Background It remains unclear whether or which prediagnostic lifestyle and dietary factors influence colorectal cancer (CRC) survival following diagnosis. This study used competing mortality risks analysis to evaluate the association between these factors and CRC survival.
Methods A total of 96 889 cancer-free participants of the Norwegian Women and Cancer Study completed the study’s baseline questionnaire on lifestyle and dietary factors between 1996 and 2004. Of the 1861 women who subsequently developed CRC, 550 had CRC as the cause of death, while 110 had a non-CRC cause of death. We used multiple imputation to handle missing data. We performed multivariable competing mortality risks analyses to determine the associations between prediagnostic lifestyle and dietary factors and CRC survival. Cause-specific HRs were estimated by Cox regression and subdistribution HRs were estimated by the Fine-Gray regression with corresponding 95% CIs.
Results Following multivariable adjustment, a prediagnostic vitamin D intake of >10 μg/day compared with ≤10 μg/day was associated with better CRC survival (HR=0.75, 95% CI 0.61 to 0.92). Other prediagnostic lifestyle and dietary factors showed no association with CRC survival. The corresponding results obtained from cause-specific Cox and Fine-Gray regressions were similar.
Conclusion Our study shows that prediagnostic vitamin D intake could improve CRC survival.
- vitamin D
- colorectal cancer
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Contributors SOO and KBB conceived the initial study idea. SOO carried out the statistical analyses and drafted the manuscript. TB prepared the data and participated in the statistical analyses and critical revision of the manuscript. GS contributed to the statistical analyses and critical revision of the manuscript. KBB contributed to the statistical analyses, drafting, and critical revision of the manuscript. All authors approved the final manuscript version to be published and agreed to be accountable for all aspects of the work.
Funding The publication charges for this article were funded from the publication fund of UiT The Arctic University of Norway. SOO, TB, SG, and KBB were supported by the Faculty of Health of UiT The Arctic University of Norway. The Faculty of Health, UiT The Arctic University of Norway did not contribute to the study design or data analysis nor did it influence the decision to submit the manuscript for publication.
Competing interests None declared.
Patient consent for publication Not required.
Ethics approval The Norwegian Women and Cancer Study obtained approval from the Regional Committee for Medical Research Ethics and the Norwegian Data Inspectorate.
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement Data are available upon reasonable request.
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