People with impaired glucose tolerance (IGT) have increased risk of mortality
and a high risk of progression to diabetes, but the extent that the excess mortality
is associated with IGT per se or is the result of subsequent diabetes is unclear.
RESEARCH DESIGN AND METHODS
We compared mortality before and after the development of diabetes among
542 persons with IGT initially who participated in a 6-year lifestyle diabetes prevention trial and were followed-up from 1986 to 2009.
RESULTS
During the 23-year follow-up, 174 (32.1%) died, with an overall death rate of
15.9/1,000 person-years. The majority of deaths (74.7%; 130 of 174) occurred
after progression to type 2 diabetes, with age-adjusted death rates of
11.1/1,000 person-years (95% CI 8.2–12.0) before and 19.4/1,000 person-years
(95% CI 11.9–23.3) after the development of type 2 diabetes. The cumulative
mortality was 37.8% (95% CI 33.1–42.2%) in participants who developed type 2
diabetes during first 10 years of follow-up, 28.6% (95% CI 21.6–35.0%) in those
who progressed to type 2 diabetes in 10–20 years, and 13.9% (95% CI 7.0–20.3%)
in those who did not develop to type 2 diabetes within 20 years. Time-dependent
multivariate Cox proportional hazards analyses, with adjustment for baseline age,
sex, intervention, and other potential confounding risk factors, showed that the
development of type 2 diabetes was associated with a 73% higher risk of death
(hazard ratio 1.73 [95% CI 1.18–2.52]).
CONCLUSIONS
As elsewhere, IGT is associated with increased risk of mortality in China, but much
of this excess risk is attributable to the development of type 2 diabetes.