Cardiorespiratory fitness associated with 40% reduction in risk of 9 cancers

UNITED STATES: A substantial long-term study published online in the British Journal of Sports Medicine finds that having strong cardiorespiratory fitness while you're young is related to a 40 per cent lower risk of developing 9 specific cancers later in life, at least in men. Cancers of the head and neck, food pipe (oesophagus), stomach, pancreas, liver, colon, kidney, and lung are among them.

Cardiorespiratory fitness refers to a person's capacity to conduct aerobic exercise for extended periods of time, such as running, cycling, swimming, or even climbing stairs. It has been linked to a decreased incidence of various cancers, although few big, long-term studies of multiple cancer sites have been reported. As a result, the researchers drew on connected Swedish registry data up to the end of 2019, which covered background information, medical diagnoses, and mortality for conscripts who began their military duty between 1968 and 2005.G

At the start of their stint, when they were aged between 16 and 25, conscripts underwent a standard battery of assessments. These included height, weight (BMI), blood pressure, muscular strength and cardiorespiratory fitness. Conscripts with a low level of cardiorespiratory fitness were slightly more likely to be obese, more likely to have a history of alcohol and substance misuse and to have parents with lower educational attainment than conscripts with a higher fitness level.

In all, 365,874 conscripts had a low level of cardiorespiratory fitness; 519,652 had a moderate level; and 340,952 had a high level. The final analysis included more than 1 million men (1,078,000), 84,117 (7 per cent) of whom subsequently developed cancer in at least one site during an average monitoring period of 33 years.

Compared with men with a low level of fitness at conscription, higher cardiorespiratory fitness was linearly associated with a lower risk of developing specific types of cancer. It was associated with a 5 per cent lower risk of rectal cancer (2337); a 12 per cent lower risk of pancreatic cancer (1280); an 18 per cent lower risk of bowel cancer (3222); a 19 per cent lower risk of head and neck cancer (2738 men); a 20 per cent lower risk of kidney cancer (1753); a 21 per cent lower risk of stomach cancer (902); a 39 per cent lower risk of food pipe cancer (689); a 40 per cent lower risk of liver cancer (1111); and a 42 per cent lower risk of lung cancer (1635).

But higher cardiorespiratory fitness was also associated with a 7 per cent heightened risk of prostate cancer (14, 232 men) and a 31 per cent heightened risk of skin cancer (23, 064). Prostate cancer screening and exposure to sunlight might account for these findings, suggest the researchers. This is an observational study, so no firm conclusions can be drawn about cause and effect, and the researchers acknowledge that they didn’t have full data on other potentially influential lifestyle risk factors, such as diet, alcohol intake, and smoking, in particular. Nor were they able to track any changes in cardiorespiratory fitness over time or gather any genetic information on participants.

Nevertheless, their findings are reflected in the American Society of Clinical Oncology guidelines on exercise during cancer treatment, they point out. And they concluded: “This study shows that higher fitness in healthy young men is associated with a lower hazard of developing 9 out of 18 investigated site-specific cancers, with the most clinically relevant hazard rates in the gastrointestinal tract.

“These results could be used in public health policymaking, further strengthening the incentive for promoting interventions aimed at increasing [cardiorespiratory fitness] in youth.