Light up: an intervention study of the effect of environmental dynamic lighting on sleep–wake rhythm, mood and behaviour in older adults with intellectual disabilities

Background: Evidence-based interventions to improve the sleep–wake rhythm, mood and behaviour in older adults with intellectual disabilities (ID) are limited. Increasing light exposure has been shown to be effective in improving the sleep–wake rhythm, mood, and behaviour in other populations. The current study investigates the effect of installing environmental dynamic lighting in common living rooms of care facilities on sleep–wake rhythm, mood, and behaviour in older adults with ID. Methods: A non-randomised, non-concurrent, multiple baseline study was performed from October 2017 to May 2018. Fifty-four participants [mean (SD) age of 63.42 (8.6) years, 65% female] in six care facilities were included. All participants had three baseline measurements (Weeks 1, 5 and 9). Dynamic lighting was installed in Week 10, after which three intervention measurements took place (Weeks 12, 17 and 24). Sleep characteristics and the sleep–wake rhythm were assessed using actigraphy (GENEActiv). Mood was measured with the Anxiety, Depression and Mood Scale (ADAMS) and behaviour with the Aberrant Behaviour Checklist (ABC). Results: Mixed-effect regression analysis showed a worsening of the primary outcome interdaily stability (P = 0.001). This could be attributed to one care facility, whereas interdaily stability did not change in the other care facilities (P = 0.74). Dynamic lighting led to earlier mid-sleep (P = 0.003) and sleep onset (P <.0001) and improved mood as indicated by lower scores on the ADAMS depression (−0.64 SD, P < 0.001) and social avoidance (−0.47 SD, P = 0.004) subscales. The prevalence of screening above cut-off for depression decreased from 23 to 9.8% (OR =.16, P = 0.003). For behaviour, a decrease was seen in hyperactivity (−0.43 SD, P < 0.001), lethargy (−0.35 SD, P = 0.008) and irritability (−0.33 SD, P <.001) as measured with the ABC. No adverse effects were reported. Conclusion: Installing dynamic lighting in common living areas for older adults with ID improved the mood and behaviour of the residents up to 14 weeks after placement. Integrated dynamic lighting is a promising, undemanding and potentially effective addition to improve mood and behaviour in care organisations for people with ID, but does not seem to do so by improving sleep or sleep–wake rhythms.