Cardiorespiratory fitness and BMI in youth and site-specific cancer mortality in men: A population-based cohort study with register linkage.

10534 Background: There is insufficient evidence on the associations between cardiorespiratory fitness (CRF), body mass index (BMI), and site-specific cancer mortality. Methods: We collected data on all men who underwent military conscription 1968-2005 in Sweden at ages 16-25. CRF was assessed as maximal aerobic workload on a cycle ergometer test and classified as low, moderate, or high. BMI (kg/m 2 ) was classified as underweight ( < 18.5), normal weight (18.5-24.9), overweight (25-29.9), or obesity (≥30). Data was cross-linked on individual level through the Swedish identification number with national registers with high validity for information on cancer mortality. Follow-up was from conscription until death, emigration, or end of follow-up (12/31/2019). Cox regression analyses included CRF and BMI as well as age, year, and site of conscription, parental education, and muscle strength. Primary analyses tested linear trends for CRF and BMI, with effect sizes for categorical comparisons for interpretation. Results: 1,083,738 men were included in the analyses and were followed for a mean of 33 years, during which 8,912 cancer-specific deaths occurred. Lower CRF and higher BMI were linearly associated with any cancer mortality as well as with several site-specific cancer mortalities (table). However, death in some major cancer sites (prostate, CNS) were not associated with CRF or BMI and higher CRF was associated with higher mortality from malignant skin cancer. Conclusions: Higher CRF and lower BMI was associated with lower cancer mortality for some, but not all cancer sites. These results could be used as a further incentive for working with modifiable risk factors in public health. [Table: see text]