. 2022 Apr 1;12(4):e051131. doi: 10.1136/bmjopen-2021-051131

Table 1.

Characteristics of the studies included in systematic review

Author	Study Design	Country and participants	Observation period	Intervention description	Outcome (measures)	Results	Quality assessment rating
Åkerstedt et al, 2001²⁴	Longitudinal intervention study	Sweden, N=63, full-time workers in healthcare service.	36 months	Intervention group (N=41): reduced WWH from 39 hrs/week to 30 hrs/week. Control group (N=22): unchanged working time.	General symptoms, neuropsychological symptoms, working life quality, quality of life, physical activity, sleep	Subjective sleep quality (SSQ), mental fatigue and heart/respiratory symptoms, time for social activity, time for family and friends improved significantly more in the experimental group than in the control group. No significant effects for sickness absence or self-rated health.	Weak
Wergeland et al, 2003²²	Longitudinal intervention study	Norway and Sweden, N=403. Workers in nursing homes, home care services and kindergartens	12–22 months	Intervention group: reduced DWH to 6 hrs/day. Reference group: unchanged working time.	Musculoskeletal disorders, (shoulder-neck and back pain frequency and work-related physical exhaustion) working life quality	A significant interaction was found for neck-shoulder pain and for exhaustion after work in the intervention group. No significant effects were observed in the reference group.	Weak
von Thiele Schwarz et al, 2008²⁰	Longitudinal intervention study	Sweden, N=177 employees from six workplaces at public dental healthcare organisation	12 months	PE group: 2.5 hrs/week of physical activity instead of work time. Reduced work hours group: reduced WWH proportionally to the amount of time worked. Reference group: unchanged working time.	General symptoms, musculoskeletal disorders, working life quality (work-home interference, recovery from work and work ability), physical activity biological markers (blood lipids, neuroendocrine markers, cardiovascular measures)	Physical activity level increased in all three groups but significantly more in PE group. Glucose levels and upperextremity disorders were found to be significantly decreased in the exercise group, while a significant increase in HDL and waist-to-hip ratio was found among those working reduced hours. Participants working reduced hours also had significantly increased total cholesterol, while no changes in LDL-to-HDL ratio were recorded.	Strong
von Thiele Schwarz et al, 2011²¹	Longitudinal intervention study	Sweden, N=177 employees from six workplaces at a public dental healthcare organisation	12 months	PE group: 2.5 hrs/week of physical activity instead of work time. Reduced work hours group: reduced WWH proportionally to the amount of time worked. Reference group: unchanged working time.	On-the-job productivity, working life quality (sickness presenteeism and sickness absenteeism) Objective production levels (administrative records)	Physical activity was significantly associated with an increase in self-rated productivity in terms of increased quantity of work and work-ability and decreased frequency and number of days of sickness absence. No effect was found in the work hours reduction group. In all three groups there was an increase in the number of treated patients per therapist, significantly greater in the reduced work hours group.	Strong
Barck-Holst et al, 2017¹⁸	Longitudinal quasi-experimental trial	Sweden, N=204 A total of 125 participants were deemed as per protocol	18 months	Intervention group: reduced work hours by 25%. Reference group: unchanged working time.	Neuro-psychological symptoms working life quality (demands, control, social support, instrumental manager support, instrumental coworker support, work intrusion on private life) sleep	The intervention group significantly improved restorative sleep, stress, memory difficulties, negative emotion, sleepiness, fatigue and exhaustion on both work days and weekends. Improved demands, instrumental manager support and work intrusion on private life were observed to be significantly higher in the intervention group.	Moderate
Lorentzon 2017²³	Longitudinal intervention study	Sweden, N=124, nurses working in a centre for the elderly	23 months	Intervention group: work-time reduction to 6 hours/day. Reference group: unchanged working time.	General symptoms, musculoskeletal disorders, neuro-psychological symptoms (alertness level, perceived fatigue, energy left at home, feeling calm, perceived stress), working life quality (collaboration and personal development, sick leaves), physical activity sleep	Good perceived health and alertness level, satisfactory level of perceived fatigue. Energy left at home, feeling calm, satisfactory levels of stress, average sleep time increased in intervention group. General symptoms, sleep and musculoskeletal symptoms improved in the intervention group, and dropped in the control group. Collaboration and personal development improved; improved sense of collaboration between nurses. Sick leave increased in the intervention group. No inferential statistics provided.	Weak
Schiller et al, 2017¹⁹	Longitudinal controlled intervention study	Sweden, N=580, workers from 33 workplaces in the public sector	18 months	Intervention group: reduced WWH by 25%. Reference group: unchanged working time.	Sleep perceived stress, feeling of worries	On workdays, the intervention group displayed significantly improved SSQ, decreased sleepiness and perceived stress, less feelings of worries and stress at bedtime when work hours were reduced. Also, a significant 23 min extension of sleep duration was detected. The intervention showed similar positive effects on days off, except for sleep duration.	Strong

HDL, high-density lipoprotein; LDL, low-density lipoprotein; PE, physical exercise; WWH, weekly worked hours.