RAND finds cases of undiagnosed diabetes drop sharply

The number of men in the United States with undiagnosed diabetes has declined sharply over the past 25 years, with Hispanics and African-Americans no longer more likely than whites to unknowingly have the disease, according to a RAND Corporation study issued today.

Study author James P. Smith found that in 1999-2002 about 20 percent of American men who had diabetes did not know they had the disease, in contrast to 25 years ago when about half of the men with diabetes were undiagnosed.

Ethnic disparities among those with undiagnosed diabetes essentially disappeared during the same period, a sign that diabetes programs targeting minority groups have encouraged more people to get tested, according to the study appearing in the August edition of the Proceedings of the National Academy of Sciences.

“While undiagnosed diabetes remains a significant problem, we’ve done an excellent job of eliminating the disproportionate amount of undiagnosed disease among African-Americans and Hispanics,” said James P. Smith, the study’s sole author and corporate chair of labor market and demographic studies at RAND, a nonprofit research organization.

On a less positive note, Smith found that while disparities in undiagnosed diabetes disappeared over the past 25 years, new disparities have developed based upon education levels. Less educated American males are now less likely to have their diabetes diagnosed than those men with more schooling.

“If we only target disparities by race and ethnicity, we run the risk of missing other equally important health disparities that affect those least able to deal with them,” Smith said.

The study also found the rate of growth of diabetes prevalence is not as high or as dramatic as often projected. Smith found that during the period studied, the proportion of men diagnosed with diabetes jumped from about 3 percent to 7 percent - a more than doubling of the prevalence rate. However, when undiagnosed cases were considered as well, diabetes prevalence rose overall from 6 percent to 9 percent - an increase of only 50 percent.

“Diabetes is one of the major health challenges faced across the United States, but these findings suggest that the prevalence of the disease is not growing as rapidly as often claimed,” Smith said.

The study examined reasons for the rising rate of diabetes over time. The three most important reasons by far were increases in excessive weight, the transmission of diabetes from parents to children as the disease spreads, and the decline in undiagnosed diabetes. In contrast, rising levels of education actually served to reduce the prevalence of the disease.

Smith examined information from several waves of the federal National Health and Nutrition Examination Surveys conducted periodically from 1976 to 2002. The survey collects information from a nationally representative sample of adults through personal interviews, physical exams and laboratory tests. Blood tests conducted as a part of the survey allow researchers to measure undiagnosed diabetes.