Clinical Characteristics Of Patients With Different Durations Of Type 2 Diabetes Mellitus

Objectives Although type 2 diabetes mellitus(T2DM) shortens life expectancy by 10-12 years, some patients still survive an extreme long duration of disease. Clinical characteristics of Chinese patients with over 40 years of T2DM remained unknown. This study aimed to investigate: 1). to explore the association between vascular complications in patients with T2DM and its duration, so to provide basic data for early identification, early diagnosis and early intervention of diabetes complications; and 2). to document clinical characteristics of Chinese patients with 40 and more years of T2DM.Methods The China National Hb A1c(Glycated Hemoglobin) Surveillance System(CNHSS) recruited 222,773 patients with T2DM who were seeking outpatient care from 417 hospitals between March 2012 and June 2012. We selected a random sample of 22389 patients from the large database. The major included criteria were 18 years of age or more and treated with oral antidiabetes drugs(OADs) alone or OADs combined with other drugs. Clinical factors and laboratory essay results of the 22389 patients were analyzed with Logistic regression analysis. Restricted cubic spline(RCS) inbedded in logistic regression was used to examine possible nonlinear associations of duration of T2DM with increased risks of vascular complications. To document the chracteristics of long survivors of T2DM, this study also retrieved 157 survivors with over 40 years of T2DM from a total of 582,773 patients with T2DM enrolled in the CNHSS from 2009 to 2012. Two matched case control studies were organized with the long survivors of T2DM as the cases,separately matched on the survey day, sex and survey hospital(the first case-control study) and on age, sex and survey hospital(the second case-control study). Conditional logistic regression analysis was performed to obtain odds ratios(ORs) while controlling for other confounders.Results Among the 22389 patients with T2DM, the prevalences of diabetic retinopathy(DR) in patients with < 5 years, 5~10 years and > 10 years of duration of T2DM were 4.9%, 10.8% and 18.4%, respectively. Diabetic nephropathy(DN) had developed in 2.6%, 6.4% and 13.5%, respectively among patients with < 5 years, 5-10 years and >10 years of duration of T2DM. In the same manner, the prevalences of coronary heart disease(CHD) in the three groups with different durations of T2DM were 7.1%, 12.9% and 21.2% and those prevalences of stroke in the three groups were 2.7%, 5.5% and 9.1%, respectively. After adjusting for age, sex, hospital level and other metabolic factors in logistic regression analysis, patients with 5~10 years and >10 years of duration of T2DM were more likely than those who had < 5 years of T2DM to have developed DR(OR of 5~10 years: 2.02, 95%CI: 1.79-2.27; OR of >10 years: 3.07, 95%CI: 2.72-3.47). Patients with 5~10 years and >10 years of duration of T2DM were also more likely than those who had < 5 years of T2DM to have DN(OR of 5~10 years: 2.25, 95%CI: 1.93-2.64; OR of >10 years: 4.36, 95%CI: 3.75-5.07). For macrovascular diseases, patients with 5~10 years and >10 years of duration of T2DM had 1.49(1.34-1.66) and 2.09(1.87-2.34) folds likelihoods of those who had < 5 years of T2DM to have developed CHD. Similarly, patients with 5~10 years and >10 years of duration of T2DM had 1.59(1.33-1.89) and 1.98(1.66-2.37) folds likelihood of those who had < 5 years of T2DM to have developed stroke. The group with an extreme long duration of T2DM had a mean age of 75(SD: 9.6) years and their T2DM was diagnosed at a mean age of 32 years with a median duration of T2DM as long as 41 years. In both case control studies, these long survivors were associated with increased risks of hyperglycemia and CHD(OR: 6.31, 95%CI: 1.89-21.09; 2.18, 1.01-4.70, respectively). However, these long survivors were not associated with higher likelihoods of abnormal lipids, DN and stroke than those with a shorter duration of T2DM.Conclusion Our study found that diabetes duration was an independent risk factor for macro- and micro-vascular complications. On the other hand, some patients survived an extreme long duration of T2DM and this group of Chinese patients with an extremely long duration of T2DM also had increased risks of hyperglycemia and CHD. Further studies are needed to investigate whether non-increased risk of DN contributed to their survival of T2DM.