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We aimed to characterise objective and subjective sleepiness and driving events during short work commutes and examine the impact of circadian and homeostatic factors across different shift types in a shift worker population. Thirty-three nurses were monitored for 2 weeks over day (07:00-15:30), evening (13:00-21:30) and night shifts (21:00-07:30). Sleep was measured via daily sleep logs and wrist actigraphy. Driving logs were completed for each work commute, reporting driving events and a pre-drive Karolinska Sleepiness Scale (KSS). Ocular data from a subset of participants (n=11) assessed objective sleepiness using infrared oculography during commutes. Circadian phase was assessed at 3 time-points via urinary 6-sulphatoxymelatonin (aMT6s) collected over 24-48 hours. Subjective and objective sleepiness and sleep-related and hazardous driving events significantly increased following night shift compared to pre-shift. There were significant shift differences with KSS, sleep-related and inattention-related events highest during the post-night shift commute, compared to day and evening shifts. Sleep-related events were highest following the first night shift, whilst inattention-related events were most frequent after consecutive night shifts. KSS, sleep-related and hazardous events were increased during drives following ≥16h of wakefulness. KSS and sleep-related events increased during drives within ±3h of aMT6s acrophase. An interaction between homeostatic and circadian processes was observed, with KSS and sleep-related events highest within ±3h of acrophase, when wakefulness was ≥16h. In naturalistic conditions subjective and objective sleepiness and driving events are increased following night shifts, even during short (~30 minute) commutes and exacerbated by an interaction between circadian phase and duration of wakefulness. |
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