O1C.3 Nightshift work and risk of lymphoma subtypes

Introduction In 2010, the International Agency for Research on Cancer (IARC) classified ‘Shiftwork that involves circadian disruption’ as a probable human carcinogen (group 2A), based on limited evidence from epidemiological studies and sufficient evidence from experimental animal studies. The epidemiological results were consistent for breast cancer. More recent publications suggested an increase in risk for ovarian and endometrial cancer, prostate cancer, and colorectal cancer. Sleep deprivation is common in shift workers, and it leads to disruption of the transcription of genes implicated in the regulation of the immune response. Objectives As depression of the immune system is a known risk factor for lymphomas, we explored the association between risk of lymphoma subtypes and nightshift work with a case-control study design. Materials and methods Based on the lifetime occupational history available for 323 cases and 463 controls who participated in a case-control study on lymphoma etiology conducted in Sardinia (Italy) in 1998–2006, expert occupational physicians assessed nightshift work for each job entry of each study subject. We calculated risk of major lymphoma subtypes, namely diffuse large B cell lymphoma, follicular lymphoma, chronic lymphocytic leukemia, multiple myeloma and Hodgkin lymphoma, associated with cumulative days of nightshift work with unconditional logistic regression, adjusting by age, gender, and education. Results None of the lymphoma subtypes we investigated showed an association with lifetime cumulative days of nightshift work. Contrary to our expectation, risk of all lymphomas combined tended to decrease with cumulative days of nightshift work. Conclusions Further studies are warranted to investigate in more detail whether sleep deprivation resulting from nightshift work might be implicated in lymphomagenesis. Future investigations should include information on the chronotype of study subjects, the specific shift rotation schedule applied in each workplace, usual hours of sleep per day, and occurrence of daytime sleepiness.