Smokers with IDDM experience excess morbidity. The Colorado IDDM Registry

OBJECTIVE--To determine whether there is an association between smoking and the self-reported morbidity of people with IDDM and to evaluate the nature of a possible interaction between smoking and IDDM in increasing the risk of morbidity among smokers with IDDM. RESEARCH DESIGN AND METHODS--Subjects were non-Hispanic whites aged 18-28 yr who participated in the Colorado IDDM Registry Follow-up Survey (case subjects, n = 24) or the 1985 NHIS (control subjects, n = 5876). Assessments of self-reported morbidity included any hospitalization in the past year; bed days, sick days, and limited-activity days in the past 2 wk; and ratings of poor health. The criteria outlined by Saracci were used to determine whether smoking was associated with greater morbidity among IDDM case compared to control subjects (smoking by IDDM interaction). RESULTS--Age- and sex-adjusted ORs, estimated from logistic regression, showed that people with IDDM reported excess morbidity compared with control subjects, regardless of smoking status. Smokers with IDDM reported morbidity 3-10 times as often as nonsmoking control subjects and were 2-3 times more likely to report morbidity than nonsmokers with IDDM. The smoking by IDDM interaction was more than multiplicative for all morbidity measures. Fifty to 75% of excess morbidity in young smokers with IDDM over simple additive effects was related to the interaction between smoking and IDDM. CONCLUSIONS--There was excess reported morbidity among people with IDDM who smoked, greater than that expected from the combined effects of smoking and IDDM. Smoking cessation in young people with IDDM may alleviate some of this excess, but more study is needed to determine whether smoking serves as an indicator of poor IDDM care practices or has a physiological impact that compounds the morbidity experienced by people with IDDM.