Most of us know sleep is important. But many people still get less than 7 hours a night. You might think you’re fine, or that feeling a little tired is “normal.” But research shows that short sleep can affect almost every part of your health, even in ways you may not feel right away.
Here’s what happens when your body doesn’t get the sleep it needs.
Your brain doesn’t work as well
When you sleep fewer than 7 hours, your brain starts to slow down. You may not notice it, but your reaction time and focus drop. Tasks feel harder. You make more mistakes. If you drive, your risk of drowsy driving goes up.
One surprising finding: people often think they’re doing fine, even when their performance gets worse each day. That’s why sleep loss can be tricky. You may not feel very sleepy, but the risks are still there.
Your heart and metabolism take a hit
Short sleep, especially less than 6 hours, can raise your risk for heart problems. Studies link it to high blood pressure and a greater chance of heart disease.
Lack of sleep also affects how your body handles food and energy. It can:
- Lower insulin sensitivity
- Reduce glucose tolerance
- Change hormone levels that control hunger
This mix can make you hungrier, less active, and more likely to gain weight. Over time, that raises your chances of obesity, metabolic syndrome, and type 2 diabetes.
Your immune system weakens
Your body fights germs while you sleep. When you cut that sleep short, your immune system can’t work as well.
People who sleep fewer than 7 hours have:
- Lower natural killer cell activity (these cells help attack viruses and cancer cells)
- A weaker response to vaccines
- A higher chance of catching infections like colds and pneumonia
So, if you get sick more often, your sleep habits may be part of the reason.
Your mood and mental health are impacted
Sleep and mental health are strongly linked. When you don’t get enough sleep, you may feel more stressed, sad, or overwhelmed.
Short sleep is tied to:
- Higher risk of depression
- More psychological distress
- Increased thoughts of self-harm
While not every case is caused by lack of sleep, studies show that chronic short sleep can make these problems more likely to develop or worsen.
It can even affect how long you live
Studies show that adults who sleep 7 to 8 hours a night tend to live longer than people who sleep much less or much more. Both short and long sleep are linked to higher risk of death, though many other health and lifestyle factors also play a role.
Still, the pattern is clear: getting the right amount of sleep supports long-term health.
The bottom line
Routinely sleeping less than 7 hours a night can affect your brain, heart, metabolism, immune system, mood, and even your lifespan. The good news? Sleep is one of the most powerful things you can change for your health.
If you can, try to make sleep a priority. Small steps like setting a bedtime, limiting screens at night, and keeping a consistent schedule can make a big difference.
Medical review by Ahmed Saleh, MD
Additional resources
- Take a short quiz to learn how to get a better night’s sleep.
- Calculate your ideal bedtime.
- Begin and keep a sleep diary.
- Talk to your doctor about sleep.
- Get support from a sleep center.
