Summary: A large-scale, long-term study finds that modest changes to the indoor environment—cooler bedrooms at night and brighter indoor light during the day—can meaningfully improve sleep for people living with dementia. Researchers analysed more than 26,000 days of data collected by contactless, zero-burden sensors installed in participants’ homes.
The analysis linked hotter-than-usual nights with more fragmented sleep and higher breathing rates, while brighter-than-usual daytime indoor light was associated with longer, less disrupted sleep and lower respiratory rates. The results suggest that simple, practical adjustments to temperature and light may improve sleep, reduce symptom burden and help people with dementia remain independent for longer.
Key Findings
- Hot nights disrupt sleep: Nights with elevated bedroom temperatures were associated with more disrupted sleep and increased respiratory rate.
- Daylight and bright indoor light improve sleep: Days with higher indoor light levels correlated with longer sleep, fewer awakenings and reduced breathing rate during sleep.
- Small, practical changes can help: Adjusting bedroom temperature at night and increasing daytime indoor light exposure may lessen sleep disturbance and support daily functioning.
Source: University of Surrey
Study overview
Led by the University of Surrey and published in the journal Sleep, the study examined 26,523 days and nights of environmental and physiological data from 70 people living with dementia in their own homes. Data were gathered using zero-burden technologies—under-mattress bed sensors, contactless bed-occupancy monitors and environmental sensors that continuously measured indoor light and temperature without requiring participants to wear or charge devices.
Researchers compared indoor conditions to sleep timing, duration, fragmentation, heart rate and breathing rate across seasons and day-to-day variations. They found that seasonal shifts in outdoor light and temperature were reflected indoors and corresponded with changes in sleep timing and physiology. Importantly, even after accounting for seasonal effects, night-to-night increases in bedroom temperature and reductions in daytime indoor light were independently associated with poorer sleep.
Sleep disturbances are common in dementia—frequent nighttime awakenings, long daytime naps and an unstable circadian rhythm can worsen daytime functioning and memory. By showing that modifiable indoor conditions relate to objective measures of sleep and physiology, the study highlights low-cost, non-pharmacological strategies to improve quality of life for people with dementia.
Research methods and collaboration
The research team worked in collaboration with Imperial College London and Surrey and Borders Partnership NHS Foundation Trust, and was funded by the UK Dementia Research Institute through the Care Research & Technology Centre. The project used long-term, continuous monitoring with sensors placed under mattresses and around the home to build a detailed, real-world picture of how the indoor environment affects sleep and physiology.
Because the technologies used are zero-burden, they collected reliable data across seasons and years without adding effort or inconvenience for participants. This longitudinal approach allowed the researchers to detect patterns that short-term studies or caregiver reports might miss.
Practical implications
The study found that some homes stayed consistently warm year-round, which suggests straightforward interventions—such as lowering bedroom thermostats overnight—could improve sleep and potentially reduce energy costs. Conversely, increasing exposure to brighter indoor light during the day appears beneficial for sleep consolidation. The effects varied between individuals, indicating that some people with dementia are more sensitive to temperature and light changes than others.
With climate change increasing the frequency of hot nights, keeping bedrooms cooler and maintaining good daytime lighting may become even more important for this vulnerable population, who typically spend most of their time indoors.
Expert commentary
Professor Anne Skeldon, Head of the School of Mathematics at the University of Surrey and co-author of the study, emphasised the value of long-term data: “Analysing millions of hours of data allowed us to see how indoor temperature and light patterns affect sleep in real homes. Our approach captures long-term trends that short studies or carer reports cannot.”
Professor Derk-Jan Dijk, Director of the Surrey Sleep Research Centre and co-author, added: “Longitudinal monitoring of the indoor environment alongside sleep and physiology shows the importance of indoor conditions for health. Zero-burden digital technologies offer a promising way to monitor and potentially prevent ill health in the community.”
About this Alzheimer’s disease research news
Author: Anne Skeldon
Source: University of Surrey
Contact: Anne Skeldon – University of Surrey
Image: The image is credited to Neuroscience News
Original Research: Closed access. “Seasonal and daily variation in indoor light and temperature are associated with sleep disturbance in dementia” by Anne Skeldon et al. SLEEP
Abstract
Seasonal and daily variation in indoor light and temperature are associated with sleep disturbance in dementia
Human sleep and physiology evolved to respond to daily and seasonal environmental rhythms driven by the Earth’s rotation and the Sun. How those mechanisms operate in people who are mostly exposed to indoor environments, such as those living with dementia, has been unclear.
We analysed 26,523 days of combined outdoor and indoor environmental sensor data and contactless behaviour-and-physiology sensor data tracking bed occupancy, heart rate and breathing rate from 70 people living with dementia. Indoor light and temperature, sleep timing, duration and fragmentation, and the timing of the heart rate minimum all varied by season.
Beyond seasonal trends, higher bedroom temperatures and lower daytime indoor light were independently associated with more disrupted sleep and higher respiratory rate. These findings indicate that controlling indoor light and temperature may be an effective, practical approach to improving sleep and physiological health in people living with dementia.