Long-term effects of environmental dynamic lighting on sleep–wake rhythm, mood and behaviour in older adults with intellectual disabilities

Background: Sleep–wake problems and depressive symptoms are common in people with intellectual disabilities (IDs) and are thought to be related to the unstable sleep–wake rhythm in this population. Previously, we showed that after increasing environmental light exposure, mid-sleep and sleep onset advanced, and mood improved over a period of 14 weeks after installing environmental dynamic light installations in the living room of people with IDs. We invited participants of that short-term study to take part in the current study on sleep–wake rhythm, mood and behaviour in older adults with IDs 1 year after installing environmental dynamic light installations in the common living rooms of six group homes. Methods: A pre–post study was performed from October 2017 to February 2019. We included 45 participants (63.5 ± 8.5 years, 67% female) from six group home facilities who provided data at baseline (9, 4 and 1 weeks prior to installing light installations), short term (3, 7 and 14 weeks after installing light installations) and 1 year (54 weeks after installing light installations). Wrist activity was measured with actigraphy (GENEActiv) to derive the primary outcome of interdaily stability of sleep–wake rhythms as well as sleep estimates. Mood was measured with the Anxiety, Depression and Mood Scale. Behaviour was measured with the Aberrant Behaviour Checklist. Results: One year after installing dynamic lighting, we did not find a change in interdaily stability. Total sleep time decreased (β = −25.40 min; confidence interval: −10.99, −39.82), and sleep onset time was delayed (β = 25.63 min; confidence interval: 11.18, 40.08). No effect on mood or behaviour was found. Conclusions: We did not find a change in sleep–wake rhythm, mood or behaviour in older persons with IDs living in care facilities 1 year after installing the light. We did find evidence for a long-term effect on sleep duration and sleep timing. The results have to be interpreted with care as the current study had a limited number of participants. The need for more research on the long-term effects of enhancing environmental light in ID settings is evident.