive search should have limited the risk. Attempts were made to reduce reviewer error and bias throughout data extraction and quality assessment; it was unclear whether similar attempts were made for study selection. Quality assessment was undertaken using a standard checklist and indicated the variable quality of the included trials (acknowledged by the authors).

The authors noted that types of intervention, cohort characteristics, outcomes and outcome measurement tools varied across trials. Given such differences it seems appropriate that the authors chose to narratively synthesise the evidence.

The quality of the included evidence and potential differences across the trials limit the reliability of the estimates of effectiveness, but the authors’ conclusions are suitably equivocal and seem reasonable but broad.

Practice: The authors stated that the results of the review may be clinically relevant when considering the implementation of type 2 diabetes programmes in a community setting.

Research: The authors stated a need for future research to estimate adherence/compliance and treatment goals. Research into the optimal number of contacts and type of contact was needed. Evidence on the effectiveness of programmes in the real world was needed and the outcomes of on-going studies were awaited eagerly.

None stated.

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.