Assessment of the impact of shift work on thyroid disorders: a systematic review and meta-analysis

Shift work including night work is a common work pattern worldwide and researchers have no consensus on the impact of shift work on thyroid disorders. We aimed to conduct a meta-analysis to summarize the evidence from published studies to ascertain the impact of shift work on thyroid disorders.

Studies on the link between shift work and thyroid disorders published in Pubmed, Embase, Medline, and Cochrane databases by September 2021 were searched. Newcastle-Ottawa scale was used to assess the quality of included studies. The Mantel-Haenszel statistical method and the inverse-variance statistical method were used to evaluate the pooled results of dichotomous and continuous variables, respectively. Study heterogeneity analysis was performed using I² statistics. Sensitivity analysis was conducted by omitting one study each time and re-calculating the pooled results of the remaining studies.

Seven eligible studies were included in the systematic review and meta-analysis. The results showed that shift work would lead to an increase in TSH (SMD: 0.30; 95%CI: 0.05-0.55; P = 0.02; I² = 64%) and FT4 (SMD: 0.21; 95%CI: 0.02-0.40; P = 0.03; I² = 0%). However, shift work had no clear effect on the risk of positive thyroid autoantibodies (OR: 1.26; 95%CI: 0.62-2.55; P = 0.52; I² = 63%).

Shift work may be associated with abnormal TSH and FT4 levels. Thyroid health is affected in shift workers and it is advisable to remind patients to get good sleep the night before testing thyroid function.