A systematic review by New Zealand researchers seeks to clarify the relationship between physical activity and testicular cancer.
Testicular cancer is common in men between the ages of 15 to 40 years, and with a rise in global incidences of testicular cancer, researchers seek to find evidence of risk factors. One of the research areas of interest is how physical activity is associated with testicular cancer, for better or worse.
Researchers in New Zealand recently conducted a systematic review of the literature examining whether physical activity is associated with an increased or decreased risk of testicular cancer. They evaluated—if there is an association—the dose-response (or cause and effect), relationship, and whether there are certain periods over the course of one’s life during which physical activity affects the risk of testicular cancer. Their review included studies up to November 11, 2016, that were available in Ovid Medline, Embase, Scopus, or Web of Science databases. The results were recently published in BMC Cancer. This review included studies that evaluated associations between physical activity and testicular cancer and had a calculable 95% scientific margin of confidence.
The database search yielded 650 papers from multiple countries dated from 1970 to 2006. Of these, 13 relevant studies were chosen for inclusion in the final analysis. The results were not as conclusive as the researchers had hoped for several reasons: the type and intensity of physical activity varied widely from study to study, many studies included self-reported assessments which leave the possibility of personal bias as a confounding obstacle, the cause-effect relationship in four studies showed directly conflicting results. In fact, for every study that demonstrated that physical activity increased the risk of testicular cancer, another study demonstrated the opposite, that increased physical activity reduced the risk of testicular cancer.
The researchers concluded that there is no clear evidence that physical activity is associated with an increased risk of testicular cancer. The research team acknowledges the need for more in-depth studies with a central method or classification of physical activity. The researchers claim that just because there is a current lack of evidence on this topic, it should not be interpreted as a non-existent relationship.
Written by Cooper Powers, BSc
Reference: Huang, S., Signal, V., Sarfati, D., Shaw, C., Stanley, J., McGlynn, K., Gurney, J. (2018). Physical activity and risk of testicular cancer: a systematic review. BMC Cancer, 18(189). DOI https://doi.org/10.1186/s12885-018-4093-3