The new findings fit with research showing that regular physical activity is linked to a lower risk of developing other cancers, including breast, colon, and kidney cancer.

However, the link with prostate cancer is less clear-cut, the authors of the new paper write.

To better understand this connection, they examined data on 57,652 men from a Swedish occupational health profile assessment database for the period 1982 to 2019.

This included information on men’s physical activity; lifestyle; perceived health; and height and weight measurements, which were used to calculate body mass index (BMI).

All men also had at least two cardiorespiratory fitness tests, which involved riding a stationary cycle. This test measures the amount of oxygen used while a person exercises at maximum effort.

During an average follow-up period of 7 years, an increase in absolute cardiorespiratory fitness was linked to a 2% lower risk of developing prostate cancer.

This was after researchers took into account other factors that could potentially affect the risk of prostate cancer, including age, education level, year the test was taken, BMI, and smoking status.

However, no link was found between a change in cardiorespiratory fitness and the risk of dying from prostate cancer.

Researchers next divided men into three groups based on whether they increased their cardiorespiratory fitness by 3% or more; decreased their fitness by 3% or more; or remained about the same. This is a relative change in fitness.

Men whose fitness improved 3% or more a year on average were 35% less likely to develop prostate cancer when researchers took into account all the other factors.

How much exercise is needed to get this kind of cardio boost? Research shows that a person can improve their cardiorespiratory fitness by up to 16% by doing certain exercise programs for one year or less.

What puts you at risk for prostate cancer

When researchers grouped men based on cardiorespiratory fitness during their first cycle test, the results were only statistically significant for the group that started with a moderate level of fitness.

This shows there was a clear link between improved fitness and lower prostate cancer risk for this group — in this case, a 15% lower risk on average.

However, it doesn’t mean that more fit or less fit men won’t benefit from a cardio boost, just that the data from the study couldn’t say either way.

The results of the study should be viewed with some caution. First, it is an observational study, so it can’t show cause-and-effect.

Other factors — in particular, genetics — play a major role in determining a person’s risk of developing prostate cancer, as well as their cardiorespiratory fitness, the researchers write.

Dr. Will Jin, an assistant professor of clinical radiation oncology at the Sylvester Comprehensive Cancer Center at the University of Miami Miller School of Medicine, also pointed out that men who started with higher cardiorespiratory fitness had a lower body mass index (BMI), were more likely to have never smoked, exercised more often during the week, and were younger than the other groups.

These differences from the other groups could affect their prostate cancer risk, as well as their cardiorespiratory fitness.

In addition, the average age of participants in the study was 41 years old. In comparison, the average age when men are first diagnosed with prostate cancer is 67 years old according to the American Cancer Society.

“Knowing that this is a low-risk cohort for prostate cancer, we must have different expectations for how this study can be applied to an average man,” said Jin.

Urologist and urologic oncologist Dr. Ramkishen Narayanan, from the Center for Urologic Health at the Disney Family Cancer Center in Burbank, CA, also not involved in the research, did, however, appreciate that the study focused on diagnosis of prostate cancer, and not mortality, since the number of men who die is so low that meaningful analysis is difficult.

“You’re talking about 1% at a mean followup of seven years. So that followup is not terribly long and the numbers are small,” he said.

While the study has limitations, it provides additional support for the benefits of cardiorespiratory fitness — which in addition to a lower risk of certain cancers, includes a lower risk of heart attack and stroke.

Still, more research is needed to understand why men who improved their fitness had a lower risk of prostate cancer.

“What does a change in [cardiorespiratory fitness] actually represent that could impact cancer risk?” said Jin, pointing out that fitness variables are sometimes a proxy for other, more direct factors.

“We need to identify something measurable that can lead to reduced prostate cancer risk,” he said, “and then we need to know what the intervention is.”

For example, did men who improved their cardiorespiratory fitness have access to healthier food and a community that encouraged healthy behaviours? Or were other factors involved that lowered the risk of prostate cancer and improved men’s cardiorespiratory fitness at the same time?

”While this study had an impressive population size and strong credibility, I’m left with more questions than answers,” said Jin. “But that’s not a bad thing.”

The research group he is involved with at the University of Miami Miller School of Medicine is trying to identify dietary behaviours or measures related to body composition that might predict who has a higher risk of developing prostate cancer and how well they do with treatment.

“For patients, there aren’t many things that they can do to affect their prostate cancer outcomes,” he said. “So, identifying a risk factor that’s modifiable would be a game changer.”

Cardiologist Dr. Jayne Morgan noted a lack of information regarding “whether men with higher fitness levels or higher cardiorespiratory fitness also have different health habits with regard to types of food consumed, amounts of sleep obtained, hobbies, level of engagement with the medical establishment, obesity, employment — these men were all employed — and other lifestyle choices that can impact health and even cancer risk.”

Takeaway

Dr. Morgan listed the items she would like to see addressed in a subsequent, more robust study. These are:

1. utilize a VO2 max measurement that is validated.
2. control for co-morbidities and lifestyle factors.
3. perform randomized control trials.
4. include other populations, especially Black men
5. increase the number of timepoints
6. adjust and randomize for age.

Research has shown that physical activity is linked to a lower risk of certain cancers, such as breast, colon, and kidney cancer. However, the link with prostate cancer is less clear.

To understand this connection, researchers examined data on over 57,000 men and found that those who improved their cardiorespiratory fitness saw decreases in their prostate cancer risk. No similar link was seen for the risk of dying from prostate cancer.

The study is observational, so can’t show cause and effect. Other factors, especially genetics, play a role in determining a man’s risk of prostate cancer and cardiorespiratory fitness.