Age at menarche, probability of ovulation and breast cancer risk

Abstract

An analysis is undertaken of the frequency of ovulation in 17 groups of women aged 15 to 19 who had been the subjects of other studies. A urine specimen of at least 8 h accumulation had been provided on the 20th or 21st day of a menstrual cycle by 681 women. Analysis is restricted to 431 specimens which had been collected between 11 and 3 days prior to the onset of the subsequent menstrual period. A pregnanediol concentration of less than 1 mg per litre in such a specimen was taken as evidence that the cycle was anovular. The probability of a cycle being anovular was inversely and significantly related to the number of years since menarche, and, with years since menarche held constant, was positively but not significantly associated with age at menarche. This observation indicates that women with early menarche do not have a longer duration of exposure to anovular cycles than do those whose menarche is delayed, and that variation in the duration of exposure to post-menarcheal anovular cycles does not explain the association of breast cancer risk with early age at menarche. The 17 groups of women were classified into four categories according to ethnic origin and breast cancer incidence in the populations from which they derived. Anovular cycles were not more common in the high-risk groups; indeed, the two centers in the lowest risk category had the highest proportion of anovular cycles.

The effects of moderate physical activity on menstrual cycle patterns in adolescence: Implications for breast cancer prevention

“…The effects of age at menarche and gynaecologic age on the probability of anovulation in our study group are consistent with those reported by others (MacMahon et al, 1982;Apter & Vihko, 1985). Girls who participated in moderate physical activity, averaging more than 600 kcal of energy expenditure in such activity per week, were significantly more likely than less active girls to be classified as anovular.…”

“…Young women with menarche before age 12 have a risk of breast cancer that is two times greater than that of women whose age at menarche is 13 or older (Pike et al, 1981). Teenage girls from populations with low breast cancer rates have both later menarche and a lower frequency of ovulatory cycles for a fixed number of years since menarche, than do girls from high risk populations (MacMahon et al, 1982). In particular, Japanese women have significantly lower rates of breast cancer than US women and this is explained, in part, by their later age at menarche and lower body weight .…”

Reproductive Factors in Breast Cancer Epidemiology

“…However, Wallace et al (39) observed that women with early menarche established a pattern of regular cycle intervals more promptly than women with late menarche, and early onset of ovulatory cycles has been observed in women with early menarche (40)(41)(42). In a case-control study (43), it was found that breast cancer patients established regular cycles significantly earlier than controls.…”

The woman at increased risk for breast cancer: evaluation and management strategies

“…[17][18][19][20][21] Menarche prior to age 14 years increases breast cancer risk by a factor of 1.1 to 1.9 compared with menarche after age 14 years. 17,18 Similarly, late onset of menopause also increases breast cancer risk, with women who experience menopause prior to age 45 years having about half the incidence of breast cancer of women who experience menopause after age 55 years. 19,20 It appears that the longer the duration of menstrual life, the greater the incidence of breast cancer.…”