Artificial light at night is more damaging to your health than you think: it not only increases the risk of cardiovascular diseases, but also disrupts sleep, metabolism and hormonal balance. However, the risk can be reduced with simple measures.
Street lights in front of the window, the glowing alarm clock on the bedside table or the smartphone display – artificial light at night has long since become the norm. But a new study shows that even small light sources in the bedroom can cause significant harm to our health.
Dramatic increase in light pollution
Nighttime illumination worldwide increased by almost 50 percent between 1992 and 2017, satellite images show. It rarely gets really dark, especially in big cities. The consequences for our health are more serious than previously thought.
An international research team led by Daniel Windred and Angus Burns conducted a large-scale study of 88,905 adults over the age of 40 to investigate how exposure to light at night affects the cardiovascular system. The results published in the journal “JAMA Network Open” are alarming.
Heart attack risk increases by over 50 percent
For the long-term study, the participants wore sensors on their wrists for a week that measured light exposure every 30 minutes. The researchers created individual 24-hour light profiles from over 13 million hours collected. They then provided medical support to the test subjects for almost ten years.
The results are clear: People exposed to strong light at night had a 45 to 56 percent higher risk of heart attacks and heart failure. The risk of stroke and coronary heart disease also increased by 28 to 30 percent.
Particularly noteworthy: These connections remained even after the researchers took known risk factors such as smoking, alcohol consumption, diet and sleep duration into account.
Why light is so dangerous at night
Over hundreds of millions of years, evolution has shaped our internal time system, which is based on the natural light-dark cycles. This approximately 24-hour biological rhythm controls vital body functions:
- Sleep-wake rhythm
- metabolism
- Hormone production
- Body temperature
Artificial light disrupts this finely tuned system. Jonathan Cedernaes from Uppsala University explains: “Today, irregular sleep-wake times are very common. Up to two thirds of adults shift their rhythm from weekdays to days off by two hours – a ‘social jet lag’ that compounds the effects.”
The consequences are diverse:
- Impaired melatonin secretion
- Increased heart rate
- High blood pressure
- Poorer deep sleep
- Worsened insulin sensitivity
Simple measures for healthy sleep
The good news: The risk can be significantly reduced using simple measures. These measures help to optimally darken the bedroom:
Can be implemented immediately:
- Turn off your smartphone and television at least an hour before going to bed
- Replace digital alarm clocks with analogue models or dim the display
- Tape off standby lights on electrical appliances
- Use a sleep mask
Long-term solutions:
- Install blackout curtains or shutters
- If there is street lighting in front of the window: check additional darkening
- LED night lights with warm, dimmed light for nighttime orientation
Sustainable health starts in the bedroom
The study shows once again how important it is to respect natural rhythms. A darkened bedroom is not only good for your health, but also sustainable: less artificial lighting means less energy consumption and reduced light pollution.
Limitation of the study: The participants were predominantly white and had higher levels of education and income. It is not yet clear whether different light colors have different effects. Nevertheless, the message is clear: darkness at night is essential for our health.
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