Long term prognostic implication of newly detected abnormal glucose tolerance among patients with stable cardiovascular disease: a population-based study

Abstract

Background: To assess the association between fasting plasma glucose (FPG) and 2-h post challenge plasma glucose (2h-PCPG) as continuous or categorical variables with risk of recurrent cardiovascular disease (CVD) and incident diabetes among subjects with history of previous CVD. Methods: In a prospective population-based cohort, a total of 335 Iranians aged ≥30 years, with history of CVD and free of known diabetes were included. Prediabetes was defined as impaired fasting glucose (IFG) according to the criteria of the American Diabetes Association (ADA) [IFG-ADA; FPG: 5.6-6.9 mmol/L], the World Health Organization (WHO) expert group (IFG-WHO; FPG: 6.1-6.9 mmol/L) and impaired glucose tolerance [IGT: 2h-PCPG: 7.8-11.0 mmol/L]. Cox’s proportional hazard models adjusted for traditional risk factors were used to estimate the hazard ratio (HR) with 95% confidence interval (CI) of different glucose intolerance for outcomes of interest. Results: During a median follow-up of 15.8 (IQR, 10.7-16.5) years, 178 CVD (hard event including death, myocardial infarction and stroke=69) events occurred. Regarding FPG, only IFG-ADA was associated with significant higher risk of hard CVD in the fully adjusted model (HR, 1.73, 95% CI: 1.04-2.89). Moreover, newly diagnosed diabetes (FPG≥7 mmol/L) was an independent risk of CVD (2.11: 1.22-3.66). Focusing on 2h-PCPG, subjects with newly diagnosed diabetes (2h-PCPG ≥ 11.1 mmol/L) had moderately increased risk of hard coronary heart disease (2.02:0.91-4.47, P=0.08). The multivariate HRs (95% CI) associated with 1 SD increase in FPG and 2h-PCPG was 1.16 (1.01–1.33) and 1.19 (1.02–1.38) for CVD, respectively. Among population free of diabetes at baseline (n=270), IFG-ADA, IFG-WHO and IGT were significantly associated with incident diabetes in multivariate analysis (all HRs > 4, P< 0.001); significant associations were also found for FPG and 2h-PCPG as continuous variables (all HRs for 1-SD increase > 2, all P < 0.001). Conclusions: Among subjects with stable CVD, both FPG and 2h-PCPG as continuous variables was associated with higher risk of recurrent CVD. However, only IFG-ADA was independent predictor of hard CVD events. Also, newly diagnosed diabetes, using FPG criteria, was associated with a significant risk of CVD. IFG-ADA, IFG-WHO and IGT were all significant predictors of incident diabetes.