Abstract
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. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1038/s41598-025-29410-7.