Forget about the student loan and consumer debt crises you hear about on the news. There's a new type of debt for Americans to worry about: sleep debt. Approximately, 35% of Americans get fewer than seven hours of sleep each night, and while many know they're not sleeping enough, they may not be aware of how devastating chronic lack of sleep — or sleep debt — is to their health.

What is Sleep Debt?

Sleep debt, simply put, is the gap between the amount of sleep you get, and what you should be getting each night.

For example, you're supposed to get eight hours, but regularly sleep just seven and a half hours a night (like yours truly). This means you're accruing an ongoing sleep debt of a half hour each night, or three and a half hours each week.

Multiply that by the 52 weeks that exist in a year, and you could be in 182 hours of sleep debt by the end of the year (that's a little over a week in missed sleep.)

And that assumes you sleep perfectly each and every night of the year. Many Americans accrue a massive sleep debt each month, unaware of how far they've fallen behind and how the effects of sleep deprivation are really hurting their lives.

The Effects of Sleep Debt

Early side effects of sleep debt are easy to spot — they are similar to signs of sleep deprivation: fatigue, irritability, inability to concentrate.

But chronic sleep debt and sleep exhaustion carry a host of scarier health issues: low immune function, higher blood pressure and higher insulin resistance. Studies also show sleep debt raises an individual's risk for obesity, stroke, diabetes and even heart disease.

With medical conditions like this, you should think twice before pulling an all-nighter on an important project.

Is Sleep Debt Cumulative?

The cumulative effects of sleep debt are powerful and demonstrated in a recent sleep study conducted by University of Pennsylvania and Harvard Medical School. The study found that the cognitive function of a group getting four hours of sleep each night for two weeks matched the function of a group of volunteers who went without any sleep for just one night.

The same study also found that while cognitive performance continued to decline, the four-hour sleep group continued to rate their sleepiness levels at about the same levels.

In short, while it may appear that you are getting used to living on little sleep, your body would say otherwise.

Can you Repay Sleep Dept?

Whether you can recover lost sleep by oversleeping is a bit controversial. Depending on where you look, the answer could be either yes or no.

First, you can definitely repay short term sleep debt; the University of Pennsylvania and Harvard Medical School study referenced above found the side effects reversed once the subjects caught up on their sleep.

However, the jury is still out on whether long-term sleep deficits are reversible. Think about it: if you've got thousands in credit card debt, it's hard to dig yourself out. The same can be said for the hours in sleep debt that rack up each year.

One of the myths around sleep debt is that it only takes a weekend of rest or a vacation to pay it all back. This is also false. In reality, it takes several snoozes over multiple days to get back to normal.

It's important to use naps to aid in short term loss of cognitive function from sleeplessness, and try sleeping an hour to two hours extra each night to make up for any deficits. If you're worried about how much sleep is too much sleep when trying to pay back your sleep debt, you can use this sleep debt calculator to get back on track and try to stay on top of your sleep debt on a weekly basis.

And of course, if you're really concerned with your sleep health, make sleep a priority in your life every day, and try not to fall into sleep debt in the first place by practicing good daily sleep hygiene!