Exposure to light is an important factor in regulating sleep and sleep quality, especially for elderly people with a high risk of sleep problems. A systematic literature review was conducted to explore the current understanding of the relationship between light and sleep quality of the elderly, and to identify methodological gaps and soundness of existing studies to inform the design of future experimental studies. Specific focus is given to healthcare centres and similar settings due to their controlled environment and the high prevalence of sleep disturbances. Out of 406 publications screened from four databases—namely Google Scholar, Semantic Scholar, Lens.Org, and Scopus—380 studies remained after removing duplicates, and 19 studies published after 2002 that were relevant to the review topic were selected based on the PRISMA 2020 guidelines. The selected studies were analysed using six key aspects, which reflect typical components of experimental design such as participants’ characteristics, experiment and exposure duration, mode of light exposure, lighting and light interventions, experiment procedure, and data collection methods. The results indicated that many studies have limitations in terms of the accuracy and generalisability of findings in representing the entire elderly population due to issues with experimental design or control of the participants’ attendance. The results suggest that future studies should increase the duration of light intervention to around 21–35 days and the number of participants to around 14 and 47. The issues identified from the experimental designs of the selected studies provide valuable insights for establishing guidelines and recommendations for future studies.
Zhou et al. (2025) studied this question.