Real-world LSM strategies can reduce diabetes risk, even with small weight reductions.

IMPORTANCE Diabetes prevention is imperative to slow worldwide growth of diabetes-related morbidity and mortality. Yet the long-term efficacy of prevention strategies remains unknown.OBJECTIVE To estimate aggregate long-term effects of different diabetes prevention strategies on diabetes incidence.DATA SOURCES Systematic searches of MEDLINE, EMBASE, Cochrane Library, and Web of Science databases. The initial search was conducted on January 14, 2014, and was updated on February 20, 2015. Search terms included prediabetes, primary prevention, and risk reduction.STUDY SELECTION Eligible randomized clinical trials evaluated lifestyle modification (LSM) and medication interventions (>6 months) for diabetes prevention in adults (age Ն18 years) at risk for diabetes, reporting between-group differences in diabetes incidence, published between January 1, 1990, and January 1, 2015. Studies testing alternative therapies and bariatric surgery, as well as those involving participants with gestational diabetes, type 1 or 2 diabetes, and metabolic syndrome, were excluded. DATA EXTRACTION AND SYNTHESISReviewers extracted the number of diabetes cases at the end of active intervention in treatment and control groups. Random-effects meta-analyses were used to obtain pooled relative risks (RRs), and reported incidence rates were used to compute pooled risk differences (RDs). MAIN OUTCOMES AND MEASURESThe main outcome was aggregate RRs of diabetes in treatment vs control participants. Treatment subtypes (ie, LSM components, medication classes) were stratified. To estimate sustainability, post-washout and follow-up RRs for medications and LSM interventions, respectively, were examined. RESULTS Forty-three studies were included and pooled in meta-analysis (49 029 participants; mean [SD] age, 57.3 [8.7] years; 48.0% [n = 23 549] men): 19 tested medications; 19 evaluated LSM, and 5 tested combined medications and LSM. At the end of the active intervention (range, 0.5-6.3 years), LSM was associated with an RR reduction of 39% (RR, 0.61; 95% CI, 0.54-0.68), and medications were associated with an RR reduction of 36% (RR, 0.64; 95% CI, 0.54-0.76). The observed RD for LSM and medication studies was 4.0 (95% CI, 1.8-6.3) cases per 100 person-years or a number-needed-to-treat of 25. At the end of the washout or follow-up periods, LSM studies (mean follow-up, 7.2 years; range, 5.7-9.4 years) achieved an RR reduction of 28% (RR, 0.72; 95% CI, 0.60-0.86); medication studies (mean follow-up, 17 weeks; range, 2-52 weeks) showed no sustained RR reduction (RR, 0.95; 95% CI, 0.79-1.14). CONCLUSIONS AND RELEVANCEIn adults at risk for diabetes, LSM and medications (weight loss and insulin-sensitizing agents) successfully reduced diabetes incidence. Medication effects were short lived. The LSM interventions were sustained for several years; however, their effects declined with time, suggesting that interventions to preserve effects are needed.

To develop and pilot test a taxonomy that empirically estimates health intervention effectiveness from efficacy data. Methods: We developed a taxonomy to score health interventions across 11 items on a scale from 0-100. The taxonomy was pilot-tested in efficacy and effectiveness diabetes prevention studies identified in two separate systematic reviews; here, the face validity, interrater reliability and factor structure of the taxonomy were established. Random effects meta-analyses were used to obtain weight loss and diabetes incidence pooled effects across studies. These effects and taxonomy scores were used to down calibrate efficacy estimates to effectiveness estimates as follows: Efficacy effect*[Efficacy score/highest possible score]. Results: We scored 82 effectiveness lifestyle modification studies (mean score 49.2), 32 efficacy lifestyle modification studies (mean score 69.8) and 20 efficacy studies testing medications (mean score 77.4). The taxonomy had face validity and good inter-rater reliability (ICC = 0.9 [0.87, 0.93]). The between-groups down calibrated weight loss estimate was similar to that observed in the effectiveness meta-analysis (1.7 and 1.8 kg, respectively). The down calibrated diabetes relative risk reduction was also similar to that observed in the effectiveness meta-analysis (30.6% over 2.7 years and 29% over 2 years, respectively). Conclusions: The taxonomy is a promising tool to estimate the real-world impact of health interventions.