Getting a good night’s sleep is one of the most important parts of staying healthy.
Good sleep helps the brain store memories, supports the immune system, repairs the body, improves mood, and gives people the energy they need for daily life.
When people do not sleep well, they may struggle to concentrate, feel tired during the day, and face a higher risk of health problems such as obesity, diabetes, heart disease, depression, and memory decline.
While many people focus on bedtime routines, a new study suggests that what happens during the day may be just as important.
Researchers led by scientists at the University of Manchester have discovered that spending more time in bright, steady daylight may help people fall asleep earlier, sleep more deeply, and enjoy better-quality rest.
Their findings, published in the journal npj Biological Timing and Sleep, add to growing evidence that light plays a major role in controlling the body’s natural sleep-wake cycle.
Inside the brain is an internal body clock, often called the circadian rhythm. This clock helps decide when people feel awake and when they become sleepy. Light is the strongest signal that keeps this clock working properly. Natural sunlight tells the brain that it is daytime, while darkness signals that it is time to prepare for sleep.
Modern lifestyles, however, have changed this natural pattern. Many people spend most of the day indoors under relatively dim lighting and then spend their evenings surrounded by bright lights from homes, televisions, computers, and mobile phones. Scientists believe this mismatch may confuse the body’s internal clock and contribute to poor sleep.
Although laboratory experiments have shown that light affects sleep timing, the researchers wanted to know whether the same thing happens during normal daily life. To answer this question, they studied 89 adults as they went about their everyday routines.
Each participant wore a small light sensor that measured melanopic light. This is the type of light that has the greatest influence on the body’s internal clock. They also wore a consumer sleep tracker that recorded when they slept and how much time they spent in different stages of sleep. In addition, participants completed daily sleep diaries describing their own sleep experience.
Together, these devices collected more than 500 days of real-world information. After analyzing the data, the researchers found several clear patterns.
People who spent more time in brighter daytime light usually fell asleep earlier at night and woke up earlier in the morning. Those whose daily light exposure stayed more consistent from one day to the next also had healthier sleep schedules.
Another important finding involved deep sleep. Deep sleep is one of the most important stages of sleep because it helps the brain process memories, allows the body to recover, and supports overall health.
The researchers found that people with more stable light exposure and fewer sudden changes between dim and bright light experienced stronger deep sleep during the first part of the night.
The team also compared information from the wearable devices with participants’ own reports about how well they slept. In general, the two matched closely. However, when sleep became more disturbed, especially when deep sleep or rapid eye movement (REM) sleep was reduced, people became less accurate at judging the quality of their own sleep.
Lead author Altug Didikoglu, from the University of Manchester and the Izmir Institute of Technology, said the findings suggest that brighter days and more consistent light exposure may be a simple way to improve sleep. He also noted that affordable wearable devices make it possible to study sleep and light exposure in everyday life instead of only in laboratories.
Overall, this study provides strong real-world evidence that healthy light habits may be an important part of healthy sleep. While the research cannot prove that daylight alone causes better sleep, the large amount of everyday data strengthens the findings.
Future studies involving larger groups of people and longer follow-up periods will help confirm these results. In the meantime, spending more time outdoors during daylight hours and maintaining a regular daily routine may be simple steps that help many people enjoy better sleep and better overall health.
The study was led by researchers from the University of Manchester and was published in npj Biological Timing and Sleep.
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