RISK OF UTERINE LEIOMYOMATA AMONG PREMENOPAUSAL WOMEN IN RELATION TO BODY-SIZE AND CIGARETTE-SMOKING

To investigate whether factors influencing ovarian function affect ris k of uterine leiomyomata, we examined prospectively the association of new diagnoses confirmed by ultrasound or hysterectomy with body mass index, weight change, height, and cigarette smoking among 94,095 preme nopausal women with intact uteri, who were ages 25-42 years at the sta rt of follow-up in 1989. We assessed body mass index and cigarette smo king from responses on the study questionnaire completed just before d iagnosis. During 322,775 person-years, 2,967 new cases of uterine leio myomata confirmed by ultrasound or hysterectomy were reported. Risk am ong all cases confirmed by ultrasound or hysterectomy increased with i ncreasing adult body mass index. The multivariate relative risks (RR) and 95% confidence intervals (CI) according to body mass index categor ies of <20.0, 20.0-21.9, 22.0-23.9, 24.0-25.9, 26.0-27.9, 28.0-29.9, a nd greater than or equal to 30.0 were 0.90 (95% CI = 0.79-1.03), 1.00 (referent), 1.08 (95% CI = 0.97-1.21), 1.16 (95% CI = 1.03-1.31), 1.21 (95% CI = 1.05-1.40), 1.36 (95% CI = 1.16-1.59), and 1.23 (95% CI = 1 .09-1.39), respectively. The RRs for hysterectomy-confirmed cases gene rally were higher. Similarly, risk was positively associated with weig ht gain since age 18 years. Body mass index at age 18 years, height, a nd cigarette smoking were unrelated to risk of uterine leiomyomata. El evated adult body mass index is associated with a modest increased ris k of uterine leiomyomata among premenopausal women.