Physical Activity and Risk of Breast Cancer: A Meta-Analysis of 38 Cohort Studies in 45 Study Reports

Abstract

To evaluate and quantify the association between physical activity (PA) and risk of breast cancer. Methods: A systematic review meta-analysis was conducted. The literature was independently and manually searched by 2 reviewers through 3 English databases (PubMed, Embase, and ISI Web of Science) for data till October 2017. The quality of included studies was assessed by the Newcastle-Ottawa Quality Assessment Scale. Fixed-effects models were used to estimate the pooled relative risk and 95% confidence intervals (95% CI). Doseeresponse analysis was chosen for quantifying the association between PA and risk of breast cancer. The Begg test and the Egger test were used to estimate potential publication bias. Heterogeneity between studies was evaluated with I 2 statistics. Results: The meta-analysis included 38 cohort studies published between 1994 and 2017, which included 68 416 breast cancer cases. The overall relative risk (ORR) for breast cancer was 0.87 (95% CI 0.84-0.90). The inverse association was consistent among all subgroup analyses. In subgroup analysis by menopausal status, the ORR of breast cancer was 0.83 (95% CI 0.79-0.87) for premenopausal status and 0.91 (95% CI 0.85-0.97) for postmenopausal status. In subgroup analysis by PA type, the ORR for total activity was 0.87 (95% CI 0.81-0.93), for recreational activity 0.88 (95% CI 0.85-0.91), for occupational activity 0.91 (95% CI 0.84-0.99), and for nonoccupational activity 0.87 (95% CI 0.83-0.92). The risk of breast cancer was significantly lower in people with exposure periods longer than 1 year and less than 5 years (ORR 0.62; 95% CI 0.46-0.78), followed by those with lifetime activity (ORR 0.81; 95% CI 0.69-0.93). The ORR for subjects with body mass index of less than 25 kg/m 2 (0.88; 95% CI 0.83-0.93) was close to that for subjects with body mass index of more than 25 kg/m 2 (0.87; 95% CI 0.77-0.97). A linear relationship was found between breast cancer risk and PA (recreational activity and total activity), and the ORR was reduced by 3% (95% CI 0.95-0.99) for every 10 metabolic equivalent of energy hours per week increment in recreational PA and by 2% (95% CI 0.97-0.99) for every 10 metabolic equivalent of energy hours per week increment in total PA. Conclusions: PA is significantly associated with a decrease in the risk of breast cancer.

The Burden and Trends of Breast Cancer From 1990 to 2017 at the Global, Regional, and National Levels: Results From the Global Burden of Disease Study 2017

“…Four components were used to estimate the attributable burden of causes to risk factors, including the estimate of the burden metric being assessed (i.e., number of deaths, YLLs, YLDs, or DALYs), the levels of exposure for the risk factor, the counterfactual level of risk factor exposure, and the relative risk of the outcome caused by the exposure. The GBD comparative risk assessment summarized and updated 476 riskoutcome pairs supported by convincing or probable evidence in 2017, and we identified all five risk factors listed as paired outcomes of breast cancer, including alcohol use, high body mass index (BMI), high fasting plasma glucose, low physical activity, and tobacco smoking (19)(20)(21)(22)(23)(24)(25).…”

Rowing Training in Breast Cancer Survivors: A Longitudinal Study of Physical Fitness

“…Physical activity decreases the duration and intensity of fatigue [ 8 , 9 ], reduces anxiety and depression [ 10 ], increases muscle mass and strength, decreases disability in the upper extremities [ 11 ] and improves quality of life [ 12 , 13 ], as well as restoring and even improving functionality and well-being in women who have overcome breast cancer [ 14 ]. Several meta-analyses and reviews affirm that physical activity also contributes to reducing the risk of breast cancer recurrence [ 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 ], while others have obtained neutral results, implying that physical activity does not cause any changes [ 29 , 30 , 31 ].…”

The Association between Lifestyle Factors and the Risk of Developing Breast Cancer in Jordanian Women

“…For the physical activity (PA), Ma et al showed that substantially increasing the amount of total recreational PA in adulthood decreases the risk of BC 10) . A recent meta-analysis pointed out that PA was significantly associated with reduced the risk of BC in their meta-analysis and they advised that PA should be advocated for the primary prevention of BC 11) . Their evidence showed that a linear relationship was found between breast cancer risk and PA (recreational activity and total activity), and the risk was reduced by 3% for every 10 metabolic equivalent of energy hours per week increment in recreational and total PA 11) .…”

“…A recent meta-analysis pointed out that PA was significantly associated with reduced the risk of BC in their meta-analysis and they advised that PA should be advocated for the primary prevention of BC 11) . Their evidence showed that a linear relationship was found between breast cancer risk and PA (recreational activity and total activity), and the risk was reduced by 3% for every 10 metabolic equivalent of energy hours per week increment in recreational and total PA 11) . Therefore, the objectives of this study were to evaluate the association between the levels of PA, mass index (BMI); and some lifestyle factors and the risk of BC among Jordanian women.…”