A prospective study of occupational physical activity and breast cancer risk

Abstract

Purpose Physical activity has been associated with reduced breast cancer risk, but studies of occupational activity have produced inconsistent results. The purpose of this study was to evaluate the relationship between occupational physical activity and breast cancer in a prospective study of women with a family history of breast cancer. Methods We studied breast cancer risk in 47,649 Sister Study participants with an occupational history. Information on occupational activity and breast cancer risk factors was collected during baseline interviews (2004-2009). Physical activity at each job was self-reported and categorized as mostly sitting, sitting and standing equally, mostly standing, and active. Multivariable Cox proportional hazards regression was used to evaluate associations between lifetime occupational activity and incident breast cancer, after adjusting for established risk factors and recreational activity. Results During follow-up, a total of 1,798 breast cancer diagnoses were reported. Compared with women who did not spend any time in active jobs, women who spent a high proportion (≥75%) of their working years in active jobs had a reduced risk of breast cancer (HR = 0.72; 95% CI = 0.52-0.98). Associations were strongest among overweight (HR = 0.64; 95% CI = 0.42-0.98) and postmenopausal (HR = 0.67; 95% CI = 0.45-0.98) women. Conclusions Occupational activity was associated with a reduced risk of breast cancer. Occupational activity is a domain of physical activity that should be further examined in studies of postmenopausal breast cancer risk. Additional research is necessary to better understand the mechanisms between occupational activity, body size, and breast cancer.

Risk of cancer and longest‐held occupations in Japanese workers: A multicenter hospital‐based case‐control study

“…The present study is in agreement with previous studies reporting an association between high physical activity (including both occupational and leisure time) and cancer occurrence . Although the mechanism is as yet undefined, both hormonal and nonhormonal causal relationships between physical activity and cancer are suspected .…”

“…Previous studies have investigated the association between occupation and cancer mortality . But, whether occupational physical activity is associated with a risk of cancer is unclear . In Japan, many working people spend a large proportion of their life in gainful employment.…”

The association between metabolic health, obesity phenotype and the risk of breast cancer

“…Response rates were >92% for all follow-ups. 31 Self-reported incident breast cancers and tumor characteristics were verified by medical records, which had been obtained for 82% of the 1,388 cases at time of this data release. Agreement was high between self-reported breast cancer diagnosis and medical records (99.4%).…”

Sedentary work and the risk of breast cancer in premenopausal and postmenopausal women: a pooled analysis of two case–control studies

“…A 2014 meta-analysis that examined the association between occupational sitting time and breast cancer reported a summary risk estimate of 1.03 for the highest versus lowest levels of sedentary work, and three subsequent studies (two cohort and one case–control) have also found no association between sitting time at work, total sitting time and/or time spent sitting watching television and the risk of breast cancer 12 30 31. An updated meta-analysis published in 2015 found that occupational sedentary behaviour was associated with a 10% increased risk of breast cancer 10.…”