U.S. Diabetes-Free Life Expectancy on the Decline



Americans are living longer – but not healthier – lives, researchers have found.

While average life expectancy is now higher than ever, the number of years Americans can expect to live without type 2 diabetes is decreasing. A prolonged period of morbidity is more likely to characterize people’s later years now than it was in the 1980s.

The difference was driven by a marked increase in the number of Americans who are obese, according to findings published Sept. 23 by Solveig A. Cunningham, Ph.D., an epidemiologist at Emory University in Atlanta, and colleagues. More than one-third of American adults now have a body-mass index of 30 kg/m2 or higher.

"All of the observed reductions in diabetes-free life expectancy at the population level were actually due to increases in diabetes only among obese individuals," Dr. Cunningham and colleagues reported (Diabetes Care 2011;34:2225-30 [doi:10.2337/dc11-0462]).

The fact that obese individuals would be more likely to be diagnosed with diabetes in the 2000s than in the 1980s, they wrote, may be because obese adults were 3.4% heavier in the latter period, or it may reflect better diagnosis of diabetes in this population group, the researchers hypothesized. Another possible explanation "is that diabetes risks are higher with younger age of obesity onset; indeed, the prevalence of obesity has tripled among children since the 1970s."

For other weight groups, including people classified as overweight (BMI, 25-30), the diabetes-free life expectancy actually improved from the 1980s to the 2000s. However, this was largely thanks to overall mortality decreasing. Life expectancy as a whole was 70.6 years for men and 77.4 years for women in the 1980s, and had increased to 74.3 for men and 79 years for women by 2000-2004.

The proportion of obese individuals had grown enough in the same time period to alter estimates of disease-free life expectancy for the population as a whole, the investigators found.

All together, diabetes-free life expectancy for an 18-year-old U.S. man was 1.7 years longer in the 1980s than it was during 2000-2004; for a woman, it was 1.5 years longer in the 1980s. The proportion of 18-year-olds who would be diagnosed with diabetes in their lifetimes increased by almost 50% among women between 1980-1989 and 2000-2004, and almost doubled among men, Dr. Cunningham and colleagues found.

Obese men lost an average of 5.6 years of diabetes-free life between the 1980s and the early 2000s, whereas women lost 2.5 years in the same interval. "In 2000-2004, obese 18-year-old men and women could expect to live 13.7 and 19.1 fewer years without diabetes, respectively, compared with normal/underweight 18-year-old men and women," the investigators wrote.

For their research, Dr. Cunningham and colleagues examined data from the National Vital Statistics System and the National Health Interview Survey, which collects self-reported health information from the noninstitutionalized, nonmilitary population.

The 1980-1989 NHIS surveys analyzed by Dr. Cunningham and colleagues contained responses from 143,765 adults (507 diagnosed diabetic in the previous year), and the 2000-2004 period surveys contained responses from 150,718 (1,366 diagnosed diabetic in the previous year).

Dr. Cunningham and colleagues examined diabetes and obesity incidence in the survey population in the context of changes in national mortality rates and population aging between the time periods.

Limitations of the study included its reliance on self-reported information about diabetes diagnosis, weight, and height, which is susceptible to bias. However, the investigators wrote that "NHIS data are collected via rigorous in-person interviews, and the differences in reported and measured BMI are not large and do not affect health risk estimates, including those associated with diabetes."

The researchers concluded that their results "suggest that in the face of budgetary or logistic constraints, new efforts to prevent diabetes can have the greatest impact among obese individuals," as all other groups were shown to have improved diabetes-free life expectancy over the decades studied.

Dr. Cunningham and colleagues reported no conflicts of interest.

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