OBJECTIVE: To clarify whether type and timing of physical activity affect postmenopausal breast cancer risk. METHODS: In a population-based case-control study within the Swedish female population 50-74 years of age, 3347 women with invasive, postmenopausal breast cancer (84% of all eligible) and 3455 controls (82% of all selected) reported on past leisure-time physical activity. Record linkage to decennial census data (1960-1990) provided estimates of their occupational physical activity. Odds ratios with 95% confidence intervals were estimated by multivariate logistic regression. RESULTS: After adjustment for potential confounders, women in sedentary occupations during their reproductive years (25-44 years of age) had a 50% higher risk for postmenopausal breast cancer, compared to those with the physically most demanding jobs. Only the most recent leisure-time physical activity was associated with a significant risk reduction. Women with the combination of sedentary jobs and lack of leisure-time exercise had a three-fold higher risk of breast cancer, compared to the physically most active both inside and outside the workplace. CONCLUSION: Effects of occupational and leisure-time physical activity on breast cancer risk appear to have different latency times, and/or to be effect-modified by age or reproductive status. Although chance might explain our findings, it is advisable to consider type and timing of physical activity in future studies.
OBJECTIVE: To clarify whether type and timing of physical activity affect postmenopausal breast cancer risk. METHODS: In a population-based case-control study within the Swedish female population 50-74 years of age, 3347 women with invasive, postmenopausal breast cancer (84% of all eligible) and 3455 controls (82% of all selected) reported on past leisure-time physical activity. Record linkage to decennial census data (1960-1990) provided estimates of their occupational physical activity. Odds ratios with 95% confidence intervals were estimated by multivariate logistic regression. RESULTS: After adjustment for potential confounders, women in sedentary occupations during their reproductive years (25-44 years of age) had a 50% higher risk for postmenopausal breast cancer, compared to those with the physically most demanding jobs. Only the most recent leisure-time physical activity was associated with a significant risk reduction. Women with the combination of sedentary jobs and lack of leisure-time exercise had a three-fold higher risk of breast cancer, compared to the physically most active both inside and outside the workplace. CONCLUSION: Effects of occupational and leisure-time physical activity on breast cancer risk appear to have different latency times, and/or to be effect-modified by age or reproductive status. Although chance might explain our findings, it is advisable to consider type and timing of physical activity in future studies.
Authors: Lauren E McCullough; Sybil M Eng; Patrick T Bradshaw; Rebecca J Cleveland; Susan L Teitelbaum; Alfred I Neugut; Marilie D Gammon Journal: Cancer Date: 2012-06-25 Impact factor: 6.860
Authors: A Pronk; B-T Ji; X-O Shu; W-H Chow; S Xue; G Yang; H-L Li; N Rothman; Y-T Gao; W Zheng; C E Matthews Journal: Br J Cancer Date: 2011-09-20 Impact factor: 7.640
Authors: Kristjana Einarsdóttir; Keith Humphreys; Carine Bonnard; Juni Palmgren; Mark M Iles; Arvid Sjölander; Yuqing Li; Kee Seng Chia; Edison T Liu; Per Hall; Jianjun Liu; Sara Wedrén Journal: PLoS Med Date: 2006-05-09 Impact factor: 11.069
Authors: Kristjana Einarsdóttir; Tove Rylander-Rudqvist; Keith Humphreys; Susanne Ahlberg; Gudrun Jonasdottir; Elisabete Weiderpass; Kee Seng Chia; Magnus Ingelman-Sundberg; Ingemar Persson; Jianjun Liu; Per Hall; Sara Wedrén Journal: Breast Cancer Res Date: 2005-09-14 Impact factor: 6.466