This study was an extension into an operational setting of previous laboratory work investigating the use of zopiclone and melatonin to facilitate early circadian sleep in transport aircrew. The previous laboratory-based study demonstrated that both melatonin and zopiclone were effective in inducing early circadian sleep without impacting on psychomotor performance after a 7-h sleep period.
In a repeated measures, placebo-controlled protocol, 30 aircrew flew 3 transatlantic missions over which they took each of the 3 medications (placebo, sustained-release melatonin 2 mg, or zopiclone 5 mg) at an early body clock time (17:00) during their first stopover. They wore wrist actigraphs prior to and throughout the missions, took a single dose of their scheduled medication immediately prior to their early circadian bedtime, and completed a sleep questionnaire on arising from their medicated sleep.
The results of the actigraphic data show that relative to placebo, aircrew on melatonin and zopiclone fell asleep more quickly (melatonin: p