Many people like to sleep with some light on, such as from a nightlight or the glow of a TV or phone screen. However, a recent study has shown that sleeping with bright light on can have negative effects on our health.

The Study

The study, conducted by researchers from the University of Haifa in Israel and published in the journal Chronobiology International, involved 20 healthy adults who spent five nights in a sleep laboratory.

During the first three nights, the participants slept in complete darkness. On the fourth night, they slept with a dim light on. On the fifth night, they slept with a bright light on, equivalent to the brightness of a cell phone screen or TV.

The researchers measured various physiological and psychological metrics, including heart rate, cortisol levels, subjective mood, and sleep quality.

They found that sleeping with the bright light on led to several negative impacts on the participants’ health.

Health Risks of Sleeping with Bright Light On

Disrupts Sleep Quality

Perhaps the most obvious health risk of sleeping with bright light on is that it can disrupt our sleep quality.

The researchers found that when participants slept with the bright light on, they had more fragmented sleep, waking up more times during the night and spending less time in deep sleep. This can leave us feeling tired and groggy throughout the day, and over time can lead to chronic sleep deprivation.

Increases Cortisol Levels

Cortisol is a hormone that is naturally released by our bodies in response to stress. However, high levels of cortisol can have negative effects on our health, including weight gain, mood disorders, and a weakened immune system.

The researchers found that when participants slept with the bright light on, their cortisol levels were higher than when they slept in complete darkness. This suggests that sleeping with bright light on can increase our stress levels and make it harder for us to relax and fall asleep.

Impairs Cognitive Function

Getting a good night’s sleep is essential for cognitive function, including memory, attention, and decision-making.

However, the researchers found that when participants slept with the bright light on, they performed worse on cognitive tasks the following day than when they slept in complete darkness. This suggests that sleeping with bright light on can impair our ability to think and make decisions, which can have negative impacts on our work, school, and personal lives.

Increases Risk of Depression

Poor sleep quality and disrupted circadian rhythms have been linked to an increased risk of depression.

The researchers found that when participants slept with the bright light on, they had lower subjective mood ratings the following day than when they slept in complete darkness. This suggests that sleeping with bright light on can have negative impacts on our emotional well-being and increase our risk of developing depression.

Recommendations

Based on these findings, it is recommended that we sleep in complete darkness in order to promote optimal health and well-being.

This means turning off all lights, covering any electronic displays or LED lights, and using blackout curtains or an eye mask if necessary. It is also recommended to avoid using electronic devices such as phones, tablets, or TVs before bedtime, as the blue light emitted from these devices can disrupt our circadian rhythms and make it harder for us to fall asleep.

Conclusion

In conclusion, sleeping with bright light on can have negative impacts on our health, including disrupted sleep quality, increased cortisol levels, impaired cognitive function, and an increased risk of depression.

To promote optimal health and well-being, it is recommended that we sleep in complete darkness and avoid using electronic devices before bedtime.