Association between rotating night shift work and risk of coronary heart disease among women
Published Date:Apr 26 2016
Pubmed Central ID:PMC5102147
Funding:UM1 CA176726/CA/NCI NIH HHS/United States
R01HL034594/HL/NHLBI NIH HHS/United States
R01 HL034594/HL/NHLBI NIH HHS/United States
UM1 CA186107/CA/NCI NIH HHS/United States
UM1CA186107/CA/NCI NIH HHS/United States
UM1CA176726/CA/NCI NIH HHS/United States
5R01OH009803/OH/NIOSH CDC HHS/United States
Prospective studies linking shift work to coronary heart disease (CHD) have been inconsistent and limited by short follow-up.
Determine whether rotating night shift work is associated with CHD risk.
Design, Setting and Participants
Prospective cohort study of 189,158 initially healthy women followed over 24 years in the Nurses' Health Studies (NHS (1988-2012): N=73,623, and NHS2 (1989-2013): N=115,535).
Questionnaire-based lifetime history of rotating night shift work (≥3 night shifts/month, plus day and evening shifts) at baseline; also updated every 2-4yrs in NHS2.
Main Outcomes and Measures
Incident CHD, i.e. non-fatal myocardial infarction, CHD death, angiogram-confirmed angina pectoris, coronary artery bypass grafting (CABG), stents, and angioplasty.
During follow-up, 7,303 incident CHD cases in NHS (mean age at baseline: 54.5yrs) and 3,519 in NHS2 (34.8yrs) occurred. In multivariable adjusted Cox proportional hazards models, increasing years of baseline rotating night shift work were associated with a significantly higher CHD risk in both cohorts (NHS: age-standardized incidence rate (IR)<5yrs per 100,000 person-years=435.1, hazard ratio (HR)<5yrs=1.02, 95% confidence interval (CI)=0.97-1.08, IR5-9yrs=525.7, HR5-9yrs=1.12, 95%CI=1.02-1.22, IR≥10yrs=596.9, HR≥10yrs=1.18, 95%CI=1.10-1.26; Ptrend<0.001; NHS2: IR<5yrs=130.6, HR<5yrs=1.05, 95%CI=0.97-1.13; IR5-9yrs=151.6, HR5-9yrs=1.12, 95%CI=0.99-1.26; HR≥10yrs=178.0, HR≥10yrs=1.15, 95%CI=1.01-1.32; Ptrend=0.01), compared to women who never worked rotating night shifts (NHS: IRnever=425.5, NHS2: IRnever=122.6). In NHS, the association between duration of rotating night shift work and CHD was stronger in the first half of follow-up (IR<5yrs=382.4, HR<5yrs=1.10, 95%CI=1.01-1.21, IR5-9yrs=483.1, HR5-9yrs=1.19, 95%CI=1.03-1.39, IR≥10yrs=494.4, HR≥10yrs=1.27, 95%CI =1.13-1.42, Ptrend <0.001) than in the second half (IR<5yrs=424.8, HR<5yrs=0.98, 95%CI=0.92-1.05, IR5-9yrs=520.7, HR5-9yrs=1.08, 95%CI=0.96-1.21, IR≥10yrs=556.2, HR≥10yrs=1.13, 95%CI =1.04-1.24, Ptrend=0.004, PInteraction=0.02), suggestive of waning risk after cessation of shift work. Longer time since quitting shift work was associated with decreased CHD risk among ever shift workers in NHS2 (Ptrend<0.001).
Conclusions and Relevance
Among women who worked as registered nurses, longer duration of rotating night shift work was associated with a statistically significant, but small absolute increase in CHD risk. Further research is needed to explore whether the association is related to specific work hours and individual characteristics.
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