PHYSICAL ACTIVITY AND THE PRIMARY PREVENTION OF CANCER
Section snippets
METHODOLOGIC PROBLEMS
“Physical activity,” “physical fitness,” and “exercise” are terms used often together, but need to be distinguished. Physical activity is a behavior consisting of any bodily movement produced by skeletal muscles resulting in energy expenditure. Epidemiologists often divide daily “physical activity” into the energy used during work activities and the energy used during leisure (or recreational) activities. “Physical fitness” is a set of attributes that determine the ability of a person to
Epidemiology
Several studies that have evaluated the relationship between physical activity or physical fitness and cancer are summarized in Table 1. Physical activity was estimated by a variety of methods. The subjects in all the studies were predominantly white.
Two early studies of men used participation in college athletics as an indicator of physical activity or fitness.68, 74 Neither of these studies found a relationship between college sports participation and cancer mortality; however, participation
Epidemiology
Colon cancer has been the most extensively studied, site-specific cancer with regard to the impact of physical activity on the risk of development. Tables 3, 4,
Study Physical ActivityAssessment Design Controlled Variables Results Slattery et al87 Self-report total Case control Age, BMI, fiber consumption OR 0.5*, High:Low activity Wu et al104 Leisure-time 4.5 Age RR 0.89 (NS), Most:Least active Slattery et al90 Total Case-control Age, BMI, diet OR 0.48*,
Epidemiology
An association of decreased breast cancer risk with regular physical activity was first suggested by Frisch et al in 198523 when they reported a significantly greater prevalence of breast cancer in women who were not involved with athletics in college compared with athletes 1 to 56 years after graduation. Since that time, several studies have investigated the relationship between breast cancer and physical activity (Table 7). Of the 13 studies summarized in Table 7, 8 showed a significant
Epidemiology
Eleven studies that evaluated the effect of physical activity levels and prostate cancer are summarized in Table 8. Of the studies that measured occupational physical activity, three found a significant decreased risk of prostate cancer with increased activity,10, 58, 97 one reported a nonsignificant trend toward decreased risk,1 and one study did not find a relationship between physical activity and prostate cancer risk.77 All of the studies that assessed leisure-time physical activity found
CONCLUSION
There is a growing body of epidemiological evidence that physical activity may decrease the risk cancer mortality. The evidence for a protective effect of regular physical activity against colon cancer is particularly strong. Data are accumulating that suggest an inverse relationship between physical activity and breast and prostate cancer. Several mechanisms by which exercise may decrease cancer development have been proposed, including immunologic enhancement, increased antioxidant defense,
ACKNOWLEDGMENT
The author would like to thank Tanya Emch for her help in the preparation of this manuscript.
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Non-exercise estimated cardiorespiratory fitness and cancer incidence: The NIH-AARP diet and health study
2023, Journal of Sport and Health ScienceCardiorespiratory fitness and cancer in women: A prospective pilot study
2019, Journal of Sport and Health ScienceCitation Excerpt :Cancer is a broad and varied group of diseases; therefore, the biological pathways by which CRF influences cancer are likely to differ based on cancer type and site. Potential protective mechanisms might include improved insulin sensitivity, decreased chronic inflammation, enhanced regulation of sex steroid hormones and growth-related hormones, decreased adipose tissue, optimized immune function, elevated antioxidant capacity, enhanced DNA repair, cell proliferation, and apoptosis.42–45 These mechanisms likely interact in a complex manner by blocking cancer cell initiation and countering cancer cell replication among fit women.
Sex-specific effects of leisure-time physical activity on cause-specific mortality in NHANES III
2017, Preventive MedicineCitation Excerpt :LTPA was also associated with other causes of death. In line with this study, the association of physical activity, in particular, but not exclusively LTPA, and cause-specific mortality was observed previously (Alfano et al., 2004; Arem et al., 2014; Borch et al., 2011; Davey Smith et al., 2000; Hu et al., 2005; Ibrahim and Al-Homaidh, 2011; Je et al., 2013; Kiningham, 1998; Lam et al., 2004; Laukkanen et al., 2011; Loprinzi et al., 2012; Nocon et al., 2008; Orsini et al., 2008; Schmid and Leitzmann, 2014; Sluik et al., 2012; Sternfeld, 1992; Wu et al., 2015; Zhong et al., 2014). In the study by Lam et al. (2004), not only a risk reduction for CVD, cancer and respiratory diseases mortality for physically active participants was observed, but it was also estimated that 20% of all 31,349 registered deaths in 1998 in Hong Kong were assignable to physical inactivity in participants aged over 35 years.
Cardiorespiratory fitness and cancer incidence in men
2017, Annals of EpidemiologyCitation Excerpt :Potential protective mechanisms related to higher CRF might include improved insulin sensitivity, reduced chronic inflammation, enhanced regulation of sex steroid hormones, growth-related hormones, decreased adipose tissue, optimized immune function, elevated antioxidant capacity, enhanced DNA repair, cell proliferation, and apoptosis processes [20,44,45]. These mechanisms likely interact in a complex manner by blocking cancer cell initiation and countering cancer cell replication among fit individuals [23,44,46,47]. However, despite growing observational evidence supporting the concept that CRF has a role in cancer prevention [23–25,27], prospective controlled studies addressing the mechanisms associated with exercise intervention on cancer genesis are warranted.
Cardiorespiratory fitness, physical activity and cancer mortality in men
2017, Preventive MedicineCardiorespiratory fitness and lung cancer risk: A prospective population-based cohort study
2016, Journal of Science and Medicine in SportCitation Excerpt :This protective effect of physical activity may be due to the improved immune system function, by increasing natural killer cells.22 Physical training may improve monocytes, macrophages and natural killer cells, these non-specific immune systems have protective effects from malignancies.23 Additional benefits of physical activity in cancer prevention may include appropriate body mass, hormonal levels and healthy energy balance.24
Address reprint requests to Robert Kiningham, MD, Department of Family Medicine, University of Michigan Medical School, 1018 Fuller Street, Ann Arbor, MI 48109-0707
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Department of Family Medicine, University of Michigan Medical School, Ann Arbor, Michigan