Currently, cardiovascular disease is the leading cause of death, and dyslipidaemia is an independent and modifiable major risk factor. Previous studies on shift work with dyslipidaemia and hair cortisol concentration (HCC) have yielded conflicting results. The aim of this study was to clarify the association between shift work, dyslipidaemia, and HCC. We further explored the mediating effect of HCC.
(2022) 22:1634 Zhu et al BMC Public Health https://doi.org/10.1186/s12889-022-14038-3 Open Access RESEARCH The relationships of shift work, hair cortisol concentration and dyslipidaemia: a cohort study in China Lejia Zhu†, Yu Zhang†, Lin Song, Ziqi Zhou, Jin Wang, Yangmei Wang, Lingli Sang, Jing Xiao and Yulong Lian* Abstract Background: Currently, cardiovascular disease is the leading cause of death, and dyslipidaemia is an independent and modifiable major risk factor Previous studies on shift work with dyslipidaemia and hair cortisol concentration (HCC) have yielded conflicting results The aim of this study was to clarify the association between shift work, dyslipidaemia, and HCC We further explored the mediating effect of HCC Methods: In this cohort study, baseline data were collected from participants in May 2013 The cohort included 2170 participants- 1348 shift workers and 822 non-shift workers- who were followed up for 6 years with four questionnaire surveys from July 2014, October 2015, and May to December 2019 Hair samples were collected from 340 participants during the baseline period for HCC testing with an automated radioimmunoassay Dyslipidaemia was defined using the National Cholesterol Education Program Adult Treatment Panel III diagnostic criteria Results: Shift workers had a higher risk of dyslipidaemia than workers on the fixed day shift (two-shift RR = 1.408, 95% CI: 1.102–1.798; three-shift RR = 1.478, 95% CI: 1.134–1.926; four-shift RR = 1.589, 95% CI: 1.253–2.015) Additionally, shift workers had higher HCC levels than fixed day shift workers, with geometric mean concentration (GMC) ± geometric standard difference (GSD) = 2.625 ± 2.012 ng/g, two-shift GMC ± GSD = 3.487 ± 1.930 ng/g, threeshift GMC ± GSD = 2.994 ± 1.813 ng/g, and four-shift GMC ± GSD = 3.143 ± 1.720 ng/g High HCC was associated with a high incidence of dyslipidaemia After controlling for confounding factors, this study showed that HCC played a role in mediating dyslipidaemia in shift workers and accounted for 16.24% of the effect Conclusions: Shift work was linked to increased risk of dyslipidaemia compared with fixed day shift work Higher HCC was associated with a higher prevalence of dyslipidaemia HCC had a significant mediating effect on dyslipidaemia in shift workers Keywords: Shift work, Dyslipidemia, Hair cortisol concentration, Mediating effect † Lejia Zhu and Yu Zhang are co-first author † Lejia Zhu and Yu Zhang are contributed equally to this work *Correspondence: lianyulong444@163.com Department of Epidemiology and Medical Statistics, School of Public Health, Nantong University, Se Yuan Road, No 9, Nantong 226001, Jiangsu, China Introduction The anciently high prevalence of dyslipidemia has been increasing in many developed and developing countries [1] It exceeded 30% of adults in western countries [2] An online survey of 65,892 people in Italy found that about 60% of participants had high blood cholesterol levels [3] In the German population aged 18 to 79 years, the prevalence of dyslipidemia was 56.6% in men and 60.5% in women [4] In Chinese adults, this was 40.4% [5] © The Author(s) 2022 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/ The Creative Commons Public Domain Dedication waiver (http://creativeco mmons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data Zhu et al BMC Public Health (2022) 22:1634 The number of people doing shift work is probably between 10 and 25% of all employees [6] Shift work has been reported to be associated with dyslipidemia, but published results are inconsistent [6–12] Wu et al [7] found that the number of people with dyslipidemia was much higher in shift work than that in non-shift work, and the difference was statistically significant In a population-based study of 27,485 people, the youngest age group of shift workers was found to have low concentrations of high-density lipoprotein (HDL) cholesterol in both men and women [8], and a cross-sectional study found that shift work was a risk factor for lipid profile disturbances [6] A prospective cohort study [9] reported that shift work with night shifts was associated with increased use of dyslipidemia medications after adjustments (HR = 1.33, 95% CI = 1.12–1.57) Dutheil, Frédéric et al [11] found that shift work, and particularly permanent night shifts, was associated with dyslipidemia However, EunKyo Kang [10] found that there were no significant differences in patients with dyslipidemia according to the type of shift In a longitudinal study it was reported that the changes in total lipids (generic term for various lipid components in serum) caused by shift work were not statistically significant [12] The influence of shift work on the incidence of dyslipidemia might be related to the irregular diet [13, 14] and high-sugar diet [15] caused by shift work Moreover, sleep deprivation will increases the secretion of ghrelin, a growth-hormone-releasing acylated peptide from the stomach [16], which increases hunger and leads to obesity [17, 18] and dyslipidemia [19, 20] Cortisol is a glucocorticoid hormone in the human hypothalamic-pituitary-adrenocortical (HPA) axis and is considered a retrospective biomarker for various chronic physiological and psychological stress diseases, anxiety, and depression [21] Its secretion also fluctuates with the circadian rhythm [22] HCC was more stable than the cortisol concentrations in blood, urine, and saliva [22] The concentration of hair-like cortisol can be accumulated [23]; it can better reflect the long-term cortisol exposure level of the body [24] Shift work may alter the circadian rhythm of the HPA axis and cause a long-term increase in cortisol concentration [25] Chida and Steptoe [26] reported that the magnitude of the cortisolawakening response was influenced by sleep deprivation Manenschijn et al [27] found that hair cortisol levels were significantly increased in individuals working in shifts, especially in the under 40 year old group (P 5.18 mmol/L, TG > 1.7 mmol/L, and HDL-C