Expectation of a loud alarm is not associated with changes in on-call sleep in the laboratory

Anecdotally, people report disturbed sleep when ‘on-call’ and field data suggest that being on-call, even if ‘undisturbed’, may result in sleep disturbance. We investigated changes to sleep when expecting a loud, on-call alarm as compared to sleep when not expecting an alarm. Healthy males (n = 16) aged 24.6 ± 4.0 years took part in a simulated on-call scenario involving two conditions; Control and on-call. Prior to the Control sleep, participants were told that they would not be woken during the night, prior to the on-call sleep, participants were told to expect a loud alarm during the night, following which they were to complete 2 h of testing. Sleep was measured using a standard 5-channel polysomnograhic (PSG) montage. Sleep diaries were used to compare subjective variables; pre- and post-sleep sleepiness and sleep quality. There was no significant difference between the two nights for any of the PSG variables, except for REM where there was a non-significant trend (p = .051) with 8 min more REM on the on-call night. Participants were significantly sleepier following the on-call night, likely due to the earlier wake time (p < .01). These results question whether simply being on-call is disruptive to sleep or whether disruption is connected to other factors such as likelihood of being called, worry about missing the call and/or the events that follow.