Importance: Diabetes is a known risk factor for cardiovascular disease (CVD). Substantial uncertainty remains, however, about the relevance to CVD risk for blood glucose levels below the diabetes threshold.
Objective: To examine the association of random plasma glucose (RPG) levels with the risk for major CVD in Chinese adults without known diabetes.
Design, setting, and participants: This prospective cohort study included 467 508 men and women aged 30 to 79 years with no history of diabetes, ischemic heart disease (IHD), stroke, or transient ischemic attack. Participants were recruited from 5 urban and 5 rural diverse locations across China from June 25, 2004, to July 15, 2008, and followed up to January 1, 2014.
Exposures: Baseline and usual (longer-term average) RPG level.
Main outcomes and measures: Cardiovascular deaths, major coronary events (MCE) (including fatal IHD and nonfatal myocardial infarction), ischemic stroke (IS), major occlusive vascular disease (MOVD) (including MCE or IS), and intracerebral hemorrhage. Preliminary validation of stroke and IHD events demonstrated positive predictive values of approximately 90% and 85%, respectively. Cox regression yielded adjusted hazard ratios (aHRs) for CVD associated with RPG levels.
Results: Among the 467 508 participants (41.0% men; 59.0% women; mean [SD] age, 51 [11] years), a significant positive association of baseline RPG levels with CVD risks continued to 4.0 mmol/L (72 mg/dL). After adjusting for regression dilution bias, each 1-mmol/L (18-mg/dL) higher usual RPG level above 5.9 mmol/L (106 mg/dL) was associated with an 11% higher risk for cardiovascular death (6645 deaths; aHR, 1.11; 95% CI, 1.10-1.13). Similarly strong positive associations were seen for MCE (3270 events; aHR, 1.10; 95% CI, 1.08-1.13), IS (19 153 events; aHR, 1.08; 95% CI, 1.07-1.09), and MOVD (22 023 events; aHR, 1.08; 95% CI, 1.07-1.09). For intracerebral hemorrhage, the association was weaker, but also significant (4326 events; aHR, 1.05; 95% CI, 1.02-1.07). These associations persisted after excluding participants who developed diabetes during follow-up.
Conclusions and relevance: Among adult Chinese without diabetes, lower RPG levels are associated with lower risks for major CVDs, even within a normal range of blood glucose levels.