Cardiorespiratory Fitness And Risk Of Brain Cancer

Abstract

PURPOSE: Brain cancer although uncommon, leads to significant loss in quality of life due to disability and has a high mortality. While prior studies have revealed the cardiorespiratory fitness (CRF) as a risk factor to cancer incidence, such studies specific to brain cancer does not exist due to its rarity. Since CRF is an objective marker of recent physical activity habits and less prone to misclassification, we aimed to assess the relationship between CRF and risk of brain cancer across age groups in a large (N = 580,559) retrospective study. METHODS: Male (N = 542,104) and female (N = 38,455) US Veterans (age 61.3 ± 9.5) completed a symptom-limited exercise treadmill test (ETT) between 1999-2020. None had a history of brain cancer prior to ETT. We established four CRF categories based on age-specific quartiles of peak metabolic equivalents achieved: Least-Fit (n = 122,905); Low-Fit (n = 202,774); Moderate-Fit (n = 116,390); and High-Fit (n = 138,490). Multivariable Cox models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for brain cancer events across CRF categories. RESULTS: During the follow-up period (median = 8.8 years), 813 individuals (age: 63.3 ± 8.3) developed brain cancer (15 events/100,000 person years of observation) at least one-year post-ETT. After adjustment for age, gender, race, body mass index and smoking, the risk of brain cancer was inversely related to CRF. Brain cancer risk was 7% lower for each 1-MET increase in exercise capacity. When CRF categories were considered, comparisons to the Least-Fit category (referent) revealed that Low-Fit individuals had a 30% lower risk of developing brain cancer (HR 0.70; 95% CI: 0.58-0.83). For Moderate-fit, and High-fit individuals the risk was lower by 33% (HR 0.67; 95% CI: 0.55-0.83); and 38% (HR 0.62; 95% CI: 0.50-0.75), respectively. CONCLUSIONS: We observed an inverse and graded association between CRF and brain cancer incidence. These findings suggest that increased physical activity may provide protection against brain cancer and underscore the importance of promoting physical activity for the public.