Menstrual and reproductive factors and endometrial cancer risk: Results from a population‐based case‐control study in urban Shanghai

Abstract

The purpose of our study was to evaluate the association of menstrual and reproductive factors with the risk of endometrial cancer. In a population-based case-control study conducted in urban Shanghai, in-person interviews were completed for 833 women aged 30 -69 years and an equal number of controls frequency-matched to cases by age. All cases were newly diagnosed with endometrial cancer between January 1, 1997 and December 31, 2001. The unconditional logistic regression model was employed to derive the adjusted odds ratios (ORs) of endometrial cancer and 95% confidence intervals (CIs) in relation to menstrual and reproductive factors. Earlier menarche age, particularly among premenopausal women, and later menopausal age were associated with an elevated risk of endometrial cancer. A clear dose-response relation between endometrial cancer risk and years of menstruation was observed (p for trend < 0.01). Compared to women ever having a pregnancy and women ever having had a live birth, respectively, nulligravity and nulliparity were both associated with a more than one-fold elevated risk of endometrial cancer. Both completed (OR ‫؍‬ 3.02, 95% CI 1.10 -8.32 for women never having a complete pregnancy) and incomplete pregnancy (OR ‫؍‬ 0.69, 95%CI 0.55-0.87) conferred a protective effect against endometrial cancer, and the protective effect appeared to increase with total number of pregnancies (p for trend ‫؍‬ 0.01). The effect of pregnancy on endometrial cancer remained unchanged with increasing time since the last pregnancy. Stillbirth and age at first pregnancy was unrelated to endometrial cancer risk. Our study suggests that prolonged menstruation was related to an increased risk of endometrial cancer while pregnancy, including induced abortion, reduced the risk of endometrial cancer. © 2003 Wiley-Liss, Inc. Key words: endometrial cancer; menstruation; pregnancy; abortion; case-control studiesChinese women historically have a lower risk of endometrial cancer compared to their counterparts in the United States and other western countries. However, the incidence of endometrial cancer in Shanghai women has substantially increased over the past 2 decades. The age-adjusted endometrial cancer incidence rate increased 76% from 2.5/100,000 in 1972-74 to 4.4/100,000 in 1994, becoming 1 of the 10 most common cancers among Shanghai women. 1 The increase was more pronounced among older women, with 132.1% and 2.08% for women 55-64 and 35-44, respectively, for the same time period. Menstrual and reproductive factors, such as age at menarche, age at menopause, nulligravity and live birth, have been associated with the risk of endometrial cancer in many previous studies, including a study conducted among Chinese women. 2-5 Prolonged estrogen stimulation without the protection of progesterone has been suggested as the possible mechanism for the association of menstrual and reproductive factors with the risk of endometrial cancer. 6 -8 However, results from earlier studies were not entirely consistent, particularly regarding the e...

Reproductive risk factors for endometrial cancer among Polish women

“…Our investigation also enabled evaluation of effects of shortterm pregnancies, including spontaneous and induced abortions. Although several studies have noted either reduced (Parazzini et al, 1998;Parslov et al, 2000) or increased (Shu et al, 1991;McPherson et al, 1996) risks, we found no substantial relationship with spontaneous abortions, in line with most other investigations (Brinton et al, 1992;Xu et al, 2004;Wernli et al, 2006). Previous studies assessing the effects of induced abortion on endometrial cancer risk have been inconsistent, possibly reflecting small numbers of exposed women.…”

“…This factor has not generally been regarded as a predictor of endometrial cancer risk (Pettersson et al, 1986;Lesko et al, 1991;Brinton et al, 1992;Parazzini et al, 1998;Xu et al, 2004), despite a number of studies that have demonstrated relatively strong associations (Kvale et al, 1988;Parslov et al, 2000;Hinkula et al, 2002;Wernli et al, 2006). Although it is widely accepted that multiparity may reduce endometrial cancer risk through changes in hormonal profiles, including lowered estradiol and increased sex hormone binding globulin levels (Chubak et al, 2004), underlying mechanisms for reduced risks associated with delayed ages at a first birth are less clear.…”

Smoking, Earlier Menarche and Low Parity as Independent Risk Factors for Gynecologic Cancers in Japanese: A Case-Control Study

“…For cervical cancer, the decrease in risk with increasing age at first marriage was found. Among them, similarities in reproductive risk factors between cancers of the endometrium and ovary have been observed in previous epidemiologic studies from Western countries (Baron et al 1986;Brinton et al 1992;Whittemore et al 1992;Adami et al 1994;Kelsey et al 1994;Hankinson et al 1995;McPherson et al 1996;Lambe et al 1999;Greggi et al 2000;Persson 2000;Riman et al 2002;Xu et al 2004;Zhang et al 2004). Several Japanese studies also support such similarities; Hirose and Okamura showed a decrease in endometrial cancer risk associated with increasing parity number (Hirose et al 1999;Okamura et al 2006), and Mori et al demonstrated the association with parity number in ovarian cancer (Mori et al 1998).…”

Improving the existing diagnostic strategy by accounting for characteristics of the women in the diagnostic work up for postmenopausal bleeding

“…This variability has been associated with individual characteristics of the women including age, time since onset of menopause, obesity, hypertension, diabetes mellitus and reproductive factors. [5][6][7][8][9][10] However, guidelines currently used are mainly based on endometrial thickness only and do not systematically take these additional characteristics into account. 3 Inclusion of these individual characteristics may allow for a more refined differentiation of women with the same endometrial thickness.…”