Shift work and the risk for metabolic syndrome among healthcare workers: A systematic review and meta-analysis

ABSTRACT

Shift work, defined as work occurring outside typical daytime working hours, is associated with an increased risk for metabolic syndrome (MetS) due to several biological and environmental changes. The MetS refers to the clustering of several known cardiovascular risk factors, including insulin resistance, obesity, dyslipidemia, and hypertension. This systematic review aims to evaluate the literature on the association between shift work and the risk of MetS in employees of the health sector.

A systematic search was conducted in PubMed, Web of Science, and Scopus databases using appropriate keywords for studies published before September 1, 2021. Eligible studies were those that compared the prevalence of MetS between day and shift healthcare workers; had a cross-sectional, case-control, or cohort study design; provided sufficient data for calculating odds ratios or relative risks with 95% confidence intervals; and articles in English. The Joanna Briggs Institute prevalence critical appraisal tool was used for quality analysis. Risk for MetS and related measures of effect size were retrieved from studies for meta-analysis.

Twelve studies met the criteria for inclusion in the review and meta-analysis. Sample sizes ranged from 42 to 738, and the age range of subjects was between 18 and 65 years. Ten studies demonstrated high methodological quality, while two studies were of average quality.

Ten out of 12 studies in the review demonstrated a higher risk in shift workers for developing MetS than day workers. The pooled OR of MetS in shift workers based on 12 studies was 2.17 (95% CI = 1.31-3.60, P = 0.003; I2 = 82%, P < 0.001). Shift workers exhibited more than a twofold increase in the chance of developing MetS in comparison with day workers.

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From the full-text study:

This study systematically evaluated the evidence for links between shift work and metabolic syndrome (MetS) compared to day-working counterparts.

MetS is a clustering of several cardiovascular risk factors, including insulin resistance, obesity, dyslipidemia and hypertension.

Key findings:

·????????Shift working employees in healthcare are twice as likely to develop MetS compared to dayworkers

·????????Although they couldn’t evaluate the relationship with years of shift working with MetS risk, other research has found a positive dose-response connection (positive as in, as years shiftworking increase so does MetS risk)

·????????These findings support other data that found significantly heightened MetS risk for shift workers across other non-healthcare sectors

·????????Nevertheless, the risk for MetS was greater for people working in healthcare compared to other industries

·????????A key factor in MetS is likely circadian rhythm disruption (chronodisruption); linked with things like impaired glucose and lipid metabolism, adipose tissue function and other things

·????????MetS is also increased by shift employment, sleep deprivation and exposure to bright light at night (when biologically people are normally sleeping)

·????????They highlight some links between obesity and sleep deprivation, and links with Leptin, insulin and impaired fatty acid utilisation. For instance, insulin resistance due to sleep deprivation/chronodisruption amplified by shiftwork results in excessive fatty acid outflow from adipose tissue; these high circulating fatty acids can then accumulate in the liver, skeletal muscle and pancreatic islets (p.7)

·????????They argue that “to safeguard shiftworkers from MetS, health promotion programs as well as other interventional strategies to adopt healthy environmental and behavioral changes should be introduced” and further “organizations should streamline the shift work system with well-designed rotational shift schedules to allow employees to maintain work/life balance” (p8)

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Authors: Sooriyaarachchi, P., Jayawardena, R., Pavey, T., & King, N. A. (2022). Obesity Reviews, e13489.