Why Sleep Matters
Sleep is not simply a period when the body shuts down. During sleep, the brain and body carry out important work involving memory, metabolism, immune function, hormones, and cardiovascular health.
The Brain
Sleep helps the brain consolidate memories and process information. Even a single poor night can affect attention, reaction time, and judgment.
Sleep is also being studied for its role in clearing metabolic waste from the brain. Poor sleep has been associated with cognitive decline and Alzheimer’s disease, although researchers are still working out how much is cause and how much is consequence.
Metabolic Health
Too little sleep can affect insulin sensitivity, appetite, and the hormones involved in hunger and satiety.
People who consistently sleep too little are more likely to develop obesity and type 2 diabetes. Sleep therefore belongs in the discussion of metabolic health alongside diet and exercise.
Heart Health
Poor or insufficient sleep has been associated with high blood pressure, cardiovascular disease, and stroke.
Sleep apnea is particularly important because repeated interruptions in breathing can reduce oxygen levels and put additional stress on the cardiovascular system.
Mood and Mental Health
Poor sleep can make people more irritable, anxious, or depressed, while anxiety and depression can themselves make sleep more difficult.
This can create a cycle in which poor sleep and emotional distress reinforce each other.
How Much Sleep Do We Need?
Most adults are advised to get about 7 to 9 hours of sleep a night, although individual needs vary.
Sleep quality matters too. Someone may spend eight hours in bed but still have poor-quality sleep because of insomnia, sleep apnea, pain, medications, or frequent awakenings.
The important question is not simply “How many hours did I sleep?” but also “Am I sleeping well enough to function and feel rested during the day?”
Learn More
What Happens During Sleep — and How to Improve It — Harvard Health
An accessible explanation of what happens in the brain and body during sleep, why the different stages of sleep matter, and how sleep affects physical and mental health.
Sleep and Older Adults — National Institute on Aging
Explains why sleep remains important as we age, how sleep patterns change, and the connections between poor sleep and memory, mood, heart health, diabetes, and daytime function.