This increase can be attributed to factors such as population growth, aging populations, and advancements in medical technology that enable the detection of more cancers. Many of the risk factors contributing to the global cancer burden are modifiable behaviors, including physical activity.
Physical activity (PA) is a behavior that involves movement of the skeletal muscles. However, cardiorespiratory fitness (CRF) is a more objective measure of an individual’s level of moderate-to-vigorous intensity PA.
It is important to note that CRF is influenced not only by physical activity but also by a person’s genetics.
Regular physical activity has been linked to a lower risk of several types of cancer. Despite this, few studies have examined the relationship between CRF and cancer incidence or mortality, especially in large population samples and across different age groups.
Given the projected increase in cancer diagnoses in the coming decades, it is crucial for researchers to investigate preventable risk factors and develop targeted prevention strategies. The objective of this study was to explore the association between midlife CRF and the incidence and mortality of colon, lung, and prostate cancer in men. The study included a large sample of 177,709 men.
The study’s main finding was that higher CRF was associated with a lower risk of colon cancer incidence, lung cancer incidence and death, and prostate cancer death. Some of these findings remained significant even after adjusting for lifestyle habits, comorbidities, and body mass index (BMI).
The association between CRF and lung cancer incidence and mortality was observed primarily in older participants (aged 60 years or older) after adjusting for age. The study estimated that having higher than very low CRF could potentially prevent between 4% and 19% of lung cancer cases and deaths from lung and prostate cancer.
This study is unique in its examination of the association between CRF and both cancer incidence and mortality in the three most common cancers in men. Previous studies on CRF and prostate cancer incidence have yielded inconsistent results. Some studies have reported positive associations, while others found a protective effect limited to younger participants. The study also highlighted the potential influence of higher prostate cancer screening rates in individuals with higher CRF, which may explain the counterintuitive association observed.
The present study, along with a limited number of existing studies, demonstrated the beneficial outcomes associated with higher CRF for lung, colon, and prostate cancer-specific mortality. These associations remained significant even after adjusting for BMI and smoking. The study also conducted a theoretical calculation of prevented cases, suggesting that avoiding very low CRF levels could have prevented a significant proportion of colon cancer cases and deaths from lung and prostate cancer.
The underlying mechanisms explaining the benefits of higher CRF on cancer incidence and mortality are not fully understood. Potential factors include the association between CRF and systemic inflammation, abdominal obesity, dyslipidemia, and insulin sensitivity. Further research is needed to confirm the role of these mechanisms in the effect of CRF on cancer outcomes.
The study also investigated whether the associations between CRF and cancer risk vary across the life course. The results indicated that the lower risk associated with higher CRF for lung cancer incidence and death was primarily evident in participants aged 60 years or older. This highlights the importance of considering a life course approach when examining the relationship between CRF and cancer outcomes.
The clinical implications of these findings emphasize the importance of CRF for reducing cancer incidence and mortality. It is crucial for the general public to understand that while physical activity and CRF are related, PA is the behavior, and CRF is the physiological response within the body. Higher-intensity physical activity has greater effects on CRF and is likely to be more protective against the risk of developing and dying from certain cancers. Moreover, CRF is not only important for cardiovascular disease risk but also for cancer risk.
The study’s strengths include its large sample size and examination of both cancer incidence and mortality in specific cancer types. However, there are some limitations to consider. The study relied on voluntary participation and included only employed individuals, which may limit the generalizability of the findings. Additionally, the use of submaximal tests to estimate cardiorespiratory fitness has inherent limitations compared to direct measurements. The genetic component of both CRF level and cancer risk should also be taken into account. The relatively short follow-up period resulted in a small number of cancer cases and deaths, which could influence the statistical power of the study.
In conclusion, this large prospective cohort study involving Swedish men revealed that moderate and high CRF were associated with a lower risk of colon cancer, and low, moderate, and high CRF were associated with a lower risk of death due to prostate cancer. Only high CRF was associated with a lower risk of death due to lung cancer.
Age played a modifying role in the associations, with higher CRF being associated with a lower risk for lung cancer incidence and death primarily in older participants. These findings suggest that CRF may have a significant role in reducing the risk of developing and dying from certain common cancers in men. Further research, including randomized clinical trials, is needed to confirm these findings. Future studies should also consider examining exposures at different stages of the life course and their associations with cancer incidence and mortality.
reference link : https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2806585