Sleeping with the television switched on may affect more than sleep quality, with research linking exposure to light at night to changes in heart health and the body's internal clock. Studies suggest that artificial light during sleeping hours can interfere with circadian rhythms, the natural processes that regulate sleep and other bodily functions. Researchers have increasingly examined whether repeated exposure to light at night is associated with a higher risk of cardiovascular problems.

A study published in JAMA Network Open in October 2025 analysed data from 88,905 adults aged over 40 who wore light sensors for one week. Researchers tracked their health outcomes over approximately nine and a half years to investigate the relationship between nighttime light exposure and cardiovascular disease. The findings showed that people exposed to the brightest nighttime conditions had higher rates of several cardiovascular conditions than those who experienced darker nights. These included coronary artery disease, heart attacks, heart failure, atrial fibrillation and stroke.

The study found that participants in the highest nighttime light exposure group had a 56 per cent higher relative risk of heart failure and a 47 per cent higher relative risk of heart attack compared with those in the lowest exposure group. The researchers accounted for several established cardiovascular risk factors, including smoking, physical activity, diet and sleep duration. However, the findings demonstrate an association rather than proving that nighttime light directly causes these conditions.

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Other research has examined the relationship between sleeping with a television on and overall sleep health. An analysis of 47,765 women participating in the Sister Study found that sleeping with a television on was associated with a higher prevalence of short sleep, insomnia symptoms and inconsistent sleeping patterns. The researchers suggested that exposure to indoor light at night could contribute to poorer sleep, although the observational findings cannot establish a direct cause-and-effect relationship.

Scientists believe that light exposure during normal sleeping hours may disrupt the body's circadian rhythm and interfere with the biological signals that regulate rest. Sleep disruption can also affect processes involved in cardiovascular and metabolic health. The extent of these effects may depend on factors such as the intensity and duration of light exposure, individual sleep patterns and other health conditions.

Reducing unnecessary light in the bedroom may help support better sleep. Switching off the television before going to bed, keeping bedroom lighting low and maintaining a consistent sleep schedule are practical ways to create a darker sleeping environment. While current research does not establish that sleeping with a television on will inevitably cause heart disease, the findings support limiting avoidable nighttime light exposure as part of healthy sleep habits.

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