Department of Biostatistics, Institute for Basic Medical Sciences, University of Oslo, PO Box 1122, N-0317 Oslo, Blindern, Norway. anette.hjartaker@medisin.uio.no
Overweight and obesity increase the risk of numerous chronic diseases, including several forms of cancer. However, the association between excess body weight and all-cause mortality among young and middle-aged women is incompletely known, and the impact of menopausal status on the association has hardly been investigated. We studied prospectively a cohort comprising a population sample of 102,446 women from Norway and Sweden aged 30-50 years when they answered an extensive questionnaire in 1991/1992. During follow-up through year 2000, 1187 women in the cohort died. We used Cox proportional hazard models to estimate multivariate Hazard rate ratios (HRR) with 95% confidence intervals (CI) of death in relation to body mass index (BMI, weight (kg)/height (m(2))) at start of follow-up. Both in age-adjusted models and in models adjusting for several variables (including smoking and physical activity) mortality increased with increasing BMI among premenopausal women, whereas a U-shaped relationship was seen among the postmenopausal women. Among premenopausal women obesity (BMI 30.0) doubled the mortality (HRR = 2.2, 95% CI: 1.7-3.0) when compared to women of normal weight (BMI 18.5-24.9), whilst the association was modest after menopause. Although we had limited power to analyze women who were underweight (BMI