Work schedule characteristics and sleepiness – a meta-analysis
这项元分析整合了48项研究，发现夜班期间困倦感显著高于白班，且夜班时长越长困倦感越强，而连续夜班中第一晚的困倦感最高。研究结果对优化轮班制度、降低工伤风险有参考价值。
OBJECTIVES: Sleepiness is a specific aspect of fatigue and considered a key factor linking working time to health and safety outcomes, such as occupational injuries. Therefore, this meta-analysis synthesizes evidence on how specific work schedule characteristics relate to sleepiness. Specifically, we examine how sleepiness varies with: (a) shift type (eg, day versus night), (b) shift length, and (c) the number of consecutive shifts. METHODS: We conducted a systematic literature search across multiple platforms and databases. Only studies that measured sleepiness using the Karolinska Sleepiness Scale were included. Mean effect sizes (Hedges` g) were calculated using random-effects models. RESULTS: The analysis included 48 studies (28 on shift type, 30 on shift length, and 13 on shift number). Compared to day shifts, sleepiness was significantly higher during night shifts and lower during afternoon shifts. Sleepiness increased with shift length during night shifts but showed no consistent pattern during day shifts. Furthermore, sleepiness was highest on the first night shift and decreased over subsequent nights, whereas it remained relatively stable across consecutive day shifts. Due to the low number of studies, results on shift length and shift number were limited or unavailable for afternoon shifts. CONCLUSIONS: Overall, this meta-analysis shows that sleepiness is most pronounced during night shifts, particularly the first in a block. These findings emphasize the importance of circadian and homeostatic factors in shift work. Therefore, shift schedules should be designed to mitigate these heightened risks, for example by allowing sufficient recovery time before and during the first night shift.