Safety and effectiveness of metformin plus lifestyle intervention compared with lifestyle intervention alone in preventing progression to diabetes in a Chinese population with impaired glucose regulation: a multicentre, open-label, randomised controlled trial.

BACKGROUND Impaired glucose regulation (defined as either impaired glucose tolerance or impaired fasting glucose) is an important risk factor for the development of diabetes. We aimed to evaluate the safety and effectiveness of metformin plus lifestyle intervention compared with lifestyle intervention alone in preventing diabetes in Chinese participants with impaired glucose regulation. METHODS We did a multicentre, open-label, randomised controlled trial at 43 endocrinology departments in general hospitals across China. Eligible participants were individuals with impaired glucose regulation (ie, impaired glucose tolerance or impaired fasting glucose, or both), men or women aged 18-70 years with a BMI of 21-32 kg/m2. Eligible participants were randomly assigned (1:1) via a computer-generated randomisation to receive either standard lifestyle intervention alone or metformin (850 mg orally once per day for the first 2 weeks and titrated to 1700 mg orally per day [850 mg twice per day]) plus lifestyle intervention. Block randomisation was used with a block size of four, stratified by glucose status (impaired fasting glucose or impaired glucose tolerance), hypertension, and use of any anti-hypertensive medication. Lifestyle intervention advice was given by investigators at all participating sites. The primary endpoint was the incidence of newly diagnosed diabetes at the end of the 2-year follow-up. Analysis was done using the full analysis set and per-protocol set. This study is registered with ClinicalTrials.gov, number NCT03441750, and is completed. FINDINGS Between April, 2017, and June, 2019, 3881 individuals were assessed for eligibility, of which 1678 (43·2%) participants were randomly assigned to either the metformin plus lifestyle intervention group (n=831) or the lifestyle intervention alone group (n=847) and received the allocated intervention at least once. During a median follow-up of 2·03 years, the incidence rate of diabetes was 17·27 (95% CI 15·19-19·56) per 100 person-years in the metformin plus lifestyle intervention group and 19·83 (17·67-22·18) per 100 person-years in the lifestyle intervention alone group. The metformin plus lifestyle intervention group showed a 17% lower risk of developing diabetes than the lifestyle intervention alone group (HR 0·83 [95% CI 0·70-0·99]; log-rank p=0·043). A higher proportion of participants in the metformin plus lifestyle intervention group reported adverse events than in the lifestyle intervention alone group, primarily due to more gastrointestinal adverse events. The percentage of participants reporting a serious adverse event was similar in both groups. INTERPRETATION Metformin plus lifestyle intervention further reduced the risk of developing diabetes than lifestyle intervention alone in Chinese people with impaired glucose regulation, showing additional benefits of combined intervention in preventing progression to diabetes without new safety concerns. FUNDING Merck Serono China, an affiliate of Merck KGaA, Darmstadt, Germany. TRANSLATION For the Chinese translation of the abstract see Supplementary Materials section.