The link between physical activity and cancer

Physical activity has long been known to increase a person's chances of living healthy well past retirement. The benefits of physical activity are numerous and include everything from a lower risk for overweight and obesity to improved mental health. Physical activity also has been linked to a lower risk for various diseases, including an assortment of cancers.

The National Cancer Institute notes that the evidence linking physical activity to lower cancer risk comes from observational studies. Observational studies are a type of study in which individuals are observed or certain outcomes are measured. In observational studies examining physical activity, participants will report on their levels of physical activity and are then followed for years. During these studies, no attempt, such as treatment, is made to affect the outcome. The NCI notes that observational studies cannot prove a causal relationship, though they still are invaluable to cancer researchers. Such studies also illustrate the important role that physical activity can play in preventing various types of cancer.

· Bladder cancer: A 2014 meta-analysis of studies published in the British Journal of Cancer found that the risk of bladder cancer was 15 percent lower for individuals with the highest level of recreational or occupational physical activity than in those with the lowest level. That information may be especially valuable to individuals over 55, as the American Cancer Society notes about nine out of 10 people with bladder cancer are 55 or older.

· Breast cancer: A meta-analysis published in the European Journal of Cancer in 2016 found that the most physically active women had a 12 to 21 percent lower risk of breast cancer than those who were the least physically active. Similarly, additional studies have linked physical activity after menopause to a lower risk of breast cancer. That's important to know, as the NCI indicates that doctors most often diagnose breast cancer in women between the ages of 55 and 64.

· Esophageal cancer: Cohort studies are used by researchers to investigate the causes of disease and to establish links between risk factors and health outcomes. A 2014 meta-analysis of nine cohort studies and 15 case-control studies, which compare patients who have a disease or outcome of interest to patients who do not have the disease or outcome, found that the individuals who were the most physically active had a 21 percent lower of risk of esophageal adenocarcinoma than those who were the least physically active. Such findings are significant, as the Mayo Clinic reports that adenocarcinoma is the most common form of esophageal cancer in the United States, while the NCI notes the condition is not curable.

· Kidney (renal cell) cancer: A pooled analysis of more than one million individuals published in JAMA Internal Medicine in 2016 found that leisure-time physical activity was linked to a 23 percent reduced risk of kidney cancer. Leisure-time physical activities can include anything from jogging to dancing to gardening.

Physical activity benefits the body in myriad ways and has been linked to significantly lower risks for various cancers.