Metabolic score for insulin resistance (METS-IR) and new-onset type 2 diabetes in a middle-aged and elderly population: a nationwide prospective cohort study and implications for primary care.

The metabolic score for insulin resistance (METS-IR) has emerged as a noninsulin-based index for the approximation of IR, yet longitudinal evidence supporting the utility of METS-IR in primary prevention of type 2 diabetes mellitus (T2DM) remains limited.We aimed to investigate the longitudinal association between METS-IR, which combines fasting plasma glucose (FPG), lipid profiles and anthropometrics that can be routinely obtained in resource-limited primary care settings, and incidence of new-onset T2DM.We conducted a closed-cohort analysis of a nationwide, prospective cohort of 7,583 Chinese middle-aged and older adults who were free of T2DM at baseline, sampled from 28 out of 31 provinces in China. We examined the characteristics of subjects stratified by elevated blood pressure (BP) at baseline and new-onset T2DM at follow-up. We performed Cox proportional hazard regression analysis to explore associations of baseline METS-IR with incident T2DM in subjects overall, and in subjects stratified by baseline BP. We also applied net reclassification improvement (NRI) and integrated discrimination improvement (IDI) to examine the incremental value of METS-IR.During a mean follow-up period of 6.3 years, T2DM occurred in 527 subjects, among which, two-thirds (63.0%, 95% confidence interval [CI]: 58.7% to 67.1%) had baseline FPG <110 mg/dL. A standard deviation unit increase in baseline METS-IR was associated with the first incidence of T2DM (adjusted hazard ratio [aHR]=1.33, 1.22 to 1.45, P<.001) in all participants. Similar results were obtained in subjects with normal baseline BP (aHR=1.41, 1.22 to 1.62, P<.001) and elevated baseline BP (aHR=1.29, 1.16 to 1.44, P<.001). The predictive capability for incident T2DM improved by adding METS-IR to FPG. In study subjects with new-onset T2DM whose baseline FPG <126 mg/dL and <110 mg/dL, 63.0% (95%CI, 60.0% to 65.9%) and 58.1% (95%CI, 54.3% to 61.9%) of subjects had baseline METS-IR above the cut-off values, respectively.METS-IR was significantly associated with new-onset T2DM regardless of baseline BP level. Regular monitoring of METS-IR on top of routine blood glucose in clinical practice may add to the ability to enhance the early identification of primary care population at risk for T2DM.