Shelley Betz, an executive assistant in Atlanta, can't sleep without her box fan whirring on full speed next to her bed. She relies on the fan's noise to drown out all other sounds and lull her into a deep slumber, a tactic that has proven so effective she put box fans in her children's rooms beginning in infancy.
"The minute they heard that humming sound come on, it helped to put them to sleep a lot easier," she says in an email. "The little things that would wake other people's children up at night, mine never heard. The only bad drawback is they sort of need it to sleep. The nights they don't have one they struggle."
Betz is hardly alone in her love of the nighttime box fan. Chances are, you know at least a few people who rely on the small appliance for a good night's rest. (You might be one of them yourself.) And, if you look closely the next time you're checking into a hotel or waiting to board a cruise, you may spy travelers toting their own.
"People who sleep with a fan are capitalizing on what we call white noise. Just like white light, which encompasses all the colors on the spectrum, white noise encompasses all sound frequencies within typical human hearing," explains Kelsey Allan, a sleep expert with mattress manufacturer Sleep Train in an email interview. "Technically, true white noise is generated only electronically, but ambient noises like fans, distant cicadas, or gentle rain can produce a similar effect."
So, what's going on in the brains of folks who need fans that makes them different from others? The answer likely lies in how our brains are wired, according to research. Sleep spindles, in particular, seem to be the culprit. These can be seen on electroencephalogram (EEG) tests, and present as short brain wave bursts that increase and decrease, causing a spike (or spindle) to form on the EEG reading.
Research indicates that people who experience sleep spindles more often have a better defense against outside noise than those who don't experience frequent sleep spindles. It doesn't change from night to night, either – a person's sleep spindle production is likely to be static across time.
How do the sleep spindles accomplish this enviable feat of blocking noise? Scientists think that, since they're produced in the portion of the brain called the thalamus (the area that all sound and sensory information must visit before being farmed out), they actually run into the sounds and block them from waking a person up. Since sleep spindles are more common during REM sleep, they're most successful at completing this task during such phases.
Another study, published in the journal PNAS used optogenetics (control of both light and genetics) to influence sleep spindle production in mice. The scientists found that an increase in sleep spindles was correlated with an increase in NREM sleep (deep sleep). Thus, they concluded that effective modulation of the sleep spindles could actually hold the key for curing patients with sleep issues, although that concept requires further research.
No one knows for sure why some people have rock star sleep spindles while others suffer through the curse of light sleeping. But it is often the change in sound rather than the sound itself that wakes up the brain.
Although you can get a "white noise" effect from a sound machine or even AM radio static, the fan has the extra advantage of cooling you down, notes Kevin Gaffney, M.D., neurologist and sleep medical director at Mischer Neuroscience Center at Memorial Hermann The Woodlands Medical Center. "Your normal body temperature of 97.8 degrees [36.5 Celsius] (not 98.6) drops by 1-2 degrees at night. If you have to struggle to lower your body temperature, this can decrease your sleep quality, " he says.