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Sleeping with lights on (whether the television is on, the cell phone screen or a lamp) may seem normal or even routine, but Science guarantees that this routine can harm sleep and affect several dimensions of health.
The human body works according to a cycle of approximately 24 hours, known as the circadian rhythm, which helps regulate periods of wakefulness and rest. Light is one of the main factors that synchronize this internal clock, therefore, light exposure in the hours before sleep, or during the night, can disorganize this natural mechanism.
At the center of this system is the so-called suprachiasmatic nucleusa brain structure located in the hypothalamus, responsible for coordinating the organism’s biological rhythms. When light enters the eyes, the retina converts it into electrical signals that are sent directly to that region of the brain. Even with your eyes closed, some light can pass through the eyelids and reach the retina, keeping the brain sensitive to the light environment.
One of the most important consequences of this exposure is the suppression of melatonin, an essential hormone to prepare the body for sleep. When its production is inhibited, sleep tends to become more superficial, irregular or insufficient. And the effects are not limited to rest, explains . Circadian rhythms also influence the immune system, digestion, metabolism and the production of other hormones, such as cortisol. In short, disrupting the body clock can have broader implications than just waking up tired.
The studies cited in the text also point to an association between night light and a greater risk of health problems, including mood disorders and cardiovascular issues. Among the different types of light, blue light — emitted by televisions, smartphones and tablets — is considered especially problematic. This wavelength increases alertness, just when the body should be preparing to rest.
Some doctors therefore recommend avoid screens up to three hours before bed. While there is research that suggests blue light can affect vision and contribute to retinal damage or cataract formation, there is not yet enough data to conclude that habitual exposure from digital devices reaches toxic levels.
Still, sleeping well is still more important than keeping a screen on at night. For those who have difficulty falling asleep without television, an intermediate solution may involve use automatic timersin addition to resorting to blackout curtains or sleep masksespecially in areas with high light pollution.
