Fasting plasma glucose and HbA(1c) in cardiovascular risk prediction: a sex-specific comparison in individuals without diabetes mellitus

This study aimed to assess the cardiovascular risk of individuals with fasting plasma glucose (FPG)- and/or HbA(1c)-defined prediabetes (5.6-6.9 mmol/l and 39-47 mmol/mol [5.7-6.4%], respectively) or manifest diabetes mellitus and to evaluate whether FPG or HbA(1c) can improve risk prediction beyond that estimated by the Systematic Coronary Risk Evaluation (SCORE) chart in individuals without diabetes mellitus. Cox regression was employed to estimate HRs for primary incident cardiovascular events (CVEs) in a cohort of 8,365 individuals aged 50-74 years. Furthermore, HbA(1c) and FPG were added individually to the variables of the SCORE and measures of model discrimination and reclassification were assessed. During 8 years of follow-up, 702 individuals had a primary CVE. After adjusting for conventional cardiovascular risk factors, HRs were attenuated close to one for the prediabetes groups (especially for women), whereas a 1.7- and a 1.9-fold increased risk persisted for men and women with diabetes, respectively. Extension of the SCORE variables by either FPG or HbA(1c) did not improve its predictive abilities in individuals without diabetes. There was a non-significant net reclassification improvement for men when HbA(1c) was added (2.2%, p = 0.16). The increased cardiovascular risk of individuals with FPG- or HbA(1c)-defined prediabetes can mainly be explained by other cardiovascular risk factors. Adding FPG or HbA(1c) did not significantly improve CVE risk prediction by the SCORE variables in individuals without diabetes mellitus.