O077 The Impact of Breaking up sitting during Simulated Nightshifts on Driving Performance during the Commute Home

Abstract Introduction The commute home from a nightshift is associated with increased accident risk. Driving performance strategies typically occur immediately before or during the commute, such as napping and caffeine. It is unknown whether strategies that target alertness throughout the nightshift could impact the commute home. Breaking up sitting with walking is an effective strategy to improve alertness during dayshifts. This study investigated the impact of breaking up sitting during the nightshift on driving performance post-shift. Method 41 adults (age M±SD: 24.4±4.6 years; 21 females) participated in a 7-day laboratory study, with 5 nightshifts (2200-0630). Participants were randomly allocated to: Breaking up sitting (BUS; n=21) or Sedentary (SED; n=20). Every 30-min during the nightshift BUS participants completed 3-min bouts of light-intensity walking, while SED participants remained sitting. At 2130 (pre-shift) and 0700 (post-shift) participants completed a 20-min simulated drive and the Karolinska Sleepiness Scale. Results Linear mixed models revealed a significant interaction between time (pre- or post-shift) and nightshift on driving performance and sleepiness, such that there was increased lane variability (p=0.03), speed variability (p<0.05), and sleepiness (p<0.05) post-shift compared to pre-shift, with performance worse on the first nightshift. There were no significant 2-way or 3-way interactions between condition (BUS or SED), time, or nightshift. Discussion Breaking up sitting with light-intensity walking did not improve performance for the commute home. However, given that breaking up sitting did not increase risk on the commute home, and it has benefits for cardiovascular health, it is an important strategy to promote to nightshift workers.