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Stepwise diabetes prevention program reduces risk in prediabetes

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August 10, 2016

Indian adults with prediabetes and overweight or obesity randomly assigned to a diabetes prevention program plus metformin therapy were less likely to develop type 2 diabetes at 3 years vs. controls, but RR reduction varied by prediabetes category, according to recent findings.

In a 3-year, randomized controlled trial, researchers found evidence of heterogeneity of effect across prediabetes type, with the strongest benefit observed in those with combined impaired fasting glucose and impaired glucose tolerance, followed by those with isolated IGT and isolated IFG.

“The program appeared to be less effective in people with [isolated] IFG,” Mary Beth Weber, PhD, MPH, assistant professor in the department of global health at Emory University, and colleagues wrote. “[Isolated] IFG may be a phenotype more related to poor insulin secretion and gluconeogenesis than to insulin resistance, and if so, lifestyle interventions may be insufficient because they target the wrong pathophysiological mechanism.”

Weber and colleagues analyzed data from 578 Indian adults with overweight or obesity and prediabetes participating in the Diabetes Community Lifestyle Improvement Program (D-CLIP), a randomized controlled, translation trial of adults with isolated IGT, isolated IFG, or IFG and IGT combined in Chennai, India (63.2% men; mean age, 44 years; mean BMI, 27.9 kg/m²). Within the cohort, 30.2% had isolated IFG, 29.7% had isolated IGT, and 40.1% had IFG plus IGT. Researchers assigned participants to a 6-month, culturally tailored, U.S. Diabetes Prevention Program-based lifestyle curriculum plus stepwise addition of metformin (500 mg, twice daily; n = 283) for participants at highest risk for conversion to diabetes at 4 months’ follow-up, or standard lifestyle advice, including a single day with one-on-one visits with a physician, dietitian and fitness trainer, plus one group class on diabetes prevention (controls; n = 295). For the intervention group, weekly classes included 16 core intervention classes in months 0 to 4 on active lifestyle changes, followed by eight maintenance classes in months 5 and 6.

Researchers assessed diabetes incidence biannually (either a single, annual oral glucose tolerance test or semiannual fasting plasma glucose test) and compared incidence across study arms using an intention-to-treat analysis (mean follow-up time, 2.54 years).

At 3 years, 25.7% of intervention participants developed diabetes vs. 34.9% of controls, for an average annual incidence of 7.8% vs. 11.1%. Researchers observed a 32% RR reduction in diabetes in intervention vs. control participants (95% CI, 7-50); the number needed to treat to prevent one case of diabetes was 9.8.

RR reduction varied by prediabetes type. Adults with IFG plus IGT saw a 36% RR reduction vs. 31% of isolated IGT and 12% for isolated IFG participants (P = .77).

Risk reduction also was stronger in participants aged 50 years or older and in men, whereas those with obesity were more than twice as likely to experience a reduction in diabetes incidence vs. those with overweight.

“Further analyses are needed to clarify the factors associated with this increased intervention success, but it is possible that obese individuals were more motivated to make the necessary lifestyle changes or that improved lifestyle, particularly increased physical activity, resulted in greater improvements in peripheral insulin sensitivity in the obese group,” the researchers wrote.

Most participants with baseline [isolated] IFG (76.5%) or IFG plus IGT (83%) required metformin therapy in addition to lifestyle intervention during the study; 51.3% of participants with [isolated] IGT required metformin therapy. – by Regina Schaffer

Disclosure: This study was supported by a BRiDGES grant from the International Diabetes Federation; BRiDGES is supported by an educational grant from Lilly Diabetes. Weber reports receiving funding from two National Institute of Diabetes and Digestive and Kidney Diseases’ grants.