The relationship between the morningness-eveningness questionnaire and incident cancer: A historical clinical cohort study

Objective: We conducted a retrospective cohort study to explore the relationship between chronotype measured by the total Morningness-Eveningness Questionnaire (MEQ) score and incident cancer. Methods: We used clinical and provincial health administrative data on consecutive adults who underwent a Level 1 Polysomnography (PSG) and completed the MEQ between 2010 and 2015 in an academic hospital (Ontario, Canada) and were cancer-free at baseline. Cancer status was derived from the Ontario Cancer Registry. Individuals were followed until death or March 31, 2020. We used multivariable Cox cause-specific regressions to address the research objective. Results: Of 3,004 individuals, 1,781 were analyzed: a median age of 54 years (IQR: 40-64) and 838 (47.1%) men. The median total MEQ score was 63 (IQR: 55-69); 61 (3.4%) were classified as evening (<= 41), 536 (30.1%) as intermediate (42-58), and 1,184 (66.5%) as morning chronotypes (>= 59). Over a median of 7 years (IQR: 5-8), 120 (6.7%) developed cancer. A U-shape relationship was found between the total MEQ score and an increased hazard of incident cancer, controlling for PSG measures of sleep apnea severity and sleep architecture, demographics, and comorbidities. Compared to the median of 63.0, a total MEQ score greater or less than the median was associated with an increased hazard of incident cancer, with the largest effect for those with a total score >= 76 (e.g., HR of a MEQ total score of 78 vs. 63: 2.01, 95% CI: 1.09-3.71). Conclusion: The U-shaped curve may reflect deviations from a standard circadian tendency, which may stress biological systems and influence malignancy risk.