Changes in body mass index and waist circumference as predictors of incident prediabetes: the Aichi Workers’ Cohort Study

Increases in body mass index (BMI) and waist circumference (WC) are established predictors of diabetes, yet the extent to which longitudinal changes in these measures signal emerging prediabetes is less clear. This study evaluated whether changes in BMI and WC predict incident prediabetes in a working‑age population. A total of 2,754 Japanese civil servants from the Aichi Workers’ Cohort Study were followed from 2013 to 2022. Individual slopes for changes in BMI and WC were derived from annual measurements collected between 2008 and 2013. Cox proportional hazards models estimated associations between slopes of anthropometric change and prediabetes onset, adjusting for demographic, lifestyle, and clinical factors, including initial (2008) BMI and WC. Over a median 7.0‑year follow‑up, 846 participants developed prediabetes (incidence rate: 50.1 per 1,000 person‑years). Each one‑standard‑deviation increase in BMI‑change slope was associated with a higher risk of prediabetes (HR 1.12; 95% CI, 1.05–1.20), with a comparable association observed for WC‑change slope (HR 1.12; 95% CI, 1.05–1.20). Progressive increases in BMI and WC were independently associated with higher prediabetes risk. Routine monitoring of longitudinal anthropometric change may support early identification of metabolic risk and guide low‑cost prevention strategies.