Exercise as it relates to Disease/Is physical activity associated with an increased risk of testicular cancer?

Background Research
Testicular cancer (TC) is perhaps one of the more well-known cancers affecting people biologically born men. It is considered an uncommon type of cancer, but is the second most prevalent cancer in young men between 20 and 39. Causes for TC are relatively typical, such as family history, personal health history and infertility. In Australia there were 31 deaths out of 964 cases during 2022, and previously around 10,000 deaths out of 52,000 cases worldwide in 2008. It is estimated that there is a 0.02% chance of dying from TC in 2022, with a 97% chance of surviving at least 5 years post diagnosis.

Physical activity has long been considered an essential part of life and has been proven through numerous studies to reduce certain types of cancers and diseases. However, in regards to TC, research is now beginning to consistently find correlation between higher levels of physical activity and increased TC risk. One study by Anil Srivastava and Nancy Kreiger in 2000 was one the first to find a strong relationship between the two.

This is a conflicting revelation and future studies are paramount within this area to verify the relationship.

Where is the research from?
This research was based on data collected in Ontario, Canada between 1995 and 1996. It’s authors, Anil Srivastava and Nancy Kreiger, are two high level Canadian graduate researchers who released their work in the year 2000.

Their study was conducted at the Johnx Hopkins Bloomberg School of Public Health, currently ranked #1 by U.S. News & World Report.

The research was then presented through the American Journal of Epidemiology (published by Oxford Academic, the largest university press in the world). The American Journal of Epidemiology has been considered a reliable source of information for many decades with consistent impact factor scores ranging between 5.745 (2010) and 4.322 (2017), as well as consistently ranking within the top 6 journal rankings for public, environmental and occupational health until 2011.

What kind of research is this?
The design of this study is that of a Multicentre design. It originally set out to look at multiple different provinces within Canada but only data from 1 was utilised for the final study. It used a medium-sized case-control study methodology.

What did the research involve?
The Data

The data utilised was from the Enhanced Cancer Surveillance Study in the Ontario province in Canada.

- Cases of men diagnosed with TC between January 1, 1995, and December 31, 1996 from the Ontario Cancer Registry were looked at.

- Eligible men between the ages of 20 to 74 were mailed self-administered questionnaires, which resulted in a 76% return rate and totalling 212 cases.

- To create a control group, 904 subjects were randomly selected from the Ontario Ministry of Finance Property Assessment database. This yielded a 64% return from the same mailed-out questionnaire, from which 251 matched control subjects were selected

The Questionnaire

The questionnaire focused on questions regarding frequency and intensity of physical activity during certain life periods; their teens, early 30s and early 50s. Subjects were not asked specifically about the intensity of the exercise they participate in, but rather given examples of activities, such as walking for moderate levels and running for at least 20 minutes for strenuous levels. Questions were also targeted at the subjects’ perceived intensity of physical activity during their occupation, also split by life periods.

Information around BMI, age, height, education, marital status, smoker/non-smoker, vegetable consumption and fruit consumption were also collected.

A concern for the study was the reliance on self-reporting, which could lead to some unreliability. It's well known that people tend to underreport bad habits (smoking in this case) and overreport good habits (amount of exercise, fruit and vegetable consumption). As this was self-administered, there was no possibility for clarification on questions or making sure the numbers reported were accurate. This may lead to the results from the study not accurately reflecting a true relationship.

In the future, it may be more reliable to us an over-the-phone collection method or a face-to-face interview where a discussion can be had to strengthen the reliability of any significant results that might be seen.

Basic Results
The results indicate that high participation levels in strenuous and/or moderate physical activity increased the potential adverse effects regarding risk of TC in multiple populations.

Further broken down it was found that:

• Teens that were active greater than 5 times a week were found to have significant adverse effects in their risk of developing TC (odds ratio (OR) = 2.36, 95 percent confidence interval (CI): 1.20, 4.64)

• Men who worked jobs that involved a moderate or strenuous amount of physical activity within their early 20s displayed a 70-85% increase in their risk of developing TC (strenuous, OR = 1.67, 95 percent CI: 0.92-3.00; moderate, OR = 1.85, 95 percent CI: 1.05-3.26) compared to those men who worked in jobs that involved sedentary behaviour (such as sitting) who had a significantly lower risk

What conclusions can be made from this research?
The research presents a compelling conclusion in that frequent levels (5 or more sessions per week) of moderate-strenuous physical activity during teenage years increases the risk of developing TC later in life. Occupations that include high levels of activity also saw a huge increase of up to 85% in the risk of developing TC during early 20s.

However, something to note is that although that the research presents solid data coming from a reliable source, there are many other research studies concluding the opposite, that there is no association between physical activity and risk of TC,. ]. It is also widely accepted that there is no current effective prevention from developing TC.

This would suggest that seeking to locate and conduct further research is critical in being able to draw confident conclusions regarding the relationship and the risk.

Practical advice
Although this study indicates that physical activity increases adverse effects to the risk of developing TC, it would be unwise to suggest decreasing a man’s physical activity level would be beneficial. This is because physical activity is important in several other factors, such as cardiovascular health, mental health and reducing risks of other cancers and diseases. Although there is a strong correlation seen here, there are many other factors such as family history and infertility which play a much stronger role in the risk of developing TC, not just frequent moderate and strenuous physical activity recreationally or in occupation

However, we cannot disregard the research entirely.

A practical compromise would be developing an age-appropriate screening checklist for risk of developing TC to be used by exercise practitioners which considers all risk factors, including activity levels. If a patient or client indicates high levels of vulnerability, referral to an appropriate medical practitioner would be encouraged for regular screening. This advice not only gives the best possibility for early detection of TC, but also avoids undesirably decreasing physical activity levels and increasing potential health concerns elsewhere.

Further information
Information on causes, symptoms and how to check your testes for signs of TC - https://www.cancer.org.au/cancer-information/types-of-cancer/testicular-cancer

Access to the full research study - https://academic.oup.com/aje/article/151/1/78/89036?login=false