Prior studies have reported an increased risk of diabetes related to polychlorinated biphenyl (PCB) exposure. No study has yet investigated whether polybrominated biphenyls (PBBs), which are similar in chemical structure, increase the incidence of diabetes.
The Michigan PBB cohort was established in 1976 and surveyed again in 1991–1993 and in 2001. PBB and PCB serum levels were measured from blood collected at enrollment. To determine the incidence of adult-onset diabetes, we analyzed cohort members without diabetes at enrollment, ages 20 years and older, with known PBB and PCB levels, who participated in at least 1 follow-up survey (n = 1384). Using Poisson regression, we determined the incidence density ratio (IDR) of diabetes for different serum levels of PBB and PCB, controlling for age, body mass index, smoking, and alcohol consumption at enrollment.
Analyzing 25 years of follow-up data, we did not find that higher PBB serum levels were a risk factor for the incidence of diabetes mellitus. However, in women, but not in men, higher PCB serum levels were associated with increased incidence of diabetes (IDR = 2.33; 95% confidence interval = 1.25–4.34 in the highest PCB group compared with the lowest). In both men and women, overweight and obesity increased the diabetes incidence.
We found no association between PBB serum levels and diabetes incidence. In women, there was a positive linear association of diabetes incidence with PCB serum levels at enrollment. This finding is in agreement with 2 prior studies indicating a higher relative risk of diabetes in PCB-exposed women.
From the *Department of Epidemiology, College of Human Medicine, Michigan State University, East Lansing, Michigan; †Division of Environmental and Occupational Epidemiology, Michigan Department of Community Health, Lansing, Michigan; and ‡Department of Epidemiology and Biostatistics, Arnold School of Public Health, Columbia, South Carolina.
Submitted 17 February 2005; accepted 30 December 2005.
Supported by grants U37/CCU500392 from the Centers of Disease Control.
Editors’ Note: A commentary on this article appears on page 350.
Correspondence: Wilfried Karmaus, Department of Epidemiology and Biostatistics, Norman J. Arnold School of Public Health, University of South Carolina, 800 Sumter Street, Columbia, SC 29208-0001. E-mail: firstname.lastname@example.org.