Non-diabetes status after diagnosis of impaired glucose tolerance and risk of long-term death and vascular complications: A post hoc analysis of the Da Qing Diabetes Prevention Outcome Study

Background The association between years of non-diabetes status after diagnosis of impaired glucose tolerance (IGT) and the risk of long-term death and cardiovascular outcomes needed to be clarified. Methods and findings In this post hoc analysis, we included 540 individuals with IGT who participated in the original Da Qing Diabetes Prevention Study (DQDPS). In the DQDPS, all participants were diagnosed with IGT by a 75 g oral glucose tolerance test and randomized to intervention or control groups with a 6-year lifestyle intervention trial. After the completion of the trial, death, cardiovascular events, and microvascular complications were monitored over a 30-year follow-up. In this post hoc analysis, the Cox analysis assessed the extended risk of these outcomes in individuals who either remained non-diabetes status or progressed to diabetes at the end of 2, 4, and 6 years after diagnosis of IGT. In all participants, the difference in the cumulative incidence rate of the outcomes between the diabetes and non-diabetes group gradually increased over 30 years. Compared with the diabetes group, a significantly lower risk of all-cause death (hazard ratio [HR]: 0.74; 95% confidence interval [CI]: 0.57 to 0.97, p = 0.026), cardiovascular events (HR: 0.63; 95% CI: 0.49 to 0.82, p < 0.001), and microvascular complications (HR: 0.62; 95% CI: 0.45 to 0.86, p = 0.004) first emerged in individuals who remained non-diabetes at the 4 years visit, whereas the significant risk reduction in cardiovascular death was first observed at the end of 6 years (HR: 0.56; 95% CI: 0.39 to 0.81, p = 0.002) after adjustment for age, sex, smoking status, BMI, systolic blood pressure, blood glucose, total cholesterol, intervention, and medications (including insulin plus oral hypoglycaemics, antihypertensives, and lipid-lowering agents). The results in the original intervention group alone were similar to the whole group. The main limitations of our study are the limited number of participants and the sole ethnicity of the Chinese population. Conclusions In this study, we observed that maintaining several years of non-diabetes status after IGT diagnosis was associated with a significant reduction in long-term risk of death and vascular complications, and for most of these outcomes, maintaining at least 4 years of non-diabetes status may be needed to achieve a significant risk reduction.