Almost every major disease in the developed world - Alzheimer's, cancer, obesity and diabetes- shows a causal link to lack of sleep. Sleep disruption degrades mental health, reduces work-place productivity and increases absenteeism, and increases the burden on health and social care systems. Homes that remain comfortable at night enable quality sleep which enhance health and well-being and supports continued independent living.

Sleep is eroded by numerous personal factors such a stress and ill-health, but environmental factors are also important, especially bedroom temperatures. In a recent national survey over 4.5 million English households reported bedrooms that were often or always uncomfortably warm. Dwellings in London and the SE of England were most affected with flats, small dwellings and modern buildings particularly at risk. Socially disadvantaged households were disproportionately affected.

As the climate warms, the frequency, intensity and duration of heatwaves is increasing. As cities become denser, the urban heat island intensifies, and noise levels rise. In the 2003 European heat wave, there may have been over 70,000 premature deaths in 16 countries across Europe.

There are concerns that rising temperatures will initiate the uptake of air-conditioning (AC) in dwellings, which will place additional loads on the electricity supply networks and, as AC is costly to buy and run, will accentuate the societal inequalities.

Bedroom adaptations and behavioural change can improve the indoor environment. Public Health England's recommendations on staying cool in the summer are generic, and their applicability for many households in unknown. Whilst effort is being directed to reducing night-time overheating in new dwellings, there is no guidance, and no regulation, to protect existing dwellings from overheating.

This project brings together a multi-disciplinary team of sleep scientists, engineers and experts in user centred design and health. They will work with social housing providers, local authorities, housing developers and government departments. Healthy adults of all ages living in flats in London will be actively involved in the study.

Sleep quality measurement, sleep diaries, questionnaires, environmental monitoring, dwelling surveys and thermal modelling will seek to answer three questions:
1. What environmental factors (night-time temperatures, noise levels and air quality) lead to degradation of sleep quality in different people? Currently, for example, there is no credible UK night-time overheating criterion.
2. How might people achieve better quality sleep? Simple behavioural changes before and during sleep, or bedroom adaptations, like shading and improved ventilation, can improve summertime comfort, but by how much and for which people living in which sort of flats?
3. How might existing homes be refurbished to both reduce energy demand and improve summertime comfort?

The work involves people living in flats in London, who will help refine the research programme and enable monitoring of their bedrooms and sleep quality, and the way they control temperatures during heat waves. They will be the first beneficiaries of the research.

The work is important to builders, engineers and architects who lack a robust method for predicting overheating risk, and to social housing providers who want to objectively target properties that provide unacceptable summertime conditions. The research will also: provide social and healthcare professionals with better advice about how people can improve summer night-time comfort; enable social housing providers to plan and prioritise refurbishment, and inform future building regulations concerned with maintaining comfort, without air-conditioning, in existing buildings.

Most importantly, the work will protect the health and well-being of UK citizens as urbanisation continues and the climate warms.