Smoking May Increase Risk Of Diabetes

The surprising finding emerged when researchers examined therelationship between smoking and diabetes among participants in a majornational study, the Insulin Resistance Atherosclerosis Study (IRAS).They compared the incidence of diabetes after five years among smokersand those who had never smoked.

Twenty-five percent of the participants who smoked and did nothave diabetes when the study began had developed diabetes by thefive-year follow-up, compared to 14 percent of the participants who hadnever smoked, according to Capri G. Foy, Ph.D., and her colleagues atthe national IRAS coordinating center at the School of Medicine, partof Wake Forest University Baptist Medical Center.

Reporting in the journal Diabetes Care, the researchers foundthat when the analyses were adjusted to account for other diabetes riskfactors, "smokers still exhibited significantly increased incidence ofdiabetes compared to people who had never smoked," Foy said. "Thesefindings suggest another poor health outcome associated withcigarettes, supporting current surgeon general's warnings againstcigarette smoking."

Smoking has long been associated with heart disease, as isdiabetes, and Foy noted that diabetes and heart disease share many riskfactors.

IRAS focused on a prediabetic condition called insulinresistance, in which increasing amounts of insulin are needed to digestthe same amount of glucose, the principal product of the metabolism ofcarbohydrates.

Other Wake Forest IRAS investigators had reported in theAmerican Heart Association Journal Circulation back in 1996 thatinsulin resistance is associated with substantially increasedatherosclerosis, which involves the buildup of fatty substances,cholesterol, and other substances in the walls of the arteries. Thestudy found that increased thickness of the walls of the carotid arteryin the neck suggested that insulin resistance might be an independentrisk factor for heart disease.

Since that report, IRAS investigators have been asking otherresearch questions, based on extensive examinations at the start of thestudy -- two four-hour visits scheduled one week apart that directlymeasured indicators such as glucose tolerance, body mass index (BMI),cholesterol and high blood pressure, comparing those results with afollow-up examination five years later. The initial examinations alsoincluded questions about smoking.

Foy said that another strength of IRAS was that it had roughlyequal numbers of men and women and roughly equal numbers ofAfrican-Americans, Hispanics and whites recruited from Los Angeles andOakland, Calif., San Antonio, Texas and the San Luis Valley area ofColorado.