In a recent study published within the British Journal of Sports Medicine, researchers investigate the connection between changes in adult cardiorespiratory fitness (CRF) and the incidence and mortality of prostate cancer.

Study: Association between change in cardiorespiratory fitness and prostate cancer incidence and mortality in 57,652 Swedish men. Image Credit: Peakstock / Shutterstock.com

Background 

In contrast to other cancers, resembling those affecting the breast, colon, and lungs, wherein preventable risk aspects are well-established, it stays unclear which aspects increase a person’s risk of prostate cancer. The first known risks include developmental aspects and being chubby or obese, particularly for advanced prostate cancer; nevertheless, evidence is proscribed for non-advanced cases.

While physical activity influences various cancer types, its impact on prostate cancer stays unclear, with studies showing mixed results. CRF, which is related to lower systemic inflammation and improved health markers, has been less explored in prostate cancer research. The conflicting findings in CRF and physical activity studies, that are potentially influenced by higher screening rates amongst fitter individuals, emphasize the necessity for added studies. 

Concerning the study 

Researchers analyzed data from the Health Profile Assessment (HPA) database managed by the Health Profile Institute in Stockholm, Sweden. The HPA offered to employees of associated corporations for gratis, included lifestyle questionnaires and a submaximal ergometer CRF test.

CRF was measured using the validated Åstrand test, and participants were categorized into groups based on greater than 3% changes in absolute CRF. Prostate cancer incidence and mortality data were obtained from Swedish national health registries linked to the HPA database.

Statistical evaluation involved Cox proportional hazard regression models to look at the connection between CRF changes and prostate cancer. The researchers adjusted for aspects like age, body mass index (BMI), and smoking. Sensitivity evaluation was conducted to mitigate reverse causality concerns.

All analyses adhered to established statistical assessment guidelines and were performed using R Studio and associated packages.

Study findings 

Between 1982 and 2019, data were acquired from 181,673 men, 58,971 of whom met the factors of getting two or more CRF tests with a minimum gap of 11 months between the tests.

After excluding 1,319 individuals for extreme CRF changes, the sample consisted of 57,652 men with a mean age of 41.4 years and a mean BMI of 26.0 kg/m². Amongst these individuals, 592, or 1% of the study cohort, were diagnosed with prostate cancer, 46 of whom died from the disease.

At baseline, absolutely the and average relative CRF values were 3.12 L/min and 37.4 mL/kg/min, respectively. There was a slight decline in each relative and absolute CRF over a mean of 4.9 years between tests. The follow-up period for incidence evaluation averaged 6.7 years from the last CRF test.

No association between baseline or last-test CRF and prostate cancer risk was observed after adjusting for aspects like age, BMI, and smoking status. Nevertheless, in unadjusted analyses, higher CRF at each time points was inversely related to prostate cancer risk.

Notably, a decrease in absolute CRF was correlated with a better risk of prostate cancer diagnosis. This association remained significant after adjusting for all covariates, including physical activity.

Participants were also categorized by CRF change, which included increased, stable, or decreased +3%, ±3%, and −3%, respectively. Those with increased CRF had a significantly lower risk of cancer incidence as in comparison with the stable group, which remained consistent across most adjusted models.

A sensitivity evaluation that excluded early diagnoses after the last test confirmed the importance of absolute CRF changes on cancer risk. Nevertheless, significant variability across the several models was observed when comparing stable CRF to increased or decreased groups.

The subgroup evaluation, which was stratified by baseline CRF levels, revealed that within the moderate baseline CRF group of 32.4-40.7 mL/kg/min, each standard deviation increase in absolute CRF reduced prostate cancer incidence risk by 16% within the least adjusted model, with significant associations persisting in additional adjusted models. Comparatively, high and low fitness groups showed no significant associations, apart from an inverse relationship within the high fitness group within the least adjusted model, which diminished upon further adjustments.

A positive correlation was also observed between changes in absolute CRF and self-reported physical activity. Nevertheless, changes in CRF didn’t correlate with prostate cancer mortality, as evidenced by the 46 observed deaths within the study.