Night shift work and cardiovascular disease biomarkers in female nurses

• Published in: American journal of industrial medicine 2020-03, Vol.63 (3), p.240-248
• Main Authors: Johnson, Candice Y., Tanz, Lauren J., Lawson, Christina C., Schernhammer, Eva S., Vetter, Céline, Rich‐Edwards, Janet W.
• Format: Article
• Language: English
• Subjects: Adult; Biomarkers; Biomarkers - blood; C-Reactive Protein - analysis; Cardiovascular disease; Cardiovascular diseases; Cardiovascular Diseases - etiology; Cholesterol; Cholesterol - blood; Cholesterol, HDL - blood; Cholesterol, LDL - blood; Chronobiology Disorders - blood; Chronobiology Disorders - etiology; Confidence intervals; C‐reactive protein; Density; Female; Fibrinogen; Fibrinogen - analysis; Heart Disease Risk Factors; High density lipoprotein; Humans; lipids; Long-term effects; Middle Aged; night shift work; Night shifts; Nighttime; Nurses; Nurses - statistics & numerical data; Occupational Diseases - blood; Occupational Diseases - etiology; Post-menopause; Regression analysis; Shift work; Shift Work Schedule - adverse effects; Statins; Statistical analysis; Surveys and Questionnaires; Triglycerides; Triglycerides - blood; women; Work Schedule Tolerance - physiology; Working conditions
• ISSN: 0271-3586; 1097-0274
• DOI: 10.1002/ajim.23079

Background Night shift work is associated with cardiovascular disease, but its associations with cardiovascular disease biomarkers are unclear. We investigated these associations in a study of female nurses. Methods We used data from the Nurses’ Health Study II for total cholesterol, low‐density lipoprotein cholesterol, high‐density lipoprotein (HDL) cholesterol, triglycerides, C‐reactive protein (CRP), and fibrinogen. The sample sizes for our analysis ranged from 458 (fibrinogen) to 3574 (total cholesterol). From questionnaires, we determined the number of night shifts worked in the 2 weeks before blood collection and total years of rotating night shift work. We used quantile regression to estimate differences in biomarker levels by shift work history, adjusting for potential confounders. Results Nurses working 1 to 4 recent night shifts had median HDL cholesterol levels 4.4 mg/dL (95% confidence interval [CI]: 0.3, 7.5) lower than nurses without recent night shifts. However, working ≥5 recent night shifts and years of rotating night shift work were not associated with HDL cholesterol. There was no association between recent night shifts and CRP, but median CRP levels were 0.1 (95% CI: 0.0, 0.2), 0.2 (95% CI: 0.1, 0.4), and 0.2 (95% CI: 0.0, 0.4) mg/L higher among nurses working rotating night shifts for 1 to 5, 6 to 9, and ≥10 years compared with nurses never working rotating night shifts. These associations were attenuated when excluding postmenopausal women and women taking statins. We observed no associations between night shift work and other biomarkers. Conclusions We found suggestive evidence of adverse short‐term and long‐term effects of night shift work on select cardiovascular disease biomarkers.