Risk Factors for Breast Cancer - How to Keep them Straight?

Given the lack of cohorts of women with heavy occupational chemical exposures, environmental chemical causes of cancer among women are poorly identified. The majority of human carcinogens have first been observed in occupational settings. Which is not a deal for lung cancer, we expect the agents to be the same. But for female breast cancer we need data in females.

[Actually, the overwhelming risk factor for breast cancer is being female. Estrogen poisoning?]

The next issue is, what are the population risk factors for breast cancer, so as to look at modifiers of a chemical exposure effect in an occupational population? What is the appropriate healthy worker effect among women for female breast, ovarian and other cancers?

The most objective issue is physical activity. Physical activity is generally agreed to be protective, although the biological basis for this is speculative. Factory workers have way more physical demands than the general population, and this is likely more pronounced for woman than men. So factory women would be expected to have reduced breast cancer compared to the general population. This has been observed.

What about other risk factors? Early menarche [and late or no child birth] is a risk factor for breast cancer. Height is a risk factor for breast cancer. However, early menarche is a risk factor for not being tall. In this paper, as a population, in Europe, women as a population are getting taller in spite of having earlier menarche. Both height and menarche are plausibly products of improved nutrition.

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American Journal of Epidemiology 2005 162(7):623-632; doi:10.1093/aje/kwi260


Age at Menarche in Relation to Adult Height
The EPIC Study
N. C. Onland-Moret1, P. H. M. Peeters1, C. H. van Gils1, F. Clavel-Chapelon2, T. Key3, A. Tjønneland4, A. Trichopoulou5, R. Kaaks6, J. Manjer7, S. Panico8, D. Palli9, B. Tehard2, M. Stoikidou5, H. B. Bueno-De-Mesquita10, H. Boeing11, K. Overvad12, P. Lenner13, J. R. Quirós14, M. D. Chirlaque15, A. B. Miller16, K. T. Khaw17 and E. Riboli6
1 Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht, the Netherlands2 E3N-EPIC Group, Institute Gustav Roussy, National Institute for Health and Medical Research (INSERM), Villejuif, France3 Cancer Research UK Epidemiology Unit, University of Oxford, Oxford, United Kingdom4 Institute of Cancer Epidemiology, Danish Cancer Society, Copenhagen, Denmark5 Department of Hygiene and Epidemiology, Medical School, University of Athens, Athens, Greece6 International Agency for Research on Cancer (IARC), Lyon, France7 Department of Community Medicine, Malmö University Hospital, Malmö, Sweden8 Dipartimento di Medicina Clinica e Sperimentale, Universita Federico II, Naples, Italy9 Molecular and Nutritional Epidemiology Unit, Centro per lo Studio e la Prevenzione Oncologica, Istituto Scientifico della Regione Toscana, Florence, Italy10 Centre for Nutrition and Health, National Institute for Public Health and Environment, Bilthoven, the Netherlands11 Department of Epidemiology, German Institute of Human Nutrition, Bergholz-Rehbruecke, Germany12 Department of Clinical Epidemiology, Aalborg Hospital, Aarhus University Hospital, Aalborg, Denmark13 Department of Oncology, Umeå University, Umeå, Sweden14 Public Health and Health Planning Directorate, Asturias, Spain15 Epidemiology Department, Regional Health Council, Murcia, Spain16 Division of Clinical Epidemiology, Deutsches Krebsforschungszentrum, Heidelberg, Germany17 Clinical Gerontology Unit, University of Cambridge, Cambridge, United Kingdom
Correspondence to N. C. Onland-Moret, Julius Center for General Practice and Patient Oriented Research, Room Str-6.119, University Medical Center Utrecht, P.O. Box 85500, 3508 GA Utrecht, the Netherlands (e-mail: N.C.Onland@jc.azu.nl (image placeholder).
In the last two centuries, age at menarche has decreased in several European populations, whereas adult height has increased. It is unclear whether these trends have ceased in recent years or how age at menarche and height are related in individuals. In this study, the authors first investigated trends in age at menarche and adult height among 286,205 women from nine European countries by computing the mean age at menarche and height in 5-year birth cohorts, adjusted for differences in socioeconomic status. Second, the relation between age at menarche and height was estimated by linear regression models, adjusted for age at enrollment between 1992 and 1998 and socioeconomic status. Mean age at menarche decreased by 44 days per 5-year birth cohort (ß = –0.12, standard error = 0.002), varying from 18 days in the United Kingdom to 58 days in Spain and Germany. Women grew 0.29 cm taller per 5-year birth cohort (standard error = 0.007), varying from 0.42 cm in Italy to 0.98 cm in Denmark. Furthermore, women grew approximately 0.31 cm taller when menarche occurred 1 year later (range by country: 0.13–0.50 cm). Based on time trends, more recent birth cohorts have their menarche earlier and grow taller. However, women with earlier menarche reach a shorter adult height compared with women who have menarche at a later age.