No abstract

Widespread co-occurrence of musculoskeletal pain symptoms was common among female kitchen workers with slight predominance in the upper body.

SUMMAR Y Sleep in shift work has been studied extensively in regular shift systems but to a lesser degree in irregular shifts. Our main aim was to examine the sleep-wake rhythm in shift combinations ending with the night or the morning shift in two irregular shift systems. Three weeks' sleep ⁄ work shift diary data, collected from 126 randomly selected train drivers and 104 traffic controllers, were used in statistical analyses including a linear mixed model and a generalized linear model for repeated measurements. The results showed that the sleep-wake rhythm was significantly affected by the shift combinations. The main sleep period before the first night shift shortened by about 2 h when the morning shift immediately preceded the night shift as compared with the combination containing at least 36 h of free time before the night shift (reference combination). The main sleep period before the night shift was most curtailed between two night shifts, on average by 2.9 and 3.5 h among the drivers and the controllers, respectively, as compared with the reference combination. Afternoon napping increased when the morning or the day shift immediately preceded the night shift, the odds being 4.35-4.84 in comparison with the reference combination. The main sleep period before the morning shift became 0.5 h shorter when the evening shift preceded the morning shift in comparison with the sleep period after a free day. The risk for dozing off during the shift was associated only with the shift length, increasing by 17 and 35% for each working hour in the morning and the night shift, respectively. The results demonstrate advantageous and disadvantageous shift combinations in relation to sleep and make it possible to improve the ergonomy of irregular shift systems.

Sleepiness and fatigue are frequent problems in railway transportation with occasional monotony and irregular shift schedules. This study aimed at (1) studying the prevalence of severe sleepiness in shifts and (2) examining which shift and sleep‐related factors were associated with the occurrence of severe sleepiness in an irregular shift system. A total of 126 randomly selected male train drivers (Tdrs) and 104 railway traffic controllers (Tcos) were investigated using questionnaires and sleep–wake diaries. A sleep diary was used to collect information on sleepiness at work and sleeping times during the 21 consecutive days of the study. The prevalence of severe sleepiness at work (i.e. Karolinska Sleepiness Scale 7 or higher) was modelled by a logistic regression analysis for repeated measurements (GEE) using different shift schedule related factors and sleep length as explanatory variables. Severe sleepiness was reported in 49% (Tdrs) and 50% (Tcos) of the night shifts and in 20% (Tdrs) and 15% (Tcos) of the morning shifts. The odds ratios showed that the risk for severe sleepiness was 6–14 times higher in the night shift and about twice as high in the morning shift compared with the day shift. Age affected the two occupational samples differently: with Tdrs increased age was associated with an additional 8% reduction of risk for severe sleepiness for each year of age, while the Tcos did not show any age dependency. Shift length increased the risk by 15% for each hour of the shift and main sleep period decreased the risk by 15% for each hour of the main sleep. The risk of severe sleepiness was not consistently related to the time‐off period before the shifts. The results indicate that adjustments for shift timing, length and off‐duty time, in addition to actions aiming at extending the main sleep period, would probably decrease severe sleepiness in railway transportation.

The present study examined the occurrence of sleepiness in various shift combinations ending with a night or morning shift. Three weeks' sleep/work shift diary data, collected from 126 randomly selected train drivers and 104 traffic controllers, were used in statistical analyses. The occurrence of sleepiness at work (i.e., Karolinska Sleepiness Scale 7 or higher) was tested with a generalised linear model with repeated measurements including explanatory factors related to shifts, sleep, and individual characteristics. The prevalence of severe sleepiness varied between 25% and 62% in the combinations ending with a night shift and between 12% and 27% in the combinations ending with a morning shift. The occurrence of sleepiness did not, however, systematically vary between the shift combinations in either case. An increased risk for sleepiness was associated with high sleep need and long shift duration in the night shift and with high sleep need, short main sleep period, long shift duration and an early shift starting time in the morning shift. Also having a child was associated with an increased risk for sleepiness in the night shift. The results suggest that the shift history of 24-36 h prior to the night and the morning shift is not strongly associated with the occurrence of sleepiness at work, but there are other factors, such as shift length and starting time and sleep need, that affect a risk for sleepiness at work.