The association between baseline and long-term status of metabolic score for insulin resistance index and the incidence of cardiometabolic multimorbidity

Cardiometabolic multimorbidity (CMM) significantly shortens life expectancy. This study aimed to explore the relationship between baseline and longitudinal metabolic score for insulin resistance index (METS-IR) and CMM incidence in middle-aged and elderly Chinese adults. The study included 8,050 participants for analysis. Long-term METS-IR status was assessed using two approaches: (1) the mean METS-IR calculated from two measurements and (2) the duration of high METS-IR exposure, categorized as 0, 2, or 4 years based on ROC-optimized cutoffs. The primary outcome was incident CMM, defined as the presence of at least two self-reported cardiometabolic conditions (diabetes, stroke, or cardiac disease). Multivariable logistic regression and nonparametric restricted cubic splines were employed to evaluate the risk and shape of the relationship between baseline and longitudinal METS-IR and CMM. During the 6-year follow-up, 540 participants developed CMM. Participants in the highest METS-IR tertile showed a significantly increased risk of developing CMM compared to those in the lowest tertile (baseline: OR 2.94, 95%CI 2.04–4.22; updated mean: OR 3.26, 95%CI 1.90–5.59). RCS analysis revealed a strong linear association for both baseline and updated mean METS-IR (both Plinearity<0.0001). Notably, participants with 2-year (OR 2.45, 95%CI 1.52–3.96) and 4-year (OR 3.46, 95%CI 2.18–5.51) high METS-IR exposure were associated with increased CMM risk compared to those with no exposure. Elevated baseline and long-term METS-IR, particularly sustained high exposure, were associated with higher CMM incidence in middle-aged and older Chinese adults.