Large Study Finds that Exercise Reduces Risk of Developing 26 Cancers

By John Henry Dreyfuss, MDalert.com staff.

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  • Exercise of moderate to vigorous intensity significantly reduced the risk of developing 13 cancers.
  • Rates of reduction ranged from 10% to 26% for the variety of cancers.
  • Study included 1.44 million participants.

Moderate to vigorous physical exercise has been found to reduce the risk of developing 26 types of deadly cancers. The results of a study of 1.44 million participants were published recently in JAMA Internal Medicine.

“Leisure-time physical activity was associated with lower risks of many cancer types. Health care professionals counseling inactive adults should emphasize that most of these associations were evident regardless of body size or smoking history, supporting broad generalizability of findings,” the authors concluded. Lung cancer is one of the most prevalent killers of Americans. Its incidence was reduced by 26% by exercise (Figures 1 and 2).

 

Figure 1. Lung cancer cell division: Image produced by the Centers for Disease Control and Prevention, a subdivision of the United States Department of Health and Human Services.
(Source: Wikipedia/CDC/NIH.)
Data on the participants was gathered through the National Cancer Institute Cohort Consortium. Approximately 1.44 million people self-reported information about the physical activity they did in their leisure time–walking, running, swimming and so on. Their average age was 59, and their average body mass index (BMI) was 26, meaning that many of the participants were overweight. No one had cancer at the time the study began. Over the next 11 years, give or take, about 187,000 incidents of cancer were logged.

Figure 2. Lung cancer incidence in the U.S.
(Source: Wikipedia/CDC/NIH.)

“Leisure-time physical activity is known to reduce risks of heart disease and risk of death from all causes, and our study demonstrates that it is also associated with lower risks of many types of cancer,” said lead author Steven Moore, PhD, MPH, an investigator with the U.S. National Cancer Institute. “Furthermore, our results support that these associations are broadly generalizable to different populations, including people who are overweight or obese, or those with a history of smoking. Health care professionals counseling inactive adults should promote physical activity as a component of a healthy lifestyle and cancer prevention,” he noted.

The Analysis

The authors of this study pooled data from 12 prospective U.S. and European cohorts with self-reported physical activity (baseline 1987-2004). Multivariable Cox regression was used to estimate hazard ratios (HRs) and 95% confidence intervals (CI) for associations of leisure-time physical activity with incidence of 26 types of cancer.

Levels of physical activity were self-reported by the participants and were modeled as cohort-specific percentiles on a continuous basis. Cohort-specific results were synthesized by random-effects meta-analysis. Hazard ratios for high versus low levels of activity were based on a comparison of risk at the 90th vs 10th percentiles of activity. The data analysis was performed during the period January 1, 2014 to June 1, 2015. Leisure-time physical activity of moderate to vigorous intensity reduced the incidence of during the follow-up period. Exercise had the greatest influence on the development of esophageal adenocarcinoma (Figure 3).

Figure 3. Esophageal adenocarcinoma.
(Source: Wikipedia/GNU Free.)
The study included 1.44 million participants (median [range] age, 59 [19-98] years) 57% of whom ere female. Among these participants the researchers found 186,932 cases of cancer during the study period.

Of the 26 types cancers evaluated, moderate to vigorous exercise reduced the risk of developing 13 types. People in the 90th percentile of activity level—versus those in the 10th percentile—had reduced risk of the following cancers:

  • Esophageal adenocarcinoma (42% lower risk)
  • Liver (27% lower risk)
  • Lung (26% lower risk)
  • Kidney (23% lower risk)
  • Gastric cardia (22% lower risk)
  • Endometrial (21% lower risk)
  • Myeloid leukemia (20% lower risk)
  • Myeloma (17% lower risk)
  • Colon (16% lower risk)
  • Head and neck (15% lower risk)
  • Rectal (13% lower risk)
  • Bladder (13% lower risk)
  • Breast (10% lower risk)

Body mass index (BMI) adjustment modestly attenuated associations for several cancers, “but 10 of 13 inverse associations remained statistically significant after this adjustment” the authors explained. The incidence of liver cancer (Figure 4) was reduced by 27%.

Figure 4. Liver cancer that has metastasized from the pancreas.
(Source: Wikipedia/Haymanj.)
Conversely, leisure-time physical activity was associated with higher risks of malignant melanoma (HR 1.27, 95% CI 1.16-1.40) and prostate cancer (HR 1.05, 95% CI 1.03-1.08). Associations were generally similar between overweight/obese and normal-weight individuals. Smoking status modified the association for lung cancer but did not affect the rates developing other types cancer.