Table 1a.

Objective sleep measurement methods.

Sleep or circadian variable	Definition
Polysomnography (PSG)	Recording of electrical activity during sleep from multiple sources – typically including electroencephalography, electrooculography, electromyography, and electrocardiogram respectively monitoring electrical activity in the brain, eyes, muscles and heart. May also include respiratory indicators or other measurements.
Actigraphic monitoring	Continuous activity monitoring, usually carried out over several days via a device worn on the wrist, allows objective measurement of sleep-wake patterns (time to sleep, time to wake, sleep onset, night wakings etc.)
Melatonin concentration	Melatonin production rises during evening and peaks during the night. Irregular peaks or reduced amplitude in melatonin cycles are associated with circadian rhythm sleep-wake disorders (Table 2). Regular collection of saliva or urine allows measurement of concentrations of melatonin throughout the day, which can be combined with actigraphic monitoring to assess circadian functioning