To investigate whether obesity and hormone therapy (HT) are associated with ovarian cancer risk among women in the California Teachers Study cohort.
Of 56,091 women age ≥45 years, 277 developed epithelial ovarian cancer between 1995 and 2007. Multivariate Cox regression was performed.
Among women who never used HT, greater adult weight gain, waist circumference and waist-to-height ratio, but not adult BMI, increased risk of ovarian cancer. Compared to women who never used HT and had a stable adult weight, risk of ovarian cancer was increased in women who gained ≥40 lb (relative risk (RR) 1.8, 95% confidence interval (CI): 1.0–3.0) or used HT for >5 years (RR 2.3 95% CI: 1.3–4.1). Having both exposures (RR 1.9, 95% CI: 0.99–3.5), however, did not increase risk more than having either alone. Results were similar for waist circumference and weight-to-height ratio; however, differences across HT groups were not statistically significant.
This study suggests that abdominal adiposity and weight gain, but not overall obesity, increase ovarian cancer risk and that there may be a threshold level beyond which additional hormones, whether exogenous or endogenous, do not result in additional elevation in risk. However, large pooled analyses are needed to confirm these findings.