People with impaired glucose tolerance may significantly lower their risk of cardiovascular disease (CVD) and microvascular disease by delaying the onset of type 2 diabetes by six years or more, or by returning to a normal level of glucose tolerance altogether, according to a study presented at the American Diabetes Association annual conference.

The study, Early Progression to Diabetes or Regression to Normal Glucose Tolerance Among People with Impaired Glucose Tolerance Affects Long-Term Outcomes: Thirty-Year Follow-Up of Da Qing Diabetes Prevention Study,”  found that people with impaired glucose tolerance have a much higher likelihood of developing and a higher risk of developing CVD and microvascular disease compared to those with normal glucose tolerance.

The Da Qing Diabetes Prevention Study (DQDPS) showed that 90% of impaired glucose tolerance participants in the non-intervention group had developed diabetes over a 20-year period, however, the extent of the increased risk that can be directly attributed to the onset of diabetes has been unclear.

To assess this risk, researchers conducted a secondary analysis of the DQDPS. The original study enrolled 540 adults in China with impaired glucose tolerance who were randomly assigned to participate in a lifestyle intervention (diet or exercise, or both) for six years. At the end of the study, participants were evaluated to determine who had developed diabetes, regressed to normal glucose tolerance or remained with impaired glucose tolerance.

In 2016, 30 years after the start of the study, researchers conducted a follow-up study to assess the number and proportion of participants who had developed CVD (defined as non-fatal or fatal stroke, myocardial infarction or heart failure) and microvascular disease (defined as the first occurrence of severe retinopathy, nephropathy, neuropathy).

The results of the analysis found among the 252 adults who had developed diabetes, 65.6% developed CVD and 44.3% developed microvascular disease; among the 114 who remained with IGT, 50.6% developed CVD and 31.2% developed microvascular disease; and among the 174 who reverted to normal glucose tolerance, 46.1% developed CVD and 23.1% developed microvascular disease. Overall, those with impaired glucose tolerance who developed diabetes had a 69% higher incidence of CVD and a 150% higher incidence of microvascular disease.

Delaying the onset of diabetes

As a result, researchers concluded that delaying the onset of diabetes in people with impaired glucose tolerance by six years or more resulted in lower rates of complications and reduces the development of both CVD and microvascular disease.

“We know people with impaired glucose tolerance are at high risk for developing diabetes and other complications,” said study author Guangwei Li, MD, honorary director of the International Medical Center at the China-Japan Friendship Hospital; and director of the center of endocrinology and cardiovascular disease at the National Center of Cardiology at Fuwai Hospital, Chinese Academy of Medical Sciences. “Our study clearly shows that reversing or delaying the onset of diabetes in people with IGT by six years or more significantly lowers their risk for developing long-term complications such as CVD and microvascular disease. Essentially, the longer progression to diabetes can be delayed, the fewer the complications.”