Millions of people sleep fewer than 7 hours each night and barely think twice about it. Whether it’s staying up for work, watching TV, or scrolling through social media, sleep often gets pushed to the bottom of the list. But
doctors and public health experts say that regularly getting too little sleep isn’t something your body just gets used to.

In fact, research shows that sleeping less than 7 hours a night puts your mental, physical, and emotional health at risk. Even if you feel okay in the moment, the long-term damage builds up quietly—and it can impact everything from your brain and heart to your hormones and skin.

You start to lose mental sharpness and emotional control

Getting less than 7 hours of sleep a night takes a toll on your brain. In fact, your memory, focus, and decision-making weaken when you’re sleep-deprived. That’s because your brain doesn’t get the time it needs to reset and clean up waste proteins. According to the National Institutes of Health (NIH), poor sleep slows down your reaction time and impairs judgment—basically, you start thinking and reacting like someone who’s had a few drinks.

Emotionally? It’s not pretty, either. You become more irritable, anxious, and easily overwhelmed. According to a book titled Sleep Disorders and Sleep Deprivation: An Unmet Public Health Problem, individuals who slept fewer than 6 hours experienced higher emotional reactivity and lower stress tolerance. Psychologists say chronic sleep loss can even raise the possibility of developing depression or anxiety disorders.

Your immune system gets weaker and easier to attack

Sleep and immunity are tightly linked. During deep sleep, your immune system releases proteins called cytokines that help you fight off infections and inflammation. When you consistently sleep less than 7 hours, your body doesn’t produce enough of these protective proteins.

According to the Mayo Clinic Expert, sleep-deprived people are more likely to catch common viruses—like colds or the flu. Some studies even show that those who sleep less are less responsive to vaccines. So if you’re staying up all night and then getting your flu shot the next morning, you may not get full protection.

Increased risk of heart ailment

It’s not just your brain and immunity. Your heart feels the pressure, too. According to the Centers for Disease Control and Prevention (CDC), not getting enough sleep increases your risk of high blood pressure, heart disease, stroke, and even heart attacks.

Why? Sleep helps regulate your blood pressure and keeps your blood vessels flexible. Without that rest period, your cardiovascular system stays in stress mode. Over time, this causes wear and tear on your heart and blood vessels.

Doctors warn that regularly sleeping less than 6 hours may even raise the likelihood of early death from cardiovascular causes.

You may gain weight even without changing how you eat

Lack of sleep disrupts your hunger hormones—ghrelin (which makes you hungry) and leptin (which makes you feel full). When you don’t get enough sleep, ghrelin goes up, and leptin goes down. This makes you crave high-calorie, sugary, and fatty foods—even when you’re not actually hungry.

The National Health and Nutrition Examination Survey (NHANES) showed that people who sleep less than 7 hours are more likely to gain weight and develop obesity over time. That’s because you’re not only hungrier but also too tired to exercise or make healthy choices. It’s a double punch: you eat more and move less.

Your risk of type 2 diabetes quietly increases

Multiple studies have shown that sleep affects how your body processes glucose (sugar). When you’re not sleeping enough, your cells become less sensitive to insulin, the hormone that helps regulate your blood sugar levels. Over time, this insulin resistance can lead to prediabetes or type 2 diabetes.

A study published in the American Diabetes Association found that even just 5 nights of restricted sleep reduced insulin sensitivity by over 24%. That means even short-term sleep loss can start messing with your blood sugar.

Your skin begins to show signs of aging faster

Poor sleep doesn’t just affect how you feel—it affects how you look. Collagen, which keeps your skin firm and smooth, is produced during deep sleep. When you consistently get less than 7 hours, your skin gets less time to repair damage from sun exposure, pollution, and stress.

Specifically, sleep-deprived individuals had more fine lines, uneven skin tone, and reduced elasticity. Basically, poor sleep speeds up the aging process, especially on your face.

Your sex drive might take a hit

If you’re always tired, your libido might suffer. That’s because low sleep is linked to lower testosterone levels in men and reduced estrogen balance in women. Both of these hormones play a major role in maintaining sexual health and arousal.

Research published in JAMA shows that men who sleep less than 5 hours per night for just one week can experience a drop in testosterone by up to 15%. For women, poor sleep affects mood, energy, and hormone balance—all of which influence sex drive.

Your long-term risk of cancer may go up

Although research is still ongoing, some evidence suggests that chronic sleep deprivation could increase your risk of certain cancers. According to the American Cancer Society, people who sleep less than 6 hours may have a slightly higher risk of colorectal, breast, and prostate cancers.

One possible explanation is that sleep helps regulate melatonin, a hormone that not only controls your sleep-wake cycle but also has antioxidant properties. Disrupting melatonin levels could interfere with cell repair and allow abnormal cells to grow unchecked.

The takeaway

Getting fewer than 7 hours of sleep a night may seem harmless, especially if you’re used to it. But doctors say it can have widespread effects on your body and brain—from your immune system and hormones to your heart, skin, and mental health.

Even if you feel “fine” running on 5 or 6 hours, the long-term effects are building in the background. Sleep isn’t a luxury; it’s a biological need. If you’re constantly shortchanging your sleep, you’re gambling with your health.