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Database of Abstracts of Reviews of Effects (DARE): Quality-assessed Reviews [Internet]. York (UK): Centre for Reviews and Dissemination (UK); 1995-.

Database of Abstracts of Reviews of Effects (DARE): Quality-assessed Reviews [Internet].

Lifestyle interventions for patients with and at risk for type 2 diabetes: a systematic review and meta-analysis

E Sumamo Schellenberg, DM Dryden, B Vandermeer, C Ha, and C Korownyk.

Review published: 2013.

CRD summary

The authors concluded that complex lifestyle interventions were effective in decreasing the incidence of type 2 diabetes in high-risk adults; the evidence was less clear for patients with type 2 diabetes. The authors' conclusions reflect the evidence, but this was limited, with statistical variation across trials of high-risk adults, so their conclusions for this population may be overstated.

Authors' objectives

To assess the effectiveness of complex lifestyle interventions, for adults with, or at risk of, type 2 diabetes.

Searching

Five electronic databases, including MEDLINE, EMBASE, and Cochrane Central Register of Controlled Trials (CENTRAL), were searched, for English-language articles, from 1980 to March 2010. MEDLINE and CENTRAL searches were updated to June 2013. Search strategies were reported. Clinical trial registries and reference lists of relevant articles were manually searched.

Study selection

This review was part of a report (see Other Publications of Related Interest) that included four conditions (type 2 diabetes, metabolic syndrome, breast cancer, and prostate cancer); this paper relates to type 2 diabetes only.

Eligible for inclusion were randomised controlled trials (RCTs) of the effectiveness of complex lifestyle interventions, compared with standard care. Outcomes had to be minimising progression to diabetes, for high-risk adults (as defined in the review), or prevention of diabetic complications, for adults (18 years or older) with type 2 diabetes. Complex lifestyle interventions had to include exercise, diet, and at least one other component. Standard care could be usual care, diet or exercise alone, or a waiting list. Interventions had to last at least three months, with a minimum of six months of follow-up; or last at least one year (no minimum follow-up). Secondary outcomes were stated.

In the included trials, the mean age of participant groups ranged from 44 to 67 years (based on supplementary table 2). Where reported, the mean body mass index (BMI) ranged from 26.2kg per m² to 38.3kg per m². Additional components varied across trials; including group or individual counselling, behaviour modification, and use of medication. The duration of interventions without follow-up ranged from 12 to 36 months, or it ranged from six to 72 months, with follow-up between three and 20 years. Interventions were delivered by a variety of people, including dietitians, nurses or multidisciplinary teams.

Two reviewers independently screened studies for inclusion. Disagreements were resolved through consensus or by referral to a third reviewer.

Assessment of study quality

Two reviewers independently assessed trial quality, using the Cochrane risk of bias tool. Discrepancies were resolved through consensus or by referral to a third reviewer.

The strength of evidence was assessed using the criteria of the Agency for Healthcare Research and Quality; for risk of bias, consistency, directness, and precision. Evidence was assessed as high, moderate, low, or insufficient strength.

Data extraction

One reviewer extracted the outcome data to calculate mean differences or risk ratios, and their 95% confidence intervals. Hazard ratios were reported for some outcomes. These data were checked by a second reviewer, with discrepancies resolved by consensus or by referral to a third reviewer.

Methods of synthesis

Where studies were sufficiently similar, a random-effects model was used to pool the data to calculate mean differences, standardised mean differences, or risk ratios, and their 95% confidence intervals. Where zero events were reported for any group, 0.5 was added to every group for that study. Statistical heterogeneity was assessed using X² and I².

Sensitivity analysis was conducted, for patients with diabetes, to assess the effects of lifestyle interventions with or without medication. Where meta-analysis was not possible, the data were presented in a narrative.

Results of the review

Twenty trials were included in the review (12,297 participants; range 39 to 5,145). Five trials were at high risk of bias; the risk in the remaining 15 trials was unclear.

High-risk adults: Nine trials assessed high-risk participants. Compared with control, there was moderate strength evidence indicating that lifestyle interventions statistically significantly slowed progression to type 2 diabetes, at the end of the intervention (RR 0.35, 95% CI 0.14 to 0.85; four RCTs), but there was evidence of statistical heterogeneity (I²=68%). This difference was maintained up to 10 years (RR 0.80, 95% CI 0.74 to 0.88; one RCT); the forest plot was inconsistent. The strength of evidence was low or insufficient for other outcomes, including secondary outcomes.

Adults with diabetes: Eleven trials assessed patients with type 2 diabetes. There was low strength evidence indicating no statistically significant differences between the intervention and control groups, for all-cause mortality, at more than 10 years of follow-up (two RCTs), but there was evidence of significant statistical heterogeneity (I²=62%). The strength of evidence was low or insufficient for the remaining outcomes, including secondary outcomes.

Sensitivity analysis: Interventions that did not include pharmacotherapy reported no improvement in any metabolic outcome (for example, blood pressure, or lipid levels), while interventions with pharmacotherapy significantly improved lipid levels (MD 0.04, 95% CI 0.03 to 0.05; three RCTs) and glycated haemoglobin levels (MD -0.71, 95% CI -1.31 to -0.12; three RCTs), at the end of intervention. Further results were reported in an appendix.

Authors' conclusions

Lifestyle interventions that included exercise, diet, and at least one other component were effective in decreasing the incidence of type 2 diabetes in high-risk adults, and this was maintained beyond the intervention. The evidence was less clear for patients with type 2 diabetes, with no evidence of benefit for mortality.

CRD commentary

The review question and inclusion criteria were clearly defined. A satisfactory search was undertaken, but as there were language restrictions, language bias cannot be ruled out. Trial quality was assessed, and this indicated high or unclear risk of bias in the individual trials. Each stage of the review process was performed in by two people, minimising the potential for reviewer error and bias.

Intervention and control groups varied considerably across the trials. Statistical heterogeneity was assessed using appropriate measures, which indicated high heterogeneity for some primary outcomes. The authors acknowledged that the review was limited by the inclusion of evidence of low or insufficient strength, a lack of direct evidence for patient-related outcomes, and a lack of consistency and precision among trials. They stated that most trials focused on surrogate measures, for which the clinical relevance was unclear. They also acknowledged that it was not possible to identify which additional intervention components were beneficial.

The authors' conclusions reflect the evidence, but this evidence was limited and there was statistical heterogeneity across trials in high-risk adults, so their conclusions for this population may be overstated.

Implications of the review for practice and research

Practice: The authors did not state any implications for practice.

Research: The authors stated that a systematic review of cohort studies could provide data on the effect of different lifestyle interventions, to assess their long-term sustainability and comparative effectiveness.

Funding

Funded by the Agency for Healthcare Research and Quality, USA.

Bibliographic details

Sumamo Schellenberg E, Dryden DM, Vandermeer B, Ha C, Korownyk C. Lifestyle interventions for patients with and at risk for type 2 diabetes: a systematic review and meta-analysis. Annals of Internal Medicine 2013; 159(8): 543-551. [PubMed: 24126648]

Other publications of related interest

Sumamo E, Ha C, Korownyk C, Vandermeer B, Dryden DM. Lifestyle interventions for four conditions: type 2 diabetes, metabolic syndrome, breast cancer, and prostate cancer. Rockville, MD, USA: Agency for Healthcare Research and Quality. Technology Assessment. 2011.

Indexing Status

Subject indexing assigned by NLM

MeSH

Diabetes Complications /prevention & control; Diabetes Mellitus, Type 2 /epidemiology /prevention & control; Diet; Exercise; Humans; Incidence; Life Style; Risk Factors

AccessionNumber

12013060056

Database entry date

23/10/2013

Record Status

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.

CRD has determined that this article meets the DARE scientific quality criteria for a systematic review.

Copyright © 2014 University of York.

PMID: 24126648

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