Arianna Huffington and I have at least one thing in common: We’re both obsessed with getting enough sleep. As a man who typically enjoys anywhere between 8 and 10 hours of shut-eye each night, even getting as little as six hours feels like some form of sleep-deprivation experiment, making me cranky, weird and lethargic. And that’s just scratching the surface. Here are a few of the other brutal side effects of missing out on essential Zs — and why they happen.
Besides tiredness, the most obvious result of not getting enough sleep is that aforementioned crankiness — the Mr. Hyde to your better rested Dr. Jekyll. “Complaints of irritability and [emotional] volatility following sleepless nights [are common],” observed a team of Israeli researchers in 2005, after putting those complaints to the test by following around a group of sleep-deprived medical residents.
The study found that the negative emotional effects of disruptive events — things like being interrupted while in the middle of doing something — were amplified by sleep loss. Why? “Sleep deprivation enhances a negative mood due to increased amygdala activity,” says Terry Cralle, a certified clinical sleep educator. The amygdala, he explains, is a brain structure closely tied to negative emotions such as anger and rage, and sleep loss can cause a disconnect between the amygdala and the area of the brain that regulates its functions. When that happens, you’re going to be in a seriously shitty mood.
A lack of sleep can impair your cognitive functions so badly that it’s like being too drunk to legally drive. According to research by Harvard’s Charles Czeisler, as reported by the National Geographic, “Going without sleep for 24 hours, or getting only five hours of sleep a night for a week, is the equivalent of a blood alcohol level of 0.1 percent,” which is the equivalent of consuming four or more drinks, depending on your weight.
“That’s because, when comparing the brain of someone who is sleep-deprived to the brain of someone who has slept normally, research shows reduced metabolism and blood flow in multiple brain regions,” Cralle says. “This prevents the brain from restoring its energy sources and therefore diminishes a person’s cognitive functioning.”
To put it another way, that part of the night where you’re drunk enough to sing karaoke is where you’re at mentally after a week of pretty lousy sleep.
Weakened Immune System
According to a 2009 study conducted at Carnegie Mellon University, people who sleep less than six hours a night are four times more likely to catch a cold than people who sleep for seven or more. There’s a significant body of research to show that immune function is tied closely to the body’s 24-hour circadian clock, and so, “When sleep is deprived, this cycle is weakened and disrupted, and the immune system suffers,” says Cralle.
A night — or even a week — of reduced sleep won’t turn you into Guy Pearce’s character from Memento. But studies have shown that long-term lack of sleep can damage your ability to form new memories and recall older ones. In 2014, a Harvard’s Nurses Health Study found that people who slept five hours or less every night were actually functioning at a memory level two years beyond their actual age — bad news for sleep-deprived older people.
A 2013 study, meanwhile, found that important brain waves are produced during sleep, which play a vital role in storing memories. “What we have discovered is a dysfunctional pathway that helps explain the relationship between brain deterioration, sleep disruption and memory loss as we get older,” wrote Matthew Walker, an associate professor of psychology and neuroscience at the University of California at Berkeley.
In short, the less sleep you get, the more Swiss cheese-like your brain becomes.
As if guys weren’t already in the midst of a sperm crisis, a Danish study from 2013, published in the American Journal of Epidemiology, found that men who experienced a lot of sleep disturbances have 29 percent less sperm in their semen than dudes who were able to get a solid eight hours in each night. Though researchers aren’t sure why lack of sleep equals lack of sperm, if you’re looking to have children in the near future, it’s worth keeping in mind.
Low Sex Drive
Of course, you may not even notice your depleted sperm, because sleep deprivation also can prevent you from getting horny in the first place. A 2011 study published in the Journal of the American Medical Association followed a group of 10 young men, who each slept five hours a night for one week. At the week’s end, researchers found that their subjects were unable to concentrate, had low energy and were resolutely unhorny.
Further, the male subjects displayed a 10- to 15-percent drop in testosterone levels over the course of this week, whereas most post-pubescent guys see their testosterone levels drop by just 1 or 3 percent every year. As the study’s co-author Eve Van Cauter explained to Science Daily, “Low sleep duration and poor sleep quality are increasingly recognized as endocrine disruptors.”
Translation: No sleep = no other fun stuff in bed, either.