Objectives Evidence on the association between night work and Parkinson’s disease (PD) is sparse and conflicting, calling for more definitive studies.
Methods We included 20 138 female nurses from the Danish Nurse Cohort without PD who at baseline in 1993 and/or 1999 reported their most common current work schedule (day, evening, night, and rotating (a combination of at least two of these)), including information on lifetime cumulative duration (years) of each shift in a 2009 follow-up survey. We obtained information on PD hospital contacts and PD medication until November 2018 via linkage to the Danish National Patient (inpatient from 1977 and outpatient contacts from 1995 onwards) and Prescription Registers starting in 1995. We defined the incidence of PD as the first-ever hospital contact due to PD, or the first-ever redeemed levodopa prescription, whichever came first. We used Cox regression models to calculate HRs and 95% CIs, adjusting for age, smoking status, coffee consumption and use of hormone replacement therapy.
Results We found no significant difference in PD risk among nurses who reported working evening (HR=0.86; 95% CI=0.55 to 1.34), night (HR=1.26; 95% CI=0.79 to 2.02) or rotating shifts (HR=0.83; 95% CI=0.56 to 1.21) at cohort baseline in 1993 or 1999, when compared with permanent day workers. Similarly, persistency of shift work (working the same work schedule for 6+ years) or duration of shift work was not associated with PD risk.
Conclusions Overall, there was little evidence for an association between various shift work schedules including night work and PD in this cohort of middle-aged female nurses.
- occupational health
- public health
- shift work schedule
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Contributors JTJ contributed to the concept and design of the study, conducted statistical analyses and drafted the manuscript. ZJA secured the funding, contributed to the concept and design of the study, and to critical interpretation of the data and the manuscript. JH contributed to the concept and design of the study, and to critical interpretation of the data and the final draft of the manuscript. ES contributed to the design of the study and to critical interpretation of the data, and the final draft of the manuscript. KP contributed to the design of the study and to critical interpretation of the data, and the final draft of the manuscript. LS contributed to the design of the study and to critical interpretation of the data, and the final draft of the manuscript. RGJW contributed to the concept and design of the study, and to critical interpretation of the data and the final draft of the manuscript. MKS provided data from the Danish Nurse Cohort and contributed to the critical review of the manuscript.
Funding This study was funded by The Danish Working Environment Research Fund (Grant no: 22-2017-03).
Competing interests None declared.
Patient consent for publication Not required.
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement No data are available. According to Danish regulation and GDPR, no data are available.
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