Data set used in the paper titled "Optimising the caffeine nap for counteracting driver sleepiness in CPAP treated obstructive sleep apnoea patients"

This data was collected across three studies to investigate the effectiveness of caffeine, nap opportunity and caffeine nap countermeasures on subjective sleepiness (KSS), objective sleepiness (Alpha and Theta activity) and driving performance (standard deviation of lateral position and out-of-lane events) in a driving simulator.Twenty-one CPAP treated OSA participants (mean age = 59) engaged with a protocol of six laboratory visits: one after a normal night’s CPAP-treated sleep and five after sleep restriction (4 hours CPAP-treated sleep), driving a monotonous simulated scenario before and after a countermeasure.Participants were asked to visit the lab a total of six times. Before each visit, participants completed a sleep diary and wore an actiwatch to record how much sleep was obtained the night before each drive. Participants were also asked to avoid caffeine before each visit.Visit 1 served as both a screening visit to test for signs of simulator sickness and to familiarise participants with the procedure, as well as an alert condition in which participants’ sleep was not restricted the night before. Visit 1 occurred at 10am for all participants to ensure that they were not subject to fatigue due to circadian lows in the afternoon.During visit 1, participants were given detailed information about the study, and they provided informed consent to take part in the research. They were then presented with a simulator sickness questionnaire (SSQ) [38] before the study to check for any signs of sickness before starting. They were then taken to the simulator to complete a short practice drive (~5 minutes) to check for any signs of simulator sickness. If the participant experienced no simulator sickness and was happy to continue with the study, they were taken out of the car and had the electrodes attached for polysomnography. Following the attachment of the electrodes, participants were taken back to the car to complete an alert drive lasting 45 minutes.Visits 2-5 involved participants returning to the lab following a night of sleep restriction to 4 hours. This was measured by actigraphy, the sleep diary, and by checking how long the CPAP device was used the night before the study. In these visits, participants first completed a 30-minute pre-intervention drive in the simulator (using the same road as visit 1) before completing one of the four caffeine and nap interventions. The individual conditions were: drinking one can of iced coffee, drinking two cans of iced coffee, having a 15-minute nap, or a 30-minute nap opportunity in the car. This was followed by a 45-minute post-intervention drive. The second drive commenced immediately following the intervention to replicate an approach that drivers might take in the real world. Consequently the duration of time spent not driving while the intervention took place varied between conditions. The order of these visits was counterbalanced using a blocked design such that participants always completed the caffeine conditions consecutively, and the nap conditions consecutively. This gave a total of four counterbalance orders.Study 1 compared two cans of coffee (255mg caffeine) compared to one can (127.5mg)Study 2 compared a 30min nap opportunity with a 15min nap opportunity.Study 3 compared driving when alert, when sleepy (sleep restriction to 4 hours) before and after a caffeine nap (CN). The CN was made up of 2 cans of coffee and a 15min nap opportunity© the authors