Nonexercise estimated cardiorespiratory fitness in relation to incidence of urinary tract, bladder and kidney cancer in the HUNT study.

This study examined the prospective relationships between estimated cardiorespiratory fitness (eCRF) and the incidence of urinary tract cancers, as well as the site-specific incidence of bladder cancer and kidney cancer within a large Norwegian cohort. We included 46,968 cancer-free adults from the second Trøndelag Health Study (HUNT2). eCRF was determined using sex-specific prediction models based on age, waist circumference, resting heart rate, and self-reported physical activity, and further classified into three categories: 20% low, 40% medium, and 40% high. Cause-specific Cox proportional hazard models were applied to estimate hazard ratios (HR) and 95% confidence intervals (CI). Over a median follow-up of 22.2 years, medium and high eCRF were associated with a 13% and 36%, respectively, lower hazard of urinary tract cancers in the total cohort (HR 0.87, 95% CI 0.71–1.05 and HR 0.64, 95% CI 0.51–0.79). Among men, these associations were more pronounced, with a hazard reduction of 17% and 41% in the medium and high eCRF groups, respectively (HR 0.83, 95% CI 0.66–1.04 and HR 0.59, 95% CI 0.46–0.76). High eCRF only was associated with a 34% lower hazard of bladder cancer in men (HR 0.66, 95% CI 0.48–0.90), but not in women. There was a significant inverse dose-response association between eCRF and kidney cancer, particularly among men (P-value for trend < 0.001). In conclusion, eCRF may be a useful marker for evaluating the associations between CRF and urinary tract cancers.