Background: Recent studies indicate that the prevalence of type 2 diabetes mellitus is increasing in the United States; less is known about trends in the incidence of type 2 diabetes mellitus.
Methods and results: Participants free of diabetes mellitus (n=3104; mean age 47 years; 1587 women) from the Framingham Offspring Study who attended a routine examination in the 1970s, 1980s, or 1990s were followed up for the 8-year incidence of diabetes mellitus. Diabetes was defined as a fasting plasma glucose > or = 7.0 mmol/L or treatment with either insulin or a hypoglycemic agent. Pooled logistic regression was used to compare diabetes incidence across decades for participants between 40 and 55 years of age in each decade. The age-adjusted 8-year incidence rate of diabetes was 2.0%, 3.0%, and 3.7% among women and 2.7%, 3.6%, and 5.8% among men in the 1970s, 1980s, and 1990s, respectively. Compared with the 1970s, the age- and sex-adjusted odds ratio (OR) for diabetes was 1.40 (95% confidence interval [CI], 0.89 to 2.22) in the 1980s and 2.05 (95% CI, 1.33 to 3.14) in the 1990s (P for trend=0.0006). Among women, the OR was 1.50 (95% CI, 0.75 to 2.98) in the 1980s and 1.84 (95% CI, 0.95 to 3.55) in the 1990s (P for trend=0.07) compared with the 1970s, whereas among men, the OR was 1.33 (95% CI, 0.72 to 2.47) in the 1980s and 2.21 (95% CI, 1.25 to 3.90) in the 1990s (P for trend=0.003). Most of the increase in absolute incidence of diabetes occurred in individuals with body mass index > or = 30 kg/m2 (P for trend=0.03).
Conclusions: In the present community-based sample of middle-aged adults, we observed a doubling in the incidence of type 2 diabetes over the last 30 years. Careful surveillance of changes in diabetes incidence may be necessary if current trends of excess adiposity continue.