Research table: Exercise (physical activity) and breast cancer risk

This summary table contains detailed information about research studies. Summary tables are a useful way to look at the science behind many breast cancer guidelines and recommendations. However, to get the most out of the tables, it’s important to understand some key concepts. Learn how to read a research table.

Introduction: Women who get regular exercise (physical activity) have a lower risk of breast cancer than women who don’t exercise regularly or are inactive. 

Overall, studies show regular exercise is linked to a 10%-20% decreased risk of breast cancer (see table below). This benefit is seen most clearly in postmenopausal women, but study findings also show a benefit in premenopausal women.

Learn more about exercise and breast cancer risk. 

Learn about exercise and breast cancer survival.

Learn about the strengths and weaknesses of different types of studies.

See how this risk factor compares with other risk factors for breast cancer. 

Study selection criteria: Prospective cohort studies with at least 800 breast cancer cases, pooled analyses and meta-analyses.

Table notes: Relative risk above 1 indicates increased risk. Relative risk below 1 indicates decreased risk. 

MET (metabolic equivalent) hours are often used as a measure of physical activity. One MET hour equals the energy used to sit quietly for one hour. 

Different activities have different MET scores. Moderate activities, like mowing the lawn or slow dancing, range from 3-6 MET hours. Vigorous activities, like playing tennis or jogging, score higher than 6 MET hours. For example, walking is 3 MET hours and swimming is 7 MET hours.

Study	Study Population (number of participants)	Follow-up (years)	Levels of Activity Compared	Relative Risk of Breast Cancer in Physically Active Women Compared to Inactive Women, RR (95% CI)
				Before menopause	After menopause	Before and after menopause combined
Prospective cohort studies
EPIC [1]	257,805 (8,034 cases)	12	More than 42 vs. 14 or fewer MET hr/wk recreational activity	0.88 (0.72-1.07)	0.97 (0.91-1.05)	0.96 (0.90-1.03)
NIH-AARP Diet and Health Study [2]	106,126 (7,088 cases)	13	At least 4 hr/wk vs. inactive		0.91 (0.84-0.98)
Nurses’ Health Study [3]	95,396 (4,782 cases)	20	27 or more vs. less than 3 MET hr/wk		0.88 (0.79-0.98)
Cancer Prevention Study II-Nutrition Cohort [4]	73,615 (4,760 cases)	13	More than 42 vs. 7 or fewer MET hr/wk		0.75 (0.63-0.89)
			7 or more vs. 3 or fewer hr/wk walking		0.86 (0.75-0.98)
French E3N cohort [5-6]	90,509 (3,424 cases)	11	22-34 MET hr/wk recreational activity vs. inactive			0.88 (0.79-0.98)
			34 or more MET hr/wk recreational activity vs. inactive			0.81 (0.72-0.92)
UK Biobank [7]	184,608 (3,189 cases)	6	High vs. low level of activity	0.77 (0.62-0.96)	0.83 (0.74-0.93)
California Teachers Study [8]	110,599 (2,649 cases)	7	58 or more MET hr/wk physical activity vs. low level of physical activity			1.03 (0.88-1.19)†
Women’s Health Initiative [9]	155,723 (2,610 cases)	8	17 or more hr/wk vs. no activity		0.85 (0.74-0.98)
Iowa Women’s Health Study [10]	36,363 (2,548 cases)	15	High vs. low level of activity		0.91 (0.82-1.01)
National Breast Cancer Screening Study-Canada [11]	40,318 (2,545 cases)	16	At least 1 hr/day vigorous physical activity vs. inactive	0.87 (0.68-1.09)	1.00 (0.78-1.29)	0.93 (0.78-1.10)
Norwegian-Swedish Women’s Lifestyle and Health Cohort Study [12]	99,504 (1,166 cases)	9	Vigorous activity vs. no activity	1.24 (0.85-1.82)
Breast Cancer Detection Demonstration Project Follow-up Study [13]	32,269 (1,506 cases)	8	High vs. low level of activity		0.87 (0.74-1.02)
Netherlands Cohort Study [14]	62,537 (1,208 cases)	7	More than 90 minutes/day of activity vs. less than 30 minutes/day		0.76 (0.58-0.99)
Rainey et al. [15]	57,654 (957 cases)	4-6	1½-2½ vs. less than 1½ hr/day recreational activity			1.07 (0.90-1.27)
			2½ or more vs. less than 1½ hr/day recreational activity			1.11 (0.94-1.31)
U.S. Radiologic Technologies cohort [16]	45,631 (864 cases)	9	At least 97 vs. less than 10 MET hr/wk			0.91 (0.74-1.13)
			Walking/hiking at least 10 hr/wk vs. never walking/hiking			0.57 (0.34-0.95)
Nurses’ Health Study II [17-18]	110,468 (849 cases)	10	27 or more vs. less than 3 MET hr/wk	1.04 (0.82-1.33)
Pooled and meta-analyses
Nielson et al. [19]	58 studies		High vs. low level of moderate to vigorous activity		0.79 (0.74-0.84)‡
	43 studies		High vs. low level of moderate to vigorous activity	0.80 (0.74-0.87)‡
Pizot et al. [20]	38 studies (116,304 cases)		High vs. low level of activity	0.87 (0.78-0.96)	0.88 (0.85-0.91)	0.88 (0.85-0.90)
Kyu et al. [21]	35 studies		10-67 vs. less than 10 MET hr/wk			0.97 (0.94-1.00)
Hardefeldt et al. [22]	35 studies		High vs. low level of low to moderate activity			0.73 (0.65-0.81)
			High vs. low level of vigorous activity			0.79 (0.72-0.86)
World Cancer Research Fund International – Continuous Update Project [23]	21 studies		High vs. low level of recreational activity		0.88 (0.82-0.94)
	12 studies		High vs. low level of recreational activity	0.89 (0.75-1.04)
Timmins et al. [24]	19 studies (10,231 cases)		High vs. low level of recreational activity	0.90 (0.85-0.95)
Physical Activity Collaboration of the National Cancer Institute’s Cohort Consortium [25]	10 studies		High vs. low level of activity			0.93 (0.90-0.96)
Matthews et al. [26]	8 studies (17,983 cases)		1-7 MET hr/wk vs. low level of activity			0.94 (0.91-0.97)
			8 to less than 15 MET hr/wk vs. low level of activity			0.90 (0.86-0.94)
			15 to less than 30 MET hr/wk vs. low level of activity			0.88 (0.84-0.91)
			30 or more MET hr/wk vs. low level of activity			0.86 (0.82-0.90)
African American Breast Cancer Epidemiology and Risk (AMBER) Consortium [27]	4 studies (3,856 cases)		High vs. low level of vigorous activity			0.88 (0.81-0.96)

† Findings also showed a decreased risk of estrogen receptor-negative breast cancers among women with the highest levels of physical activity (more than 5 hours per week vs. inactive, relative risk was 0.53 (0.33-0.85)). There was no link between physical activity and the risk of estrogen receptor-positive breast cancers.

‡ Findings for cohort studies only were similar. The relative risk for 13 cohort studies of premenopausal breast cancer risk was 0.83 (0.72-0.96). The relative risk for 26 cohort studies of postmenopausal breast cancer risk was 0.90 (0.85-0.95). 

References

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Updated 06/06/24