[A case-control study of ovarian cancer to identify its risk factors].

To analyze the association between the potential risk factors and ovarian cancer, we conducted a case-control study from October, 1994 to January, 1996 in northern Kyushu. We interviewed 78 patients whose ovarian cancer was histologically confirmed, and 346 controls, selected from women at mass screening, who had not ever suffered from a cancer or an ovarian disorder. An odds ratio (OR) and its 95% confidence interval (95% CI) were estimated by the conditional logistic regression method. As a result, it was found that the risk was significantly increased for a family history of ovarian cancer in a mother or a sister (OR = 2.85, 95% CI 1.01-8.08), for heavier maximum body weight in the past (trend, OR = 1.31, 95% CI 1.06-1.63), and for larger maximum body mass index (trend, OR = 1.30, 95% CI 1.06-1.60). Conversely, the risk was significantly decreased with the number of parities (trend, OR = 0.57, 95% CI 0.39-0.83), and with experience in having ever taken oral contraceptive pills (OR could not be calculated, p < 0.05). The positive relationship of maximum body weight or maximum body mass index to the ovarian cancer risk may in part explain the recent increase in the incidence of ovarian cancer in Japan.