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. 2019 Oct;76(10):733-738.
doi: 10.1136/oemed-2019-106016. Epub 2019 Aug 12.

Rotating night shift work and risk of multiple sclerosis in the Nurses' Health Studies

Kyriaki Papantoniou  1 , Jennifer Massa  2 , Elizabeth Devore  3 , Kassandra L Munger  2 , Tanuja Chitnis  4 , Alberto Ascherio  3   5 , Eva S Schernhammer  6   3   5
Affiliations

Rotating night shift work and risk of multiple sclerosis in the Nurses' Health Studies

Kyriaki Papantoniou et al. Occup Environ Med. 2019 Oct.

Abstract

Objectives: Night shift work has been suggested as a possible risk factor for multiple sclerosis (MS). The objective of the present analysis was to prospectively evaluate the association of rotating night shift work history and MS risk in two female cohorts, the Nurses' Health Study (NHS) and NHSII.

Methods: A total of 83 992 (NHS) and 114 427 (NHSII) women were included in this analysis. We documented 579 (109 in NHS and 470 in NHSII) incident physician-confirmed MS cases (moderate and definite diagnosis), including 407 definite MS cases. The history (cumulative years) of rotating night shifts (≥3 nights/month) was assessed at baseline and updated throughout follow-up. Cox proportional hazards models were used to estimate HRs and 95% CIs for the association between rotating night shift work and MS risk adjusting for potential confounders.

Results: We observed no association between history of rotating night shift work and MS risk in NHS (1-9 years: HR 1.03, 95% CI 0.69 to 1.54; 10+ years: 1.15, 0.62 to 2.15) and NHSII (1-9 years: HR 0.90, 95% CI 0.74 to 1.09; 10+ years: 1.03, 0.72 to 1.49). In NHSII, rotating night shift work history of 20+ years was significantly associated with MS risk, when restricting to definite MS cases (1-9 years: HR 0.88, 95% CI 0.70 to 1.11; 10-19 years: 0.98, 0.62 to 1.55; 20+ years: 2.62, 1.06 to 6.46).

Conclusions: Overall, we found no association between rotating night shift work history and MS risk in these two large cohorts of nurses. In NHSII, shift work history of 20 or more years was associated with an increased risk of definite MS diagnosis.

Keywords: circadian disruption; cohort study; multiple sclerosis; night shift work; shift work.

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Conflict of interest statement

Competing interests: ED has received consulting fees from Epi Excellence and Bohn Epidemiology. AA receives research support from the US Department of Defense (Army) (W81XWH-05-1-0117 (PI)) and the NIH (R01 NS045893 (PI), R01 NS047467 (PI), R01 NS48517 (PI), NINDS R01 NS042194 (PI) and R01 NS046635 (PI)).

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