The prevalence of type 2 diabetes has increased in the early part of the 20th century, particularly in developing countries. There is now evidence that the prevalence also continues to increase in developed countries, including the United States. However, it is unknown whether this increase is due to a rise in the incidence of diabetes or to decreasing diabetic mortality or both.
Participants in the San Antonio Heart Study, who were nondiabetic at baseline and who returned for a 7- to 8-year follow-up examination, were examined for secular trends in the incidence of type 2 diabetes. Risk factors for diabetes, such as obesity, were also examined. Patients were enrolled in the San Antonio Heart Study from 1979 to 1988 and 7- to 8-year incidence of diabetes was determined from 1987 to 1996.
A significant secular trend in the 7- to 8-year incidence of type 2 diabetes was observed in Mexican Americans (5.7% for participants enrolled in 1979 to 15.7% for participants enrolled in 1988). In non-Hispanic whites, the incidence increased from 2.6% for participants enrolled in 1980 to 9.4% for participants enrolled in 1988 (P=.07) . After adjusting for age and sex, the secular trend remained significant in Mexican Americans and borderline significant in non-Hispanic whites. This indicates that between 1987 and 1996 the 7- to 8-year incidence of type 2 diabetes approximately tripled in both ethnic groups. The overall secular trend also remained significant after adjusting for additional risk factors for diabetes, such as obesity. A rising secular trend in obesity was also observed.
There has been a significant increasing secular trend in the incidence of type 2 diabetes in Mexican Americans and a borderline significant trend in non-Hispanic whites participating in the San Antonio Heart Study. Unlike other cardiovascular risk factors such as lipid levels, cigarette smoking, and blood pressure, which are either declining or under progressively better medical management and control, and unlike cardiovascular mortality, which is also declining, obesity and type 2 diabetes are exhibiting increasing trends. Thus, obesity and diabetes could easily become the preeminent US public health problem.