Saturday, December 27, 2008

Physical Activity and Breast Cancer - What About Work?

BrooklynDodger(s) comment: Very few chemicals have been associated with increased breast cancer. This is because most non-drug, non-hormonal agents have been found associated with cancer among workers with substantially higher exposure than the general population. However, there are relatively few women in such cohorts, and so little has come from these studies. Another reason may be inferred from this study. The study found that increased physical activity was associated with decreased breast cancer - a frequently observed effect which translates to a blame the victim tone in the standard cancer control literature ("You got cancer because you were lazy.")

Note that modest amounts of physical activity which conferred protection, "The most physically active group (who walked for 1 hour per day and exercised for 1 hour per week)" Compare that with standing and walking 10 hours a day, pounding steel on the assembly line. So women in industrial and construction occupations would be expected to present with a much reduced risk of breast cancer compared to the general population. Studies of industrial cohorts which might observe breast cancer rates close to expected should be considered studies finding an association between the exposure and breast cancer.


Effect of Physical Activity on Breast Cancer Risk: Findings of the Japan Collaborative Cohort Study

Sadao Suzuki1, Masayo Kojima1, Shinkan Tokudome1, Mitsuru Mori5, Fumio Sakauchi5, Yoshihisa Fujino6, Kenji Wakai2, Yingsong Lin7, Shogo Kikuchi7, Koji Tamakoshi3, Hiroshi Yatsuya4, Akiko Tamakoshi7 for the Japan Collaborative Cohort Study Group
"Purpose: This study aimed to examine prospectively the association between physical activity and breast cancer risk in a non-Western population.
Methods: We analyzed data from the Japan Collaborative Cohort Study, which included 30,157 women, ages 40 to 69 years at baseline (1988-1990), who reported no previous history of breast cancer, and provided information on their walking and exercise habits. The subjects were followed prospectively from enrollment until 2001 (median follow-up period, 12.4 years). Breast cancer incidence during this period was confirmed using records held at population-based cancer registries. The Cox proportional hazards model was used to estimate the hazard ratio (HR) for the association of breast cancer incidence with physical activity.
Results: During the 340,055 person-years of follow-up, we identified 207 incident cases of breast cancer. The most physically active group (who walked for 1 hour per day and exercised for 1 hour per week) had a lower risk of breast cancer (HR, 0.45; 95% confidence interval, 0.25-0.78) compared with the least active group after adjusting for potential confounding factors. The inverse association of exercise on breast cancer was stronger among those who walked for 1 hour per day than those who walked for <1 p =" 0.042).">
Conclusions: Our analysis provided evidence that physical activity decreased the risk of breast cancer. Walking for 1 hour per day and undertaking additional weekly exercise both seemed to be protective against breast cancer, regardless of menopausal status or BMI. (Cancer Epidemiol Biomarkers Prev 2008;17(12):3396–401)

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