Is Occupational Physical Activity Associated With Cancer Mortality? A 27-year Prospective Study Of 404,249 Norwegian Participants

Cancer, the second leading global cause of death, is influenced by risk factors. However, the impact of occupational physical activity on the mortality risk for specific cancers is unclear. PURPOSE: To examine the association between occupational physical activity and mortality from various cancer sites. METHODS: We included 404,249 participants (aged 18-65 years, 51.8% men) from the Norwegian population-based health examination surveys. Occupational physical activity was measured through a self-reported questionnaire, and categorized into mostly sedentary or requiring walking, walking and lifting, and heavy labour. Fourteen different cancer sites previously associated with leisure-time physical activity (i.e., head and neck, myeloid leukaemia, myeloma, gastric cardia, lung, liver, endometrium, colon, breast, bladder, rectum, oesophagus, prostate, and kidney) were analyzed. Participants were followed from study entry (February 1972 to November 2002) to death or follow-up end (December 31, 2018), whichever came first. Multivariable-adjusted Fine and Gray sub distribution hazard models were used to estimate hazard ratios (HR)s and 95% confidence intervals (CIs). RESULTS: During a median follow-up of 27.4 years (IQR 6.08), 18,150 (4.5%) participants died from cancer. Compared with a sedentary occupation, walking-and-lifting was associated with a 15% lower risk of breast cancer (HR = 0.85, 95%CI = 0.74 to 0.97). Conversely, both the walking and walking-and-lifting groups increased the risk of mortality from kidney cancer by 33 and 35%, respectively (HR = 1.33, 95%CI = 1.06 to 1.66; and HR = 1.35, 95%CI = 1.06 to 1.72, respectively) compared to the sedentary group. No significant associations were found for the other cancer sites or with heavy labour. CONCLUSION: Our study demonstrates a complex interplay between occupational physical activity and cancer mortality. While the walking and lifting group showed a potential protective effect in breast cancer mortality, the walking and walking and lifting groups observed an increased risk for kidney cancer mortality. These findings emphasize the need for nuanced investigations into the specific influences of different occupational activities on cancer outcomes, guiding future research and preventive measures. CC-S is supported by a grant from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska Curie grant agreement No 101028929