"Dear Dr Macfarlane, 

My husband has difficulty sleeping at night, which is making him quite agitated. Our doctor mentioned this could be due to a change in his circadian rhythms. Could you please explain what circadian rhythms are and how they can impact a person's behaviour?

Thanks, Carol" 

“What are circadian rhythms?”

Thanks for your great question. Circadian rhythm refers to the natural internal process that regulates an individual’s sleep-wake cycle – often referred to as a person’s body-clock.  

Light plays an important role in maintaining a person’s circadian rhythm as it triggers various responses in the human body that are important for sleep. After food, light is the most important input in controlling bodily function. 

People living with dementia often experience disrupted sleep patterns, which can significantly affect their mood and overall health. The amount of natural light a person is exposed to can greatly influence their sleeping patterns. Increasing exposure to natural light, such as through a window or by taking a morning walk can help set a person’s circadian rhythm and aid sleep.  

Similar to prescribing medication, around 30 minutes of exposure to natural light is recommended. It’s also important to ensure darkness at night to promote restful sleep.  

In care homes, there may be a lack of natural light during the day and excessive exposure to artificial light during normal sleeping hours. And it’s important that the care environment is adapted to support exposure to a regular 24-hour cycle of light and dark – setting a person's circadian rhythm. Merely being exposed to interior lighting levels without natural light is insufficient. 

More information about the role of light and practical solutions to ensure a person is receiving adequate light exposure, can be found in the publication Enlighten.