Background <p>Bright Light Therapy is effective in improving sleep and circadian rhythms. However, little is known regarding the effects of BioDynamic Lighting. The current study examined whether BioDynamic Lighting is effective for improving sleep and rest-activity rhythms in nursing home residents with dementia, and compared its effects with those of Bright Light Therapy and standard light.</p> Methods <p>Forty-two residents with dementia were included in this nonrandomized 12-month crossover trial. Residents were exposed to BioDynamic Lighting, Bright Light Therapy, and standard light (twice), each for 3-months. The sleep parameters were measured via wrist-actigraphy and bed sensors.</p> Results <p>Multilevel regression analyses revealed no significant changes in the 24-h rest-activity and sleep variables intradaily variability, interdaily stability, amplitude, sleep efficiency, sleep onset latency, number of awakenings, duration of nocturnal awakenings, total sleep duration or night-time bed exits after 3 months of BioDynamic Lighting or Bright Light Therapy exposure compared to baseline. After BioDynamic Lighting discontinuation, we observed a significant increase in the number of nocturnal awakenings (<i>d</i>=0.35, <i>p</i>=.01), and a decrease in sleep onset latency (<i>d</i>=-0.47, <i>p</i>=.003). No significant differences were observed in the effects of BioDynamic Lighting and Bright Light Therapy.</p> Conclusions <p>Neither 3-month BioDynamic Lighting nor Bright Light Therapy had significant effects on night-time sleep, 24-h rest-activity rhythm (actigraphy), or bed exits during the night (bed sensors). Elements that may have influenced our results include suboptimal sleep hygiene, such as long bed episodes, daytime napping and scheduled afternoon rest periods. Future studies in larger, adequately powered samples are needed to confirm these results.</p> Trial Registration <p>Dutch Trial Register (NTR7480, Registration Date: 1-10-2018).</p>