Cardiorespiratory Fitness Linked to 40% Lower Cancer Risk

For men, being physically fit with high cardiorespiratory endurance may reduce the chance of developing nine types of cancer.

Cardiorespiratory fitness, or aerobic fitness, is the ability to perform physical activities like running or biking for extended periods. Previous research has found links between high cardiorespiratory fitness levels and a lower risk of colon cancer, and a reduced risk of prostate and lung cancer mortality.

Yet few studies have looked at the impact of aerobic fitness on multiple types of cancer.

However, in a new observational study published on August 15 in the British Journal of Sports Medicine, researchers used data from over a million Swedish men who enlisted in the military from 1968–2005 to investigate whether cardiorespiratory fitness influenced the risk of 18 different cancer types.

When the participants enlisted, they were between 16 and 25 years of age and underwent assessments that measured muscle strength, cardiorespiratory fitness, height, body mass index (BMI), and blood pressure.

The assessments showed that 365,874 men had a low level of cardiorespiratory fitness, 519,652 had a moderate level, and 340,952 had a high level.

The researchers observed that those in the low fitness category were more likely to have obesity and alcohol or substance misuse. They were also more apt to have parents with lower education levels.

During an average 33-year follow-up, 84,117 participants developed at least one of the 18 cancer types the team investigated. After analyzing the data, the scientists found a linear association between higher cardiorespiratory fitness levels and a lower risk of developing nine types of cancer.

Specifically, the study found aerobic fitness at a young age was associated with a:

• 5% lower risk of rectal cancer
• 12% lower risk of pancreatic cancer
• 18% lower risk of bowel cancer
• 19% lower risk of head and neck cancer
• 20% lower risk of kidney cancer
• 21% lower risk of stomach cancer
• 39% lower risk of esophageal cancer
• 40% lower risk of liver cancer
• 42% lower risk of lung cancer

However, the researchers also discovered associations between high cardiorespiratory fitness and a 7% increased risk of prostate cancer and a 31% heightened risk of skin cancer.

The study authors speculate that the heightened risk of skin cancer could be due to exposure to sunlight while exercising outdoors. While the prostate cancer risks likely reflect increased access to prostate cancer screening.

Despite these encouraging results, the research had several limitations. For example, the study doesn't prove that high aerobic fitness causes a lowered risk of these types of cancer — it only found an association. In addition, the scientists did not have data about the participants' lifestyles, including diet, alcohol use, and smoking status. They also could not determine whether the participants' fitness levels changed over time.

Moreover, the research looked at men only, so it's unknown if the results would be similar in women.

Nonetheless, the study authors say the results add more evidence that increasing cardiorespiratory fitness at a young age may improve health outcomes. In addition, they suggest these findings could inspire public health policymakers to develop interventions to improve aerobic fitness levels in young people.