Elsevier

Metabolism

Volume 62, Issue 2, February 2013, Pages 303-314
Metabolism

Meta-analysis
Efficacy of lifestyle interventions in reducing diabetes incidence in patients with impaired glucose tolerance: A systematic review of randomized controlled trials

https://doi.org/10.1016/j.metabol.2012.07.009Get rights and content

Abstract

Objective

Every year over 3.8 million people are dying of diabetes and its complications. Lifestyle intervention was suggested to have beneficial effects in preventing and reducing diabetes incidence. Interventions in patients with impaired glucose tolerance (IGT), who belong to a high risk group in developing diabetes, are supposed to be especially effective. According to the evidence hierarchy, a 1a level of evidence is missing and therefore a systematic review verifying the efficacy of lifestyle intervention is needed.

Materials/Methods

Systematic review: The electronic database PubMed, Embase, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, and Health Technology Assessment database were searched. Main inclusion criteria were randomized controlled trials, impaired glucose tolerance, lifestyle intervention with control group and observation time > 6 months. Outcome measures were all diabetes events, as defined by the authors of each study, all-cause mortality, diabetes mortality, and quality adjusted life years (QALY). Two independent reviewers abstracted the studies by title, abstract and full-text analysis. Furthermore the reporting quality of each study was assessed by using the CONSORT criteria (Consolidated Standards of Reporting Trials) and the methodological quality by SIGN 50 instrument (Scottish Intercollegiate Guidelines Network methodology checklist for randomized controlled trials). The primary outcome measure was diabetes incidence. Secondary outcome measures were overall mortality, disease-specific mortality, quality adjusted life years (QALY), and clinical parameters; body mass index (BMI), weight change, blood pressure, blood parameter, smoking, alcohol consumption.

Results

7 trials which included 25 relevant publications were identified. Kappa Cohens for title-analysis were К = 0.77, (CI = 0.71–0.83), abstract-analysis К = 0.81 (CI = 0.64–0.92) and full-text analysis К = 0.78 (CI = 0.57–0.98). Overall 5663 patients were analyzed with primary follow-up time: India (3 y), Japan (4 y), Sweden (5 y), Da Qing (6 y), SIM (3 y), DPP (5 y), DPS (4 y) and drop-out rate ranges from 5% to 28%. Diabetes incidence ranges from 3% to 46% in the intervention group and 9.3% to 67.7% in the control group. The India study reported ARR = 16%, RRR = 29% (p = 0.018), Japan: ARR = 6.3%, RRR = 65% (p < 0.001), Sweden: ARR = 4%, RRR = 25% (p = not significant), Da Qing: ARR = 22%, RRR = 32% (p < 0.05), SLIM: ARR = 20%, RRR = 53% (p = 0.025), DPP: ARR = 15%, RRR = 58% (significant, no p-value reported), and DPS: ARR = 12%, RRR = 52% (significant, no p-value reported). Mortality and morbidity were only analyzed in Da Qing study which showed no statistical differences (overall mortality: HRR 0.96, CI 0.65–1.41, CVD-mortality: HRR 0.83; CI 0.48–1.40, CVD event: HRR 0.98; CI 0.71–1.37).

Conclusion

Under consideration of heterogeneity in lifestyle interventions and follow up time of the included studies, this systematic review illustrated that lifestyle intervention can have a beneficial effect on the incidence of diabetes in patients with impaired glucose tolerance. However, several studies found the effect of lifestyle intervention decreased after intervention was terminated. No long-term benefit in mortality and morbidity was found. Development of standardized lifestyle intervention program is strongly needed and further long-term intervention trials using this program are crucial in evidencing the long-term efficacy.

Introduction

Worldwide, the incidence of type 2 diabetes mellitus is increasing. The World Health Organization has predicted a global increase in diabetes prevalence of 39% between the years 2000 and 2030. The statistic shows that the number will increase to 366 million people in the year 2030 [1].

Type 2 diabetes results from the combination of genetic predisposition, behavioral, and environmental risk factors [2]. There is strong evidence that such modifiable risk factors like bad health behaviors, nutrition, obesity, and physical inactivity are the main environmental determinants of the disease [3], [4], [5], [6], [7], [8], [9].

Impaired glucose tolerance (IGT) is an intermediate category between normal glucose tolerance and diabetes. Subjects with impaired glucose tolerance have an increased risk of developing type 2 diabetes, and therefore form an important high-risk target group for intervention aimed at preventing diabetes [3], [10], [11].

Early studies involving lifestyle intervention showed beneficial effects in diabetes high risk groups [12], [13]. However there is no level of evidence 1 study to confirm the effect of lifestyle interventions in IGT patients. The aim of this study was to assess the efficacy of lifestyle intervention to prevent the onset of type 2 diabetes in IGT patients, using systematic review.

Section snippets

Search strategy and selection criteria

We conducted a systematic review of the available literature in accordance with the QUORUM guidelines and Cochrane Handbook for Systematic Reviews of Interventions [14], [15]. PICO criteria were used to construct the clinical questions [16], [17]. Inclusion and exclusion criteria were defined. Main inclusion criteria were impaired glucose tolerance (IGT), randomized controlled trial, lifestyle intervention with control group, observation time > 6 months and outcome defined as diabetes incidence.

Result

Overall, 7 randomized controlled trials (25 publications) were identified, in which they provide the information of a total of 5663 patients. The identified trials including follow-up time, drop-out rate, and patient characteristics at randomization are shown in Table 1. The flowchart in Fig. 1 shows the identification process. Kappa Cohens for title analysis were К = 0.77, (CI = 0.71–0.83), abstract-analysis К = 0.81 (CI = 0.64–0.92) and full-text analysis К = 0.78 (CI = 0.57–0.98). According to SIGN 50

Discussion

The main finding of this study is that all included studies found a reduction in diabetes type 2 incidence by lifestyle intervention in impaired glucose tolerance patients. The overall incidence of diabetes was reduced by 4% to 21.7% in the intervention group compared with the control group depending on the study and follow-up years. A significant decrease in mortality and morbidity rates was not reported. None of the included studies performed an analysis according to QALY parameters.

Similar

Conclusion

Consequently, this study added information on how lifestyle intervention produced significant improvement in diabetes incidence but no improvement in mortality, morbidity or other known risk factors for diabetic complications. However, according to the heterogeneity of study designs and multiple influence factors, this study can not give a definitive answer to the question of whether primary prevention of Type 2 diabetes reduces the diabetes incidence, but suggestions could be proposed. To

Author contributions

Uzung Yoon: designed and conduct of the study, data collection and analysis, data interpretation and manuscript writing.

Lai Lai Kwok: data collection and analysis, data interpretation and manuscript writing.

Athanasios Magkidis: data collection and analysis, data interpretation.

Role of the funding source

No funding

Funding

None.

Conflicts of interest

The authors declare that they have no competing interests including financially related interest.

Non-financial competing interests.

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