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By Moira Lawler / LearnVest
August 17, 2016
Businessman sleeping on office desk with stack of files
Westend61—Getty Images

We’d all love to have a few extra hours in the day: to score more family and friend time, complete that backlog of errands or even just get up to speed on early episodes of The Night Of.

But stealing those extra hours by pushing your bedtime to the wee hours of the morning isn’t the way to go—if you care about your performance at work, that is. Because even though you might think you’re still acing your job with a major sleep deficit, science suggests you’re only fooling yourself. And since boosting your salary is one of the fastest ways to improve your financial situation, you want to make sure you’re keeping your career on track.

A study in the journal Sleep found that subjects who racked up just six hours of snooze time per night for two weeks functioned as badly as if they were deprived of sleep for 48 hours. Here’s the thing: The study’s subjects actually thought they were performing well—not just skating by but actually doing an all-star job.

“Many people take pride in the fact that they don’t get enough sleep,” says W. David Brown, Ph.D., a sleep psychologist and author of “Sleeping Your Way to the Top: How to Get the Sleep You Need to Succeed.” It’s as if six hours a night makes you some sort of superhero, when it actually leaves your brain as addled as if you’d downed a few drinks, reports another study.

You wouldn’t arrive at work intoxicated and expect to be sharp in a brainstorming meeting, right? Yet for some reason, most of us have no problem coming to the office seriously sleep-deprived but certain that our productivity won’t suffer. Knowing all the ways extreme fatigue impacts your performance, however, might convince you to change your vampire ways. These seven consequences spell it all out.

Read More: 6 Ways Night Owls Can Thrive in a 9-to-5 Work World

Your Judgment Takes a Hit

Maybe you’ve interviewed several job candidates, but you keep going through their résumés because you can’t put a face to their accomplishments. Or your department holds an emergency meeting to decide about cutting loose a difficult client, and it’s taking you a while to size up the situation.

No wonder: An ongoing sleep deficit short-circuits the part of the brain that handles decision-making and problem-solving, says Richard Shane, Ph.D., a behavioral sleep specialist. That leads to your needing lots of time to make a judgment call.

And if you’re faced with a moral dilemma—for example, whether to give credit to a coworker who offered you an assist on a report—sleep deprivation puts you at a disadvantage. Not sleeping enough also affects your ability to make appropriate ethical judgments, finds another study published in Sleep.

Read More: Work Smarter: The Best Times of Day to Conquer Your To-Dos

You’re Moody and Irritable

Ever find yourself snapping at junior staffers or letting small things get to you—like when there’s no paper in the printer and you need your report ASAP? That irritability isn’t your office’s fault. When your sleep needs haven’t been met, exhaustion triggers crazy-rough mood swings.

Here’s the physiology: “Emotions reside in a part of the brain called the amygdala,” Brown says. The amygdala usually communicates with the cortex (which influences awareness and perception) to process emotions. But when you’re sleep-deprived, the amygdala ignores the cortex and moves straight into fight-or-flight mode, throwing logic out the window, Brown explains.

“[That results in] anger and a stronger form of irritability; you’re more stressed and you’re more depressed,” Shane says. You’re also prone to overreacting. “If you see someone who’s very sleep-deprived, they appear almost intoxicated,” Brown says. “They laugh at things that are not really that funny, or they may cry at the slightest insult or sad event.” Too little sleep could also intensify depression, finds a 2014 study.

Read More: 5 Ways Your Health Can Impact Your Financial Well-Being

You Show Up at Work but Aren’t Really There

If you log the occasional late night, the next day you feel like you appear OK on the outside, yet you’re just going through the motions in a sleepwalking haze. When you regularly skimp on sleep, however, that’s what you’re like every day.

“We’re now using a term called presenteeism, which is when employees show up to work but get very little done because they are so sleep-deprived they aren’t functioning optimally,” Brown says. These employees are physically present without really being mentally present because their brains are stuck in fatigue mode.

You’re Accident-Prone

“About 70% of accidents are human-related—they don’t happen randomly,” Brown says. A major contributing factor? You guessed it: exhaustion. “Accidents tend to occur between midnight and 6 a.m. and 2 and 4 in the afternoon,” Brown says. “Those times correspond exactly with the tendency for humans to fall asleep.”

These injuries and accidents can be crippling in a physical sense for an employee and in an economic sense for a business. Insomnia contributes to 7.2% of costly workplace accidents, amounting to $31 billion each year, reports one study. Even if you’re a desk jockey who doesn’t handle heavy machinery, lack of sleep impairs your motor skills so you’re more likely to trip and fall, scald yourself by spilling hot coffee or get into an accident during your drive to or from the office.

You Use Up a Lot of Sick Days

Sleep deprivation also affects your immune system, which means you could end up spending your coveted PTO sniffling in bed. “When you sleep poorly, you have three times the amount of sickness,” Shane says. Consistently sleeping less than six hours a night makes you more likely to catch a cold, finds a 2015 study.

Not to mention major health issues like diabetes, obesity, heart disease and high blood pressure are linked to sleep quantity, Shane says. “You have one night of poor sleep, and you notice the effects,” he says. “That’s proof right there that sleep is vitally important to your health, like exercise and nutrition.”

You Can’t Remember a Client’s Name

Try getting out the door on fewer than five hours of sleep, and you’ll be lucky to remember where you parked your car. Not getting enough sleep warps your memory. “Sleep does seem important for consolidating not just facts and figures in our memory but mechanical movements,” Brown says.

Here’s why: While you sleep, sharp-wave ripples are reactivated in the brain’s hippocampus to help you process the information you took in during the day, finds astudy in the journal Cell Reports. Getting plenty of sleep both before learning and after learning makes a difference in what and how much you recall, Brown says.

You Make a Poor Impression on Your Team

Think you’ve trained yourself to function fine on six hours’ sleep? Fatigue is pulling the wool over your eyes—and your reputation as an employee or a team leader can suffer as a result. “If you don’t think you’re more irritable, ask some of your coworkers,” Shane suggests.

As mentioned earlier, sleep-deprived professionals behave similarly to people who are intoxicated. Beyond the slowed reaction time and lack of self-control, both groups infamously deny that anything’s off. “When people are drunk, a lot of times they don’t know that they’re drunk, and they’ll tell you they’re not drunk,” Shane says. “It’s the exact same thing when people are sleep-deprived. They think everything’s OK and they can function just as well,” but their colleagues know better.