Permanent night shifts linked to dyslipidemia, finds study

The reports of the study have been published in Atherosclerosis.

Shift work can be defined as employment in any work schedule that is not a regular daytime schedule (that is, approximately 0900 to 1700). The full spectrum of shift work comprises regular evening or night schedules, rotating shifts, split shifts, on-call or casual shifts, 24-hour shifts, irregular schedules, and other non-day schedules. Shift work has long been known to disrupt circadian rhythm, sleep, and work-life balance; however, flexible work patterns remain a necessary component for a dynamic, diversified industrial economy.

Shift work is associated with an increased risk of hypertension, metabolic syndrome, dyslipidemia, and diabetes mellitus. It has also been well documented that night shifts are linked with myocardial infarction, coronary events, and ischaemic stroke; the relative risks are modest, but population attributable risks are high.

With this in mind, this systematic review and meta-analysis were carried out to determine the impact of shiftwork on dyslipidemia.

A team of researchers under Frédéric Dutheil, attached to the University Hospital of Clermont-Ferrand (CHU), France, designed the study to include data from PubMed, Cochrane Library, Science Direct, and Embase databases without language restriction on 15 February 2020. The studies that describe blood lipids levels or a risk measure in shift workers compared with fixed-day workers (controls) were taken. Differences by study-level characteristics were estimated using stratified meta-analysis by type of shift work, and meta-regression to examine relations between dyslipidemia and demographic, lifestyle, and work characteristics. Estimates were pooled using random-effect meta-analysis.

Results revealed the following facts.

• A total of 66 articles, representing 197,063 workers were analyzed
• . Shift work globally increased the levels of triglycerides (overall SMD = 0.09; 95CI 0.05 to 0.13; p < 0.001), and globally decreased the levels of c-HDL (-0.08; 95CI -0.12 to -0.03; p = 0.001).
• Permanent night shift workers were an at-risk type of shift for dyslipidemia with significantly higher blood levels of total cholesterol (0.22; 95CI 0.01 to 0.42; p = 0.043) and triglycerides (0.18; 0.03 to 0.33; p = 0.017), and significantly lower blood levels of c-HDL (-0.16; 95CI -0.32 to 0.00; p = 0.05).
• Permanent night shift workers were more at-risk for total cholesterol than rotating 3*8 shift workers (Coefficient 0.22; 95CI 0.01 to 0.42; p = 0.038) and rotating 2*12 shift workers (0.24; 0.02 to 0.46; p = 0.037), and more at-risk for triglycerides than rotating day shift workers (0.21; 95CI 0.03 to 0.38; p = 0.023).
• Results were non-significant for c-LDL, nor depending on the type of shifts.

From the results, the researchers highlighted the following observations.

1. Shift work is associated with deleterious cardiovascular effects that might be underline by dyslipidemia.
2. Considering that 20% of the workforce is subjected to shift work, the question of the best shifting rotation is of particular interest.

     3. Permanent night shift workers were the most at-risk type of shift for dyslipidemia with significantly higher blood levels of total cholesterol, triglycerides, and significantly lower blood levels of c-HDL.

     4. Promoting rotating shifts instead of permanent night shifts could be an effective preventive strategy to reduce the cardiovascular risk of shift workers.

"Our current study provides a practical and valuable strengthening of the evidence-base required for preventive health initiatives and workplace reform." wrote the authors.

For the full article click on the link: https://doi.org/10.1016/j.atherosclerosis.2020.08.015

Primary source: Atherosclerosis