Insulin resistance is associated with incident prediabetes and type 2 diabetes in normoglycemic individuals

Testing insulin resistance could help improve physician assessment of patients' risk of prediabetes or type 2 diabetes (T2D), even among normoglycemic individuals.

The longitudinal study followed 16,333 normoglycemic participants in a nation-wide employer-sponsored health assessment program starting in August 2020 with a median follow-up time of 2.9 years for incident prediabetes or T2D. The probability of insulin resistance (IRRS) was calculated from fasting intact insulin and C-peptide serum levels. Incident events had fasting plasma glucose level ≥100 mg/dL (≥5.6 mmol/L), HbA1c ≥ 5.7 % (≥38.8 mmol/mol), or a self-reported physician diagnosis of T2D.

The study population had a median age of 43 years at baseline (31 % men). IRRS was <8 % for participants in the bottom tertile of the distribution compared with >20 % for those in the top tertile. Participants in the top tertile of IRRS had 43 % greater risk of incident prediabetes or T2D (adjusted hazard ratio, aHR = 1.43 [95 % CI, 1.31-1.57], P < 0.001) compared with those in the bottom tertile, in a model that adjusted for age, sex, BMI, and HbA1c.

Elevated IRRS is associated with incident prediabetes or T2D regardless of established risk factors. Evaluating insulin resistance in normoglycemic patients may improve T2D prevention efforts.