Risk of non-fatal cardiovascular diseases in early-onset versus late-onset type 2 diabetes in China: a cross-sectional study

Background The age of onset of type 2 diabetes is decreasing. Because non-Chinese patients with early-onset type 2 diabetes (defined here as diagnosis at <40 years) have increased risk of vascular complications, we investigated effects of early-onset versus late-onset type 2 diabetes on risk of non-fatal cardiovascular diseases in China. Methods We did a cross-sectional survey using data from the China National HbA(1c) Surveillance System (CNHSS), including 222 773 Chinese patients with type 2 diabetes in 630 hospitals from 106 cities in 30 provinces of China in 2012. We documented demographic information and clinical profiles. Non-fatal cardiovascular disease was defined as non-fatal coronary heart disease or non-fatal stroke. Prevalence of non-fatal cardiovascular diseases was standardised to the Chinese population in 2011. We did logistic regression analysis to obtain odds ratios (ORs) for the risk of cardiovascular disease in patients with early-onset versus late-onset type 2 diabetes. Because the CNHSS did not contain patients on diet or lifestyle treatment alone, and did not capture information on smoking or lipid or antihypertensive treatment, we validated our findings in another dataset from a cross-sectional, multicentre observational study (the 3B study) of outpatients with type 2 diabetes to confirm that exclusion of patients with diet treatment only and non-adjustment for lipid-lowering and antihypertensive drugs did not introduce major biases in the main analysis. Findings Of 222 773 patients recruited from April 1, 2012, to June 30, 2012, 24 316 (11%) had non-fatal cardiovascular disease. Patients with early-onset diabetes had a higher age-adjusted prevalence of non-fatal cardiovascular disease than did patients with late-onset diabetes (11.1% vs 4.9%; p<0.0001). After adjustment for age and sex, patients with early-onset type 2 diabetes had higher risk of non-fatal cardiovascular disease than did those with late-onset type 2 diabetes (OR 1.91, 95% CI 1.81-2.02). Adjustment for duration of diabetes greatly attenuated the effect size for risk of non-fatal cardiovascular disease (1.13, 1.06-1.20). Results of the validation study showed that exclusion of patients with diet only and non-adjustment for lipid-lowering and antihypertensive drugs resulted in marginal changes in ORs for risk of non-fatal cardiovascular disease in patients with early-onset versus late-onset type 2 diabetes. Early-onset type 2 diabetes remained associated with increased risk of cardiovascular disease, attributable to longer duration of diabetes. Interpretation Chinese patients with early-onset type 2 diabetes are at increased risk of non-fatal cardiovascular disease, mostly attributable to longer duration of diabetes.