Association between shift work and obesity among nurses: A systematic review and meta-analysis

Background: The association of shiftwork and the risk of obesity in nurses has been inconsistent in the literature. Objectives: We therefore conducted a systematic review and meta-analysis to quantitatively summarize this association in nurses. Methods: We systematically searched PubMed, Ovid MEDLINE, Cochrane Library, EMBASE and Web of Science from inception until April 2020 for studies that examined the relationship between shift work and obesity in nurses. Pooled odds ratio (OR) was calculated using a fixed- or random-effect model. The quality of each study was evaluated by using the Risk Of Bias In Non-randomized Studies-of Interventions (ROBINS-I) tool. Two researchers independently assessed eligibility and extracted data. The whole process followed the PRISMA statement. Results: We included 11 eligible studies with a total of 74,651 nurses in this study. All of the studies were found to be low or moderate risk of bias according to the ROBINS-I tool. The pooled estimate of the risk of obesity in shift work nurses as compared to non-shift work nurses did not achieve statistical significance (OR = 1.05, 95% CI = 0.97–1.14). However, the risk of obesity was significantly higher in the sub-analysis of night-only shift work nurses (OR = 1.12, 95% CI = 1.03–1.21). In a sub-analysis limited only to the studies of female nurses, the obesity risk was found not to be statistically significant (OR = 1.09, 95% CI = 0.84–1.35). For different regions of study population, shift work was associated with a 36% increased risk of obesity in America (OR = 1.36, 95% CI = 1.30–1.42) and 1% increased risk in Europe and Australia (OR = 1.01, 95% CI = 1.00–1.03). The BMI cut-off for obesity varied in the included studies. When using a cut-off of BMI ≥ 30 kg/m² for obesity, our subgroup analysis shows a positive relationship between obesity and nurse shift work (OR = 1.12, 95% CI = 1.03–1.20). Conclusions: This is the first systematic review and meta-analysis confirming that shiftwork may play a significant role in the development of obesity among nurses, especially in America, Europe and Australia. This was found to be particularly true for night only shift work nurses. Implementation of health policies and a better night shift schedule are needed in the hospital's management to effectively protect nurses from obesity, and the health risks associated with it.