Relation between obesity and breast cancer in young women

This study was conducted to assess the relation between body size and risk of breast cancer among young women. A case-control study was conducted amon g women aged 21-45 years living in three counties in Washington State. Case s were women born after 1944 with invasive or in situ breast cancer that wa s diagnosed between January 1, 1983, and April 30, 1990. Controls were sele cted using random digit dialing and were frequency-matched to cases on the basis of age and county of residence. interviews took place between 1986 an d 1992, Body size was evaluated using indices from several different time p eriods. After adjustment for confounders, a decreased risk of breast cancer was found for women in the highest quintile of body mass index (weight (kg )/height (m)(2)) as compared with the lowest quintile (for maximum lifetime body mass index, odds ratio = 0.69, 95% confidence interval (Cl) 0.51-0.94 ). Age modified the relation between body size and risk of breast cancer. T he odds ratio for women in the highest quintile of maximum body mass index who were aged 21-35 years was 0.29 (95% CI 0,16-0.55), as compared with an odds ratio of 1.5 for women aged 36-45 years (95% CI 0.9-2.5) (p for intera ction = 0.003). This study supports prior research showing a decreased risk of breast cancer associated with increased body size among premenopausal o r young women. More detailed analysis in this study found a strong effect t hat was limited to the youngest age group (less than or equal to 35 years).