Smartphones are often kept on nightstands or even under pillows, providing instant access to communication and entertainment until users fall asleep. This constant proximity raises questions about safety, particularly the potential long-term risks of keeping an active electronic device close to the body nightly. While the convenience is undeniable, concerns fall into three categories: energy exposure, sleep quality, and physical safety. Understanding these risks can help you decide whether your device should share your sleeping space.
Understanding Radiofrequency Energy
Cell phones communicate by emitting radiofrequency (RF) energy, a form of non-ionizing electromagnetic radiation. Unlike ionizing radiation (such as X-rays), RF energy is not strong enough to break chemical bonds. It can cause atoms to vibrate, generating heat only when exposure levels are very high, such as in a microwave oven.
All wireless devices sold in the United States must meet exposure limits set by the Federal Communications Commission (FCC), based on the Specific Absorption Rate (SAR). These limits prevent harm from excessive heat absorption. The World Health Organization (WHO) and the U.S. Food and Drug Administration (FDA) state that current scientific evidence does not link RF energy exposure within these limits to confirmed health problems.
The International Agency for Research on Cancer (IARC), a WHO agency, classified RF radiation as a “possible human carcinogen” (Group 2B). This means there is limited evidence of a link in humans and insufficient evidence in animals. Regulatory bodies maintain that exposure at or below current standards has not been established as a health risk. Since the power of RF energy drops sharply with distance, moving the phone a few feet away significantly reduces exposure while sleeping.
Disruption to Sleep Cycles
Beyond RF energy, a phone’s light and function pose a scientifically established problem for sleep quality. Smartphones emit high-energy blue light, which the brain interprets as a signal of daytime. Exposure to this blue light, particularly before bed, actively suppresses melatonin production. Melatonin is the hormone responsible for signaling the body that it is time to sleep.
The resulting drop in melatonin can delay sleep onset. Even after falling asleep, this disruption to the circadian rhythm can lead to lighter, more fragmented rest and reduced deep and REM sleep cycles. This often causes users to wake up feeling unrested despite adequate hours of sleep.
The psychological impact of having the device nearby also contributes to poor sleep hygiene, independent of light. The temptation to check notifications, scroll through social media, or read the news keeps the brain mentally aroused. Being “on call” conditions the mind to associate the bedroom with alertness rather than rest, negatively impacting the ability to transition into a restorative sleep state.
Physical Hazards from Heat and Charging
A more immediate danger of sleeping with a phone, especially while charging, involves physical hazards like overheating and fire. Smartphones contain lithium-ion batteries, which store a large amount of energy. When charging, the phone naturally generates heat that needs to dissipate into the surrounding air.
Placing a charging phone under a pillow, blanket, or mattress traps this heat, causing the battery temperature to rise rapidly. This lack of ventilation can lead to overheating, battery failure, and a significant risk of the device igniting, potentially reaching temperatures over 600°C. Since bedding materials are highly flammable, a fire can start and spread quickly while the occupant is asleep.
The risk of fire is also increased when using unbranded or damaged third-party chargers and cables. These accessories may not meet safety standards and can fail, leading to short circuits, excessive heat, or electrical fires. Safety experts caution against covering the device or placing it on any soft, flammable surface while connected to a power source.
Simple Adjustments for Safer Nighttime Use
To mitigate the risks associated with sleeping near your phone, adopt several practical adjustments.
Minimizing RF Exposure
To minimize RF energy exposure, keep the phone at least a few feet away from your head while sleeping, such as on a distant dresser. You can also significantly reduce energy emissions by switching the device to Airplane Mode before bed.
Protecting Sleep Quality
Stop using your phone for at least one hour before your intended bedtime. If you use the phone as an alarm, consider purchasing a dedicated, non-digital alarm clock to eliminate the need for the phone in the bedroom. Also, turn off all notifications and set your phone to “Do Not Disturb” mode to prevent mental arousal from late-night alerts.
Ensuring Physical Safety
Never charge your phone under your pillow, on your mattress, or under blankets. Always place the device and its charger on a hard, non-flammable surface, such as a wooden nightstand, with plenty of open air for ventilation. Only use certified, official charging accessories, and immediately discard any chargers that are damaged or appear to be overheating.