Effect of biologically active light and partial sleep deprivation on sleep, awakening and circadian rhythms in normals.

The effects of biologically active light (BL) on subjective and objective quality of sleep and awakening, as well as circadian rhythms in cortisol, temperature and well-being were studied in 10 hospitalized normal female volunteers as compared with partial sleep deprivation (PSD). After 2 adaption days, three 24-hour periods were recorded before (baseline), during (intervention) and after (recovery) treatment with BL (exposure between 5.00-9.00 p.m. and 6.00-9.00 a.m.; light sensitivity: 2,800 lx at eye level) and PSD (1.30-6.00 a.m.). Somnopolygraphic investigations demonstrated a significant improvement in sleep maintenance both after BL and PSD, while sleep induction improved only after PSD. Subjectively experienced sleep quality increased after both treatments. However, subjective and objective awakening quality (objectivated by means of psychometric test battery) was improved by BL only, while PSD produced no changes or even a deterioration. Cortisol levels tended to be lowered by BL, while the troughs increased after PSD; there was also an earlier rise in cortisol levels after PSD than BL. No significant differences were found in regard to temperature. Subjectively experienced well-being tended to improve after both interventions. Our findings concerning the beneficial effect of BL on objective and subjective quality of sleep and awakening in normals encourages us to initiate a single-dose study with BL in depressed patients.