The effect of wartime conditions and the 1944-45 'Dutch famine' on recalled menarcheal age in participants of the DOM breast cancer screening project

Age at natural menopause in a population-based screening cohort: the role of menarche, fecundity, and lifestyle factors

OBJECTIVE

To verify whether a population-based hypothesis (age at menarche and age at natural menopause have an inverse relationship) also applies at the level of the individual and to investigate what other factors predict age at natural menopause.

DESIGN

Prospective cohort study (the Doorlopend Onderzoek Morbiditeit/Mortaliteit [DOM] project).

SETTING

Prevention Breast Cancer Screening Centre, Utrecht, The Netherlands.

PATIENT(S)

A cohort of 3,756 Dutch women, born between 1911 and 1925, participating in a population-based breast cancer screening program, who experienced a natural menopause. Three samples of women were studied: a sample who did not use oral contraceptives (OCs) (n = 3,347), a sample of OC users (n = 409), and a combined sample of OC users and nonusers (n = 3,756).

MAIN OUTCOME MEASURE(S)

Age at menopause and menarche, fertility patterns, OC use, height, weight, smoking, and demographic variables.

RESULT(S)

No relation was found between age at menarche and age at natural menopause. The total percentage of variance in age at natural menopause explained by multiple regression including all factors was minimal, ranging from 1.3% to 9.7% in OC users. Linear regression analysis indicated a slight secular trend in age at menopause.

CONCLUSION(S)

Frisch's hypothesis could not be corroborated at the individual level. These results suggest that age at menarche and menopause should be treated as independent risk factors for breast cancer. Modification of age at menopause by lifestyle factors (except possibly for OC use) appears minimal.

Statistical modelling of breast cancer incidence and mortality rates in Scotland

The interpretation of time trends in disease rates can be facilitated using estimable contrasts from age-period-cohort models. Cohort and period trends in breast cancer incidence and mortality rates in Scotland were investigated using contrasts that measure the changes in the linear trends. These contrasts were compared with estimates obtained from mortality rates in the USA and Japan. A significant moderation of both breast cancer incidence and mortality rates was observed in Scotland, associated with cohorts of women born after the Second World War compared with women born between the two world wars. The moderation of breast cancer mortality among cohorts born after 1925 compared with cohorts born before 1925 that was observed in the USA and Japan was also observed in this study. This moderation is not present in the incidence rates. The relative decline in the risk of breast cancer seen in younger cohorts seems to be contradictory to the temporal pattern present among breast cancer risk factors. It may well be that the alteration of eating patterns as a result of rationing in the wartime and immediate post-war period, and the subsequent influence on certain breast cancer risk factors probably produced by such changes, may have had some influence on the development of healthier girls and women. Such speculation could be addressed in a well-designed epidemiological study. There have been no changes in the mortality rate trends with period in Scotland, although the changes in the incidence rate trends with period are consistent with an increase in registration coverage.

Age at menarche and breast cancer risk in nulliparous women

Early age at menarche is a known risk factor for breast cancer, some inconsistency in the literature not withstanding. Relative risks for an early menarcheal onset as compared to a late onset vary from 1.0 to 1.9. To avoid (residual) confounding by parity-related factors a case-control study was conducted among nulliparous women. 135 cases and 540 controls were selected from two population-based screening projects for breast cancer in The Netherlands. Four controls were matched to each case for year of birth, for screening-centre, and for number of screening examinations. Women with a menarcheal age of 10 or 11 years showed a 2.2 times (95% confidence interval: 1.2-4.0) higher risk for breast cancer compared to women who had their first menstrual period at 12 years of age or older.

Body measurements, estrogen availability and the risk of human breast cancer: a case-control study

Recent studies on lifestyle-related mechanisms involved in cardiovascular risk offer important clues for a better understanding of breast-cancer epidemiology. Central body-fat distribution promoted by an affluent dietary intake and a sedentary lifestyle over many years is related to elevated serum triglycerides and free fatty acids, with lower levels of sex-hormone-binding globulin (SHBG). The resulting greater availability of estradiol not bound to SHBG could help to explain the high breast-cancer incidence in Western industrialized countries. We conducted a case-control study comparing 225 women aged 38 to 75 years with operable (stage I or II) breast cancer and 441 women of the same age having no breast cancer who participated in a population-based breast-cancer screening program. Body fatness, as measured by body mass index (BMI), fat distribution as measured by waist-to-hip girth ratio (WHR), body height, serum lipids, SHBG and the available fraction of estradiol were analyzed in a conditional logistic regression, together with family history for breast cancer, reproductive history and smoking. Post-menopausal cases showed no difference in body fatness (BMI), but a significant preponderance of central adiposity (WHR). In contrast, pre-menopausal cases were significantly leaner, but had a similar body-fat distribution as compared with controls. In all women, WHR, and less strongly BMI, was positively correlated with serum levels of triglycerides and available estradiol fractions. An independent, positive linear correlation between body height and relative risk (RR) was observed. Moreover, a significant correlation between SHBG and menarcheal age was seen in cases, but not in controls. These data support our hypothesis that lifestyle relates to breast-cancer risk by metabolic-endocrine mechanisms which modulate the availability of individual sex-steroid concentrations in plasma. The findings of height as a risk factor and adult SHBG levels being correlated with menarcheal age suggest that lifestyle factors promoting breast-cancer development already act around puberty. The leanness of pre-menopausal cases awaits further explanation.