The effect of bright light therapy on sleep and circadian rhythms in renal transplant recipients: a pilot randomized, multicentre wait-list controlled trial

This study assessed the effect and feasibility of morning bright light therapy (BLT) on sleep, circadian rhythms, subjective feelings, depressive symptomatology and cognition in renal transplant recipients (RTx) diagnosed with sleep-wake disturbances (SWD). This pilot randomized multicentre wait-list controlled trial included 30 home-dwelling RTx randomly assigned 1:1 to either 3 weeks of BLT or a wait-list control group. Morning BLT (10 000 lux) was individually scheduled for 30 min daily for 3 weeks. Wrist actimetry (measuring sleep and circadian rhythms), validated instruments (subjective feelings and cognition) and melatonin assay (circadian timing) were used. Data were analysed via a random-intercept regression model. Of 30 RTx recipients (aged 58 ± 15, transplanted 15 ± 6 years ago), 26 completed the study. While BLT had no significant effect on circadian and sleep measures, sleep timing improved significantly. The intervention group showed a significant get-up time phase advance from baseline to intervention (+24 min) [(standardized estimates (SE): -0.23 (-0.42; -0.03)] and a small (+14 min) but significant bedtime phase advance from intervention to follow-up (SE: -0.25 (-0.41; -0.09). Improvement in subjective feelings and depressive symptomatology was observed but was not statistically significant. Bright light therapy showed preliminary indications of a beneficial effect in RTx with sleep-wake disturbances. (ClinicalTrials.gov number: NCT01256983).