One would think they would know if they were sleep-deprived, or not. And one might not be inclined to think much beyond that.
Yet, signs of sleep deprivation may not always be this obvious (and there are other factors besides sleep loss that can make you feel fatigued). The late Nathaniel Kleitman, Ph.D., professor emeritus in physiology at the University of Chicago, came up with one of the simplest tests to determine if you're sleep deprived — and as a pioneer in sleep research, he was well qualified to know.
Not only did Kleitman co-discover REM sleep, but he published the first major textbook on sleep (“Sleep and Wakefulness” in 1939). He even stayed awake for 180 hours to figure out what sleep deprivation does to your body. Kleitman also spent more than one month underground in a cave — an environment without sunlight or schedules — in order to track changes in wakefulness and circadian rhythm. So when he suggested a way to test yourself for sleep deprivation, people took notice.
Sleep Deprived? Take the Sleep Onset Latency Test to Find Out
Kleitman's sleep onset latency test sounds complicated, but it's quite simple. And, “It's based on solid science,” said Dr. Michael Mosley, who is both a physician and a journalist for BBC in the U.K. Here's how it works: In the early afternoon, grab a spoon and head off to your darkened bedroom to take a nap. Place a metal tray on the floor beside your bed, and hold the spoon over the tray as you attempt to fall asleep.
Be sure to check the time as well. Next, when you inevitably fall asleep and the spoon crashes down onto the tray, waking you up, immediately check the time again and note how much time has passed.
If you fell asleep within five minutes, it means you're severely sleep deprived, according to Kleitman. If it took you 10 minutes to fall asleep, this is still a sign that you could use more sleep. If, however, you managed to stay awake for 15 minutes or more before falling asleep, you're probably well rested. If you don't happen to have a spoon and metal tray handy, you can still take this test by setting an alarm for 15 minutes to see if you fall asleep before it goes off, Dr. Mosley adds.
More Signs You're Sleep Deprived
In the video above, Health shares more signs that indicate you could use more shut eye, some of which may surprise you.
1.You Always Feel Hungry
Lack of sleep influences hormone levels, including increasing the “hunger hormone” ghrelin and decreasing leptin, which is involved in satiety. By activating your endocannabinoid system, which is involved in modulating appetite and food intake, sleep deprivation can even give you the munchies, similar to marijuana use.
2.You've Gained Weight
One of the consequences of eating more when you're sleep deprived is weight gain, although a lack of sleep also promotes metabolic dysfunction that further fuels weight gain. Losing as little as 30 minutes of sleep each night can disrupt your metabolism enough to cause weight gain. In fact, each half-hour of sleep debt incurred during weeknights raised one study's participants' risk for obesity and insulin resistance by 17 percent and 39 percent respectively after one year.
What this means is that if you need eight hours of sleep but consistently only get seven, you may theoretically raise your risk of obesity by about 34 percent and simultaneously jack up your chances of insulin resistance — which is a hallmark of most chronic diseases, including type 2 diabetes — by 78 percent.
3.Your Memory Fails You
The process of brain growth, or neuroplasticity, is believed to underlie your brain's capacity to control behavior, including learning and memory. However, sleep and sleep loss modify the expression of several genes and gene products that may be important for synaptic plasticity.
Furthermore, certain forms of long-term potentiation, a neural process associated with the laying down of learning and memory can be elicited in sleep, suggesting synaptic connections are strengthened while you slumber.
4.It's Difficult to Make Decisions
Sleep deprivation leads to accidents both big and small, some of which prove to be fatal, in part because it leads to blunted reaction times and difficulty making decisions. Participants in one study underwent two nights of total sleep deprivation followed by two nights of recovery sleep, then performed a decision-making test.
A well-rested control group (who had slept normally) performed better on the tests than the sleep-deprived group, but, worse yet, when the test rules were reversed none of the sleep-deprived volunteers got the right answer, even after 40 tries, leading the study's lead author to state their ability to take in new information was “completely devastated.”
5.Your Reaction Time Slows
In the aforementioned study, the researchers concluded that sleep deprivation is particularly problematic for decision-making involving uncertainty and unexpected change. This leads to blunted reaction times that can have tragic consequences while you're driving or on the job.
6.You're Overly Emotional
Lack of sleep kicks your emotions into high gear, which means you're likely to overreact when expressing emotions like fear and anger. Your brain's frontal cortex, for instance, plays a key role in the regulation of emotions, and sleep is vital for its function. Not to mention that research shows even one night of too little sleep may lead to unwanted behavior at work the next day, such as acting rude toward co-workers, theft or going home early without notifying the boss.
7.You're Always Getting Sick
Sleep deprivation has the same effect on your immune system as physical stress or illness, which may help explain why a lack of sleep is tied to an increased risk of numerous chronic diseases and acute illnesses like colds and flu.
In fact, research shows adults who sleep less than six hours a night have four times higher risk of catching a cold when directly exposed to the virus than those who get at least seven hours.
Sleeping less than five hours per night resulted in 4.5 times higher risk. The study found that sleep was more important than any other factor when it came to protecting against the cold virus, including stress levels, age, and smoking. In short, if you want your immune system to be at its best, adequate sleep is essential. The researchers, writing in the journal Sleep, explained:
“Growing evidence demonstrates that short sleep duration (< 6 or 7 h/night) and poor sleep continuity are associated with the onset and development of a number of chronic illnesses, susceptibility to acute infectious illness, and premature mortality. Experimental evidence in animals and humans suggests that the immune system serves as a key biological pathway.
“For instance, total and partial sleep deprivation in humans results in modulation of immune parameters critical to host resistance, including diminished T cell proliferation, shifts in T helper cell cytokine responses, decreases in natural killer (NK) cell cytotoxicity, and increased activation of proinflammatory pathways.”
8.Your Vision Seems Unfocused
Even your vision is affected by a lack of sleep. According to Health, when you're tired your ciliary muscle, which helps your eyes focus, will not work up to par and “the extraocular muscles, which move the eye from side to side and up and down, may start to track improperly, resulting in double vision.” So, if you seem to be having trouble seeing after a night of little sleep, it's probably not in your imagination.
9.Your Physical Appearance Suffers
Lack of sleep affects your physical appearance significantly, in part because it alters your hormonal balance, which can lead to acne, and decreases collagen production, which may increase the appearance of wrinkles.
Further, one study took photos of 23 people with the same hairstyles, facial expressions, and bare (no makeup) skin. The only difference between them was the amount of sleep they'd had—one group had a full night's sleep while the other group had been awake for 31 hours straight and then slept for just five hours.
Not surprisingly, when the photos were shown to a separate group of people, they rated the sleep-deprived group as less healthy, less attractive and more tired, suggesting that the idea of “beauty sleep” is not just a fairy tale.
10.You Nod Off During the Day
You might be able to fool your body into believing you can function normally on little sleep, but as reported in the journal Sleep, as soon as you let your guard down, overwhelming sleepiness ensues. Your body will likely cave into these episodes of “microsleeps” or nodding off, which can be tragic depending on your line of work or if you fall asleep while behind the wheel.
In a report released by the AAA Foundation for Traffic Safety, researchers compared driving drowsy to driving with a blood alcohol concentration considered legally drunk. Lack of sleep, even by one or two hours, nearly doubled study participants' risk of a car accident the following day. If sleep deprivation increased, with participants sleeping just four or five hours a night, their risk of a car crash quadrupled. According to the AAA Foundation for Traffic Safety:
“Previous research by the AAA Foundation for Traffic Safety has estimated as many as 7 percent of all crashes, 13 percent of crashes that result in hospital admission and 21 percent of fatal crashes involve driver drowsiness.”