Europe is undergoing a demographic change with a rapidly growing population of 65 years+. This challenges municipalities and hospitals as the ageing citizens need care and treatment due to an age-related decline in physical and mental capacity. Therefore municipalities are experiencing a growing need for sufficient and customized housing, which can support the elderly citizens in sustaining well-being and health along with preventing functional decline. Well-fare technologies, such as Circadian adjusted LED-based lighting (CALED), are suggested as a remedy for this.

To obtain proper visual sharpness and better contrast, people of older age require heightened light levels due to age-related failing vision. Furthermore, inappropriate light at night disrupts not only sleep but also the timing of the circadian rhythm, with negative consequences on cognition and emotions. Therefore CALED is being increasingly considered for use in hospitals and elderly housing because of its wide spectrum of wavelengths, good contrast and fast switching, and possibility to support a normalised circadian rhythm.

Lighting based on LED has been shown to improve the quality of sleep and to improve well-being in the elderly. However, it is not known whether CALED mimicking a normal circadian rhythm has the same benefits for elderly persons with frailty or dementia. The investigators therefore want to test the effects of CALED in elderly people with frailty and mobility disabilities and/or dementia living in elderly housing. The investigators hypothesise that CALED can improve sleep and well-being in both elderly with frailty and dementia.

Due to the technical requirements, CALED will not be installed in all elderly housing facilities at Sundhedshuset, Albertslund, Denmark, limiting the number of participants receiving the intervention to 24. CALED will be installed in the residents rooms/flats and in the common areas. Residents accepting participation will comprise the following (numbers are the maximal possible): 15 elderly with frailty receiving CALED as an intervention, 9 people with dementia receiving CALED as an intervention, and 15 elderly with frailty not receiving CALED during the trial as a control group (Group 3).

The elderly receiving CALED as an intervention (15 people with frailty, 9 people with dementia) will be randomized to two groups (Group 1 and Group 2) based on equal distributions of elderly with dementia and frailty in each group and similar numbers of men and women in each group. Since the residents spend a lot of time in the same common areas where CALED is installed, the two groups are subjected to the intervention at the same time, and Group 2 therefore has a delayed start. Group 1 starts with an 8 week control period followed immediately by an 8 week intervention period. Group 2 starts with an 8 week intervention period, at the same time as Group 1, followed by and 8 week control period. Group 3 has a 16 week control period starting 4 weeks after the beginning of the control period for Group 1, and ending 4 weeks before the end of the control period for Group 2.

Timeline: Participants are included when informed consent has been obtained. CALED is installed afterwards. Randomization takes place immediately before baseline testing of Group 1, and participants are randomized by block randomization. The trial participants will be assessed at baseline, in the 4th, 8th, 12th, and 16th week, respectively. For Group 1, baseline testing takes place within two weeks prior to the beginning of the Control period. For Group 2 baseline testing takes place within two weeks prior to the beginning of the Intervention period. For Group 3 baseline testing takes place within the two weeks prior to the beginning of the Control period. See outcome measures for further details of tests.

Data collection: All data collection and assessments will be performed at "Sundhedshuset" by trained staff under the instruction and supervision of the primary investigator. Date of all assessments will be noted. Blood samples (approximately 20 ml) will be taken in "Sundhedshuset" by trained staff under the supervision of the primary investigator. Date and time of blood sampling will be documented. Blood samples will be transported to Hvidovre Hospital after collection, and plasma and serum will be stored in a biobank at -80°C until analysis.

Data management: All case report forms will be checked for errors and missing data by the assessor before being archived in a trial database and all paper-based versions will be locked in a filing cabinet in a locked room to ensure confidentiality. Data management will follow the rules of the Danish Data Protection Agency.

Power calculation: A power calculation for the Pittsburgh Sleep Quality Index (PSQI) based on a paired t-test with an alpha of 0.05, 24 pairs, a correlation of 0.8, and a standard deviation of 5.6 showed it possible to detect a minimal clinical difference of 2 with a power of 0.76. This does not account for possible drop-outs, but we expect that the inclusion of 15 control participants not exposed to CALED will increase power. Moreover, we expect that a maximum of 3 citizens will not want to participate.

We have included plasma levels of soluble urokinase plasminogen activator receptor (suPAR) as an objective and stable marker of general health status as another primary end-point. A power calculation for suPAR based on a two-sided paired t-test with an alpha of 0.05, a power of 0.8, a standard deviation of 0.5 ng/mL, and a clinical significant difference of 0.3 ng/mL (effect of healthy versus unhealthy diet is 0.35-0.55 ng/mL) gave a study population of 24 subjects. This does not account for possible drop-outs, but we expect that inclusion of 15 control participants not exposed to CALED will increase power.

Descriptive data and outcome analysis: Data will be presented as means with standard deviations, medians with inter-quartile ranges or frequencies with percentages depending on the distribution of the variable.

The primary analysis for the primary outcomes will be performed using the SAS procedure PROC MIXED (dif (intervention-control)).The difference in the PSQI scores and suPAR levels between the intervention period and the control period will be analysed using mixed models, with treatment (intervention and control) and period (period 1 and period 2) as fixed effects and the participant identification as random effect. Secondly, the models will be adjusted for baseline PSQI scores and suPAR levels, respectively. The primary analysis will follow the intention-to-treat principle using multiple imputations in case of missing outcome measures. For the secondary outcomes, similar analyses will be performed. All models will be investigated for goodness-of-fit (linearity, variance homogeneity and normal distribution of residuals) by visual inspection of plots and remodelling will be performed accordingly. All statistical tests will be performed using SAS (SAS Institute Inc., Cary, NC, USA) and p values ≤0.05 will be considered statistically significant.

Inclusion Criteria:

• Group 1 and 2: Frail elderly (+65 years) and elderly (+50 years) with dementia, who live in the flats/rooms in Sundhedshuset, Albertslund, Denmark that have been chosen for a test installation of CALED will be invited to participate.
• Group 3: Frail elderly (+65 years) who live in the flats/rooms in Sundhedshuset, Albertslund, Denmark that have not been chosen for a test installation of CALED will be invited to participate.

Exclusion Criteria for Group 1, 2, 3:

• Terminal illness