Written by Allyson Malecha, Master of Science in Biology
Expert review by Ronee Welch, Sleep Coach and Owner of Sleeptastic Solutions

Sleep is essential to health and overall wellbeing. It gives the body the chance to recover, rest, and rebuild. Both the quality and duration of sleep impact your ability to regrow tissues, store memories, and maintain a healthy immune response, among other essential functions. You need sleep to survive and thrive, making it crucial to identify and understand how much sleep you need.

Body Maintenance and Overall Health

The amount you sleep and your sleep quality affect many of the body’s systems and processes, including metabolism, heart health, and immune health.


People commonly refer to “metabolism” as how quickly your body processes food and uses it for energy. However, metabolism consists of many different biochemical reactions in the body. These reactions release free radicals that can cause injury to your cells. The time spent asleep allows your body to repair the damage done during your waking hours.

When you sleep, you require less energy, and therefore your metabolic rate slows in alignment with your circadian rhythms.

Cortisol Levels

The stress hormone cortisol is released while you are awake. This release is accompanied by higher rates of glucose utilization, which you need for energy.

However, when your circadian rhythms are out of sync, cortisol levels can become too high for what you currently need for energy. Over time, this can contribute to increased glucose in the bloodstream, leading to a risk of developing Type 2 diabetes.

Heart Health

Sleep also has an impact on heart health as blood pressure decreases while you sleep. Poor-quality sleep or a lack of sleep maintains high blood pressure, increasing the risk of heart disease and stroke. Too few hours of sleep can also increase the risk of heart attack, as insufficient sleep is associated with calcium buildup in the arteries, leading to plaques.

The Immune System

The immune system needs sufficient sleep to function optimally. T lymphocytes (more commonly known as T-cells) are the immune cells responsible for identifying cells infected by pathogens. When T-cells recognize a virus-infected cell, they activate proteins called integrins that allow the T-cell to attach to the infected cell and kill it. In the case of bacteria, T-cells can identify bacterial fragments and produce anti-inflammatory cytokines that allow other immune cells to activate and prevent future growth of bacteria.

In a 2019 study, those who slept had higher integrin activation levels than those who stayed awake. Researchers believe this is because stress hormone levels decrease while you sleep, and cytokines and integrins cannot function as well when higher levels of stress hormones are present.

Cognition and Mental Health

Just as sleep impacts physical health, it plays an essential role in cognitive health. A review of cognitive performance studies found those who were sleep-deprived performed worse on many tasks, including reaction time, listening, visual tasks, and multitasking.

Sleep also plays a role in memory, impacting both episodic memory (your ability to recall events from your life) and your ability to recognize and recall information. Selective focus, such as paying attention to one conversation in a room full of people, is also negatively impacted by lack of sleep.

Among those who do not sleep enough, feelings of irritability, stress, and anger increase, even after only a week of mild to moderate sleep deprivation. However, if sleep is interrupted for longer periods, more significant mental health problems can occur.

Between 65 to 90 percent of adults with depression report having difficulty sleeping. Previously, sleep issues associated with depression were thought to be a symptom, but more recent research suggests that sleep disorders like insomnia may also be a predictor of depression.

Lack of sleep is also thought to contribute to anxiety, creating a cycle in which lack of sleep contributes to anxiety, and worsening anxiety impacts sleep quality. Other mental health conditions like attention-deficit/hyperactivity disorder (ADHD), bipolar disorder, and post-traumatic stress disorder (PTSD) can also worsen with insufficient sleep.

Chart showing how many hours of sleep you need at every age

Understanding Your Sleep Needs


The Centers for Disease Control and Prevention (CDC) has different recommendations for sleep based on age. For adults aged 18 to 60, seven or more hours a night is recommended. The CDC recommends between seven and nine hours for those 61 to 64 and seven to eight hours for those aged 65 and over.

There is some debate as to whether older adults need less sleep than younger individuals. Research suggests that it may be more difficult for older adults to meet their sleep needs due to other factors associated with aging. Although more sleep may be beneficial, the fact remains that it is physiologically difficult for older adults to sleep longer.

Children and Teens

Children and teens need more sleep than adults. Newborns require 14 to 17 hours, which decreases to 12 to 16 hours for infants between four and 12 months of age. Toddlers one to two years of age require 11 to 14 hours, and preschoolers require 10 to 13 hours. For younger children, these sleep recommendations include time spent napping.

School-age children between six and 12 require nine to 12 hours, and teens between 13–18 require eight to 10 hours.

Short-term Effects of a Bad Night’s Rest

While many studies on sleep deprivation look at the impact of too little sleep over a long period, even one night of bad sleep can negatively impact many aspects of your life.

In the short-term, too little sleep can cause impaired memory, stress, and lack of alertness. The inability to focus and slower reaction time resulting from a poor night’s sleep can be quite dangerous—the Department of Transportation estimates that driving drowsy is responsible for nearly 6,000 car accidents a year.

While you shouldn’t overlook the impact of a bad night’s sleep, it’s important to remember that even with the best sleep practices, a night of poor sleep here and there still may occur.

If your alarm sounds and you know you barely slept last night, resist the urge to hit snooze. Although tempting, sleeping in can throw off your circadian rhythm and can result in future nights of poor sleep.

One way to power through the morning is to get up, get out of bed, drink a glass of water, and get some sunshine. If you’re a coffee (or tea) drinker, remember to drink in moderation, as too much caffeine can cause problems sleeping later that night.

If the afternoon slump hits, an afternoon nap of 15 to 30 minutes can increase alertness and productivity but don’t forget to set an alarm.

Alternatively, a 10–minute workout can boost energy levels. No need to run sprints or do burpees—even walking stairs at a slow-to-moderate pace is sufficient.

Finally, resist the urge to go to bed too early. In the same way that sleeping in can alter your circadian rhythm, going to bed too early might impact future sleep.

What Happens If You Don’t Get Enough Sleep?

Although often referred to synonymously, sleep deprivation and insomnia are not the same. Sleep deprivation is a broad term for a long-term lack of sleep or not getting the right type of sleep for your body.

Insomnia, on the other hand, is a disorder classified by the inability to fall asleep or stay asleep and the inability to go back to bed after waking up too early. Many people experience acute insomnia, lasting only a few days or weeks, during stressful times in their lives or other difficult events. However, chronic insomnia, lasting a month or more, can result from other medical conditions or medications.

Sleep Deprivation

Sleep deprivation, also referred to as sleep deficiency, impacts a significant amount of the population. According to data from the American Sleep Association, 37 percent of U.S. adults aged 20 to 39 and 40 percent of those aged 40-59 report short sleep duration. Common symptoms of sleep deprivation include:

  • Fatigue
  • Moodiness
  • Decreased concentration
  • Lower libido

The effects of sleep deprivation can include:

  • Decreased immune function
  • Weight changes
  • Hormone changes
  • Increased risk of vascular disease, depression, anxiety, hypertension, and diabetes


As sleep deprivation and insomnia have many similar symptoms and effects, this leaves many asking, what is insomnia?

Those who have insomnia have difficulties falling asleep, staying asleep, or falling back asleep after waking up early. Both acute (lasting days or weeks) and chronic (lasting a month or more) forms of insomnia exist. About 30 percent of the American population is affected by acute insomnia during their lives, and 5 to 10 percent are affected by chronic insomnia.

While there are some shared symptoms between insomnia and sleep deprivation, there are distinct symptoms associated with insomnia.

Common symptoms of insomnia include:

  • Not feeling well-rested after a full night’s sleep
  • Worries about sleep (whether you are getting enough or whether you will be able to fall asleep)
  • Irritability, fatigue, and decreased concentration

Many of those who have insomnia have other conditions in tandem, such as depression, anxiety, or sleep apnea. Women are more likely to have insomnia than men, potentially as a result of hormonal changes due to menstruation, pregnancy, or menopause.

Additionally, insomnia can present as a symptom of depression, anxiety, or fibromyalgia, all of which impact more women than men.

Insomnia Treatment

Your doctor may recommend cognitive behavioral therapy (CBT), medications, or a combination of the two to treat insomnia. CBT focuses on training your brain to eliminate negative thought patterns that keep you awake. It helps you recognize beliefs or behaviors that keep you awake while promoting relaxation techniques, breathing exercises, and other habits to help you sleep better.

Doctors may recommend over-the-counter medications that induce drowsiness or prescribe approved sleeping pills long-term use to treat insomnia.

Dreams of Better Sleep

Knowing how much sleep you need and what you can do to get better-quality sleep is key to treating your body well. Despite the challenges of busy schedules, stress, and the unpredictable elements of daily life, getting adequate sleep should be a priority. Without it, how can you expect your body and mind to perform at their peak?