Purpose: This study aimed to test whether incident kidney cancer risk is associated with exercise energy expenditure (i.e., metabolic equivalents, 1 MET) when calculated from distance walked or run.
Methods: Hazard ratios (HR) and 95% confidence intervals (95% CI) from Cox proportional hazard analyses of self-reported physician-diagnosed incident kidney cancer versus MET-hours per week in 91,820 subjects recruited between 1991 and 1993 (7.7 yr follow-up of 42,833 subjects) and between 1998 and 1999 (6.4 yr follow-up of 33,053 subjects) as part of the National Runners’ Health Study and between 1998 and 1999 as part of the National Walkers’ Health Study (5.7 yr follow-up of 15,934 subjects).
Results: Fifty-two incident cancers were reported. Age- and sex-adjusted risk declined 1.9% per MET-hour per week run or walked (HR = 0.981, 95% CI = 0.964–0.997, P = 0.02). Compared with walking or running below guidelines levels (<7.5 MET·h·wk−1), the risk for incident kidney cancer was 61% lower for meeting the guidelines (HR = 0.39, 95% CI = 0.11–1.08, P = 0.07 for 7.5–12.5 MET·h·wk−1), 67% lower for exercising one to two times the recommended level (HR = 0.33; 95% CI = 0.15–0.72, P = 0.005 for 12.6–25.1 MET·h·wk−1), and 76.3% lower for exercising two times or more the recommended level (HR = 0.24, 95% CI = 0.11–0.52, P = 0.0005 for ≥25.2 MET·h·wk−1). Incident kidney cancer risk also increased in association with baseline body mass index (P = 0.002), smoking (P = 0.02), and hypertensive (P = 0.007) and diabetes medication use (P = 0.01); however, exercise-associated reductions in kidney cancer risk persisted for 12.6–25.1 MET·h·wk−1 (HR = 0.35, P = 0.01) and ≥25.2 MET·h·wk−1 (HR = 0.29, P = 0.004) vis-à-vis <7.5 MET·h·wk−1 when also adjusted for body mass index, hypertension, diabetes, and pack-years smoked.
Conclusion: Running and walking may reduce incident kidney cancer risk independent of its other known risk factors.
Donner Laboratory, Life Sciences Division, Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, CA
Address for correspondence: Paul T. Williams, Ph.D., Donner Laboratory, Life Sciences Division, Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, CA 94720; E-mail: email@example.com.
Submitted for publication March 2013.
Accepted for publication July 2013.