The common habit of keeping a smartphone close by during sleep, often placed directly under the pillow, raises several safety and health concerns.
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This practice is strongly discouraged, as its risks stem from a combination of physical hazards, energy-related exposures, and behavioral disruptions.
Such extreme proximity creates conditions that can negatively impact both the bedroom environment and the body's biological processes. Examining these various aspects reveals why safety experts and sleep specialists strongly warn against this behavior, according to a report by "Biology Insights"—a platform specializing in simplified scientific and medical content—reviewed by Al Arabiya Business.
Placing a phone under a pillow or any bedding poses a significant thermal risk, as the device generates heat while operating.
Modern smartphones rely on lithium-ion batteries, which can overheat—especially when under heavy usage or while charging.
Soft materials, such as pillows or blankets, trap this heat and prevent it from naturally dissipating into the air. This lack of ventilation leads to a rapid temperature rise within the phone's structure and battery. Such localized heat can swiftly cause component damage or battery failure, and in severe cases, trigger thermal runaway.
When a lithium-ion battery enters thermal runaway, it can ignite nearby flammable materials, posing a serious fire hazard. Fire officials have documented instances where phones left charging under pillows ignited bedding and caused residential fires.
To mitigate this risk, phones should only be charged on hard, exposed, non-flammable surfaces that allow adequate airflow around the device.
Cell phones operate by transmitting and receiving radiofrequency (RF) energy, which is a form of non-ionizing electromagnetic radiation.
This energy is regulated based on its ability to cause tissue heating, measured by a metric known as the Specific Absorption Rate (SAR). Regulatory bodies, such as the U.S. Federal Communications Commission (FCC), require all phones to operate within established SAR limits to ensure safety during normal use.
Although the emitted energy is low, exposure intensity is governed by a physical principle known as the inverse-square law. This principle states that the amount of absorbed energy decreases rapidly as the distance from the radiation source increases. Consequently, placing a phone directly next to the head, such as under a pillow, increases nearby tissue exposure to RF energy.
The International Agency for Research on Cancer (IARC) has classified radiofrequency electromagnetic fields as "possibly carcinogenic to humans," based on limited evidence.
However, current research does not establish a direct link between cell phone use and an increased risk of cancer. Nonetheless, increasing unnecessary exposure by keeping the phone right next to one's head runs counter to basic physical principles that advocate for minimizing absorbed energy.
Disruption of sleep quality is one of the most prominent consequences of sleeping near a phone. Smartphones and tablets emit blue light, which the body's circadian system interprets as daylight. Exposure to this light suppresses the production of melatonin, the hormone responsible for signaling to the brain that it is time to sleep.
Even checking a phone briefly can delay melatonin secretion, thereby shifting the body's natural circadian rhythm.
This biological interference makes falling asleep more difficult and reduces the duration of deep, restorative sleep. The resulting sleep deprivation negatively impacts cognitive performance the following day and overall mood.
Furthermore, the mere presence of an active device nearby keeps the brain in a state of alertness due to mental and psychological stimulation. Notifications, sounds, and vibrations cause frequent sleep interruptions and fragmentation.
Similarly, browsing content before bed—such as checking social media—activates the brain's reward pathways, making the transition to a restful state required for sleep much harder.
This psychological anxiety, driven by the feeling of needing to remain perpetually available, maintains a high level of vigilance, which hinders reaching deep, restorative sleep.
Al Arabiya
