Italy: Results from a recent study has suggested that chronic lymphocytic leukemia (CLL) might be a long-term consequence of night shift work. However, the researchers did not observe this association with lymphoma in general, nor other B cell lymphoma subtypes. The study appears in the BMJ journal Occupational and Environmental Medicine.
"Conflicting evidence of association was seen between night shift work and CLL risk," Pierluigi Cocco, Department of Medical Sciences and Public Health, University of Cagliari, CAGLIARI, Italy, and colleagues wrote in their study. "The association was not observed with other lymphoma subtypes."

Night shift work is known to disrupt circadian rhythm and cause chronic sleep deprivation. This in turn might increase lymphoma risk through oxidative stress and immunosuppression. Considering this, Dr. Cocco and colleagues aimed to investigate the association between night shift work and risk of lymphoma subtypes in 867 incident cases and 774 controls, the participants of a multicentre Italian study between 2011 and 2017.
For this purpose, occupational experts assessed the lifetime probability of night shift work, the total number of night shifts and years of night shift work among study participants based on questionnaire information. OR for lymphoma and its major subtypes associated with night shift work was calculated with logistic regression after adjusting for age, gender, education, study area, marital status and family history of haemolymphatic cancer.
Based on the study, the researchers found the following:
Ever working night shifts was associated with an increase in the risk of chronic lymphocytic leukaemia (CLL) (OR 1.9), which was highest after a 15–34 years latency.
However, there was not a linear increase in risk by probability of exposure, years of night shift work, nor lifetime number of night shifts whether under rotating or permanent work schedules.
Risk of lymphoma overall, B cell lymphoma (BCL), its major subtypes other than CLL, and other less prevalent BCL subtypes combined did not show an association.
"Our results suggest that chronic lymphocytic leukemia, but not lymphoma in general, nor other B cell lymphoma subtypes, might be a long-term consequence of night shift work," the authors wrote.
"To explore whether specific conditions, such as the individual chronotype and/or the shift-rotating schedule, might differentially affect the immune system further research is warranted, thus modulating the hypothesized effect on the risk of lymphoma and particularly CLL," the authors concluded.
Reference:
Cocco P, Piro S, Meloni F, et alNight shift work and lymphoma: results from an Italian multicentre case–control studyOccupational and Environmental Medicine Published Online First: 13 January 2022. doi: 10.1136/oemed-2021-107845