Recurrent on-duty sleepiness and alertness management strategies in long-haul airline pilots

INTRODUCTION: We examined whether long-haul airline pilots without recurrent on-duty sleepiness obtain more prior sleep and use more effective in-flight alertness management strategies than their colleagues with recurrent on-duty sleepiness. METHODS: There were 51 pilots who flew at least twice from Helsinki to Asia. Of them, 44 flew at least twice back to Helsinki following 1 local night. On-duty sleepiness was measured by the Karolinska Sleepiness Scale (KSS), alertness management strategies by a diary, and sleep by a diary and activity monitor. Pilots who rated KSS ≤ 7 on each, some, or none of the flights were classified as "regularly", "sometimes", and "never" sleepy, respectively. This classification was performed separately for the outbound and inbound flights. RESULTS: On the outbound flights, 22% of the pilots were "never", 54% "sometimes", and 24% "regularly" sleepy. For the inbound flights, the respective distribution was 25%, 48%, and 27%. Compared to the "regularly" sleepy group, the "never" sleepy group obtained 54 min more night sleep prior to the outbound flights. For the inbound flights, the respective difference was 1 h 23 min. Also, the "never" sleepy pilots slept 31 min more between days off than the "regularly" sleepy pilots. The results of the in-flight alertness management strategies were mixed. DISCUSSION: The study demonstrates that pilots without recurrent on-duty sleepiness obtain more sleep than their colleagues with recurrent on-duty sleepiness. The result emphasizes the need to investigate whether the sleep of recurrently sleepy pilots can be increased and whether this increase would reduce their on-duty sleepiness.