Midlife Cardiorespiratory Fitness And Later Life Cancer Outcomes Among Women

PURPOSE: Higher midlife cardiorespiratory fitness (CRF) is linked to reduced risk of cancer and improved survival after cancer, but most evidence comes from men. Studies in women often analyze all-site cancer only and frequently rely on submaximal tests or non-exercise algorithms, which can overestimate CRF in those with lower fitness. This study investigated associations between midlife CRF and site-specific cancer incidence and survival among women in later life. METHODS: The study included 8,496 women from the Cooper Center Longitudinal Study who completed a preventive medical exam before age 65 at the Cooper Clinic (1971-2018) and later enrolled in Medicare (1999-2019). A subsample (n = 3,171; 2000-2018) with more complete data on menopausal status was used to assess menopause as an effect modifier. CRF was estimated with a maximal treadmill test. A total of 1092 diagnoses of breast, colorectal, endometrial, and lung cancer were identified from the Chronic Conditions Warehouse (mean 7.8 years of surveillance), with 247 deaths after diagnosis of one of the included cancers (mean 6.4 years of surveillance after cancer). Illness-death models estimated hazard ratios (HR) and 95% confidence intervals (CI) for associations of CRF with cancer incidence and mortality after cancer, adjusting for age, exam year, current smoking, BMI, cholesterol, glucose, and systolic blood pressure. RESULTS: At baseline, participants were a mean age of 48.7 (SD: 9.0) years, 96.4% were White, and the average CRF was 9.1 (SD: 1.9) METs. In the full sample, CRF was not associated with the incidence of breast, colorectal, endometrial, or lung cancer. However, each 1-MET increase in CRF was related to a 21% lower risk of death after lung cancer (HR: 0.79, 95% CI: 0.65, 0.94). In the menopause subsample, premenopausal CRF appeared protective against breast cancer (HR per MET: 0.87, 95% CI: 0.73, 1.03), though the association was not statistically significant; postmenopausal CRF was not associated with breast cancer risk (HR per MET: 1.01, 95% CI: 0.91, 1.13). CONCLUSIONS: Higher CRF in midlife was associated with improved survival after lung cancer, and premenopausal CRF may reduce breast cancer risk in later life. Further research is needed to explore sex-based differences in the relationship between CRF and cancer outcomes.