Association of Evening Shifts, Night Shifts, and Consistent Overtime Exceeding 10 Hours per Day with Sudden Cardiac Arrest: A Case-Control Study

Abstract

Background: We investigated the relationship between employment status, work patterns, and sudden cardiac arrest (SCA). Methods: This was a case-control study from September 2017 through December 2022 involving 17 emergency departments and 9 public health centers. The cases included patients aged 20-79 years with SCA, excluding those with traumatic arrest, terminal illness, pregnancy, unreliable information, or a "Do Not Resuscitate" order. Controls were selected from various health screening centers in Korea. All participants completed structured questionnaires. Propensity score matching was used to ensure comparability by age, sex, and socioeconomic status. Results: Of the 1536 patients enrolled, 116 from the case group were excluded due to missing employment data, leaving 1420 cases and 2304 controls for analysis. Employment was reported by 47.5% of cases and 59.4% of controls. There was no significant difference in the proportion of sole proprietors (20.6% vs. 22.5%, p = 0.39). The case group had a higher proportion of employers (13.2% vs. 6.5%, p < 0.001) and fewer employees (63.3% vs. 69.1%, p = 0.02). Professional roles were more common among controls (23.6% vs. 31.6%, p < 0.001), while labor-intensive jobs were more frequent in cases (27.7% vs. 17.8%, p < 0.001). The case group had more evening and night shifts (odds ratio [OR]: 1.04, 95% confidence interval [CI]: 1.01-1.06; OR: 1.05, 95% CI: 1.01-1.09) and longer workdays (OR: 1.06, 95% CI: 1.03-1.08). Conclusions: SCA patients were more likely to work evening and night shifts and have longer workdays, often exceeding 10 h.

Keywords: cardiac arrest; case–control study; occupations; risk factor.

Figure 1

Inclusion and exclusion flow chart.

Figure 2

Comparison of night/evening shifts and days with over 10 h of work between cases and controls. (A) Number of night shifts per month in the SCA case and healthy control groups. An asterisk (*) denotes an outlier, which is an observation that falls outside the outer fence of the box plot. And a circle (○) denotes an anomaly, which is an observation that falls outside the inner fence of the box plot. (B) Number of evening shifts per month in the SCA case and healthy control groups. (C) Number of days with over 10 h of work per month in the SCA case and healthy control groups. In all analyses, the SCA case group showed a significantly higher frequency, with p-values of 0.014, 0.004, and <0.001, respectively. SCA: sudden cardiac arrest.