The CDC recommends at least seven hours of sleep a night for adults. Falling short is not just fatigue. NHLBI-funded research links consistently short sleep to higher risk of obesity, high blood pressure, diabetes, coronary heart disease and stroke.
A comprehensive review published on June 9, 2026 in Frontiers in Neurology walks through those effects system by system.
Sustained short sleep, the authors write, disturbs the nervous, cardiovascular, respiratory, digestive, immune and endocrine systems at the same time.
What it does to your brain
The review points to disrupted thalamic activity and shifts in synaptic plasticity, the brain's ability to strengthen or weaken connections between nerve cells with experience.
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The practical read-out shows up in daily life. Attention, working memory, alertness, judgment, decision-making and emotional stability all take a hit.
What it does to your heart
Short sleep tips the balance between the sympathetic and parasympathetic nervous systems, the two arms that drive stress and recovery. Coronary blood flow drops.
Over time, the review links sleep deprivation to hypertension (high blood pressure), atherosclerosis (hardening of the arteries), arrhythmia and heart attack.
What it does to your immune defenses
Human studies cited in the review show elevated blood levels of two pro-inflammatory messenger proteins, IL-6 and TNF-alpha, after sleep restriction.
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The authors also flag lower activity of natural killer (NK) cells, immune cells that patrol for infected and cancerous cells, and reduced CD4+ lymphocyte activity.
A separate 2025 review in the International Journal of Molecular Sciences reaches the same conclusion on IL-6 and TNF-alpha rising after sleep loss.
What it does to your metabolism and hormones
Undersleeping alters how the body handles glucose (blood sugar) and shifts appetite hormones. Leptin, which signals fullness, falls. Ghrelin, which drives hunger, rises.
The Frontiers authors write that these changes reduce a person's ability to control blood sugar after sleep loss and raise the risk of type 2 diabetes.
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NHLBI describes the same pattern in plain terms. When you sleep less, ghrelin goes up, leptin goes down, and blood sugar runs higher than normal.
What counts as enough
The National Sleep Foundation, cited in the review, sets the floor at seven hours a night for adults. The CDC's recommendation matches that.
Yet CDC data show a large share of US adults still fall below that mark, with rates of insufficient sleep running from about 30 percent in Vermont to 46 percent in Hawaii in 2022.
Anyone with persistent trouble sleeping should talk to their doctor rather than manage it alone.
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This article is made and published by Ida-Marie Palm Varbæk, who may have used AI in the preparation.