Protocol · graded by use, four uses
Sleep duration: how much sleep a night, from sleep extension to keeping 7 hours or more
Graded on: energy intake, blood pressure and insulin sensitivity after sleep was lengthened or cut.
Grade C: human trials exist, but they are small, mixed or not yet repeated. This is not a finding that it does not work. How to read a grade →
At a glance
This page is about how much sleep, not a sleep aid. When people who slept too little were helped to sleep about an hour longer, one study found they ate less. Two small studies found lower blood pressure, and others found no change. Blood sugar control did not improve in the biggest studies. When people who slept enough were made to sleep about an hour and a half less, their bodies handled insulin worse, in studies from four separate teams. No study has tested sleep length against heart attacks or death. Links between about 7 hours of sleep and a longer life come from studies that only watched people.
- What was measured
- Calories eaten each day, measured objectively rather than from food diaries, in adults with overweight who slept under 6.5 hours.
- How big
- The group that slept about 1.2 hours more ate about 270 fewer calories a day.Read from the summary of PMID PubMed ID: the permanent number the US National Library of Medicine gives a published paper. Each one links to that paper's record on PubMed. 35129580.
- Who it applies to
- Adults aged 21 to 40 with overweight who slept too little, over 2 weeks. It says nothing about adults who already sleep 7 hours or more.
- Safety
- The trials report no harm from sleeping longer at the amounts studied.
- Compared with
- A group that kept its usual sleep.
- Certainty
- Grade C, resting on: Randomized trials that lengthened sleep in short sleepers, randomized trials that cut sleep in people who slept 7 hours or more, and a pooled analysis of the latter; no trial has tested sleep length against death or heart events.
- What would change this grade
- Could rise to B with: Randomized trial lengthening sleep by at least an hour a night in short sleepers, by a group independent of the cited trials, with energy intake measured objectively and blood pressure by 24-hour monitoring. Who: Adults with overweight sleeping under 6.5 hours, at least 100 per arm. Measured: Energy intake and 24-hour blood pressure. Length: At least 3 months.
- Cost
- No price recorded yet.
- Sources
- 15 studies cited on this record, listed under Sources.
All four uses graded on this record carry a C, each on its own evidence.
This record carries a separate letter for each thing it has been measured on. The headline grade is the best of them, and it does not transfer to the others.
Tasali et al. (JAMA Intern Med, 2022; PMID 35129580) randomized 80 adults with overweight who slept under 6.5 hours to one sleep hygiene session aimed at 8.5 hours in bed, or to their usual sleep, for 2 weeks. Sleep rose about 1.2 hours a night and energy intake, measured objectively rather than from food diaries, fell by about 270 kcal a day against the control group. Al Khatib et al. (Am J Clin Nutr, 2018; PMID 29381788), in 42 normal-weight short sleepers over 4 weeks, found lower free sugar intake from 7-day food diaries, a self-reported measure, and no difference in markers of energy balance. Energy intake is a marker, and the measured result is one trial that has not been independently repeated: C.
Baron et al. (J Clin Sleep Med, 2019; PMID 31739848) randomized 16 adults with short sleep and high-normal or stage 1 blood pressure to a 6-week coached sleep extension program or self-management; 24-hour systolic and diastolic pressure fell more with the program. Hartescu et al. (J Sleep Res, 2022; PMID 34459060), 18 men with overweight or obesity, found systolic pressure fell 11.09 mmHg with 6 weeks of sleep extension against a 0.76 mmHg rise in controls. Haack et al. (J Sleep Res, 2013; PMID 23171375), a pilot, found pressure fell in the extension group but the fall did not differ from the sleep maintenance group. Gonzales et al. (Sleep Med, 2022; PMID 35180478) found five nights of extended sleep did not change night or morning blood pressure in midlife adults. Blood pressure is an established marker, but these are small trials with mixed results: C.
The largest and best-measured trials found no benefit. Beals et al. (Diabetes Care, 2026; PMID 41564347) extended sleep by about 1.1 hours a night for about 6 weeks in adults with overweight or obesity and insulin resistance and found no difference in insulin sensitivity measured by the hyperinsulinemic-euglycemic clamp, or in glycemic control. So-Ngern et al. (J Clin Sleep Med, 2019; PMID 31053213), a crossover A trial design in which each participant receives both the treatment and the comparison, one after the other, and serves as their own control. in 21 adults, found no effect of 2 weeks of extension on any metabolic measure. Malone et al. (Nurs Res, 2026; PMID 42910621) added a sleep program to a lifestyle program in 196 adults with prediabetes and found no difference in glucose. One small trial found a benefit: Hartescu et al. (J Sleep Res, 2022; PMID 34459060), 18 men, HOMA-IR improved. Mixed results on a marker: C.
Trials that cut sleep in people who sleep enough, from four independent groups, found insulin sensitivity fell. Zuraikat et al. (Diabetes Care, 2024; PMID 37955852), 38 women, 6 weeks of sleep cut by about 1.34 hours a night: fasting insulin and HOMA-IR rose. Buxton et al. (Diabetes, 2010; PMID 20585000), 1 week of 5 hours a night: insulin sensitivity by clamp fell 11%. Rao et al. (J Clin Endocrinol Metab, 2015; PMID 25658017): whole-body insulin sensitivity fell 25%. Nedeltcheva et al. (J Clin Endocrinol Metab, 2009; PMID 19567526): insulin sensitivity and glucose tolerance fell with 5.5 hours in bed. Sondrup et al. (Sleep Med Rev, 2022; PMID 35189549) pooled 21 sleep restriction trials with the same direction. The finding replicates, but insulin sensitivity is not one of the established stand-ins for a clinical outcome that Grade B names, so the use holds at C.
Energy intake when short sleep is lengthened in adults with overweight (C, one trial). Blood pressure when short sleep is lengthened (C, small trials, mixed). Insulin sensitivity and glucose when short sleep is lengthened (C, mixed; the largest trials found no benefit). Insulin sensitivity when a usual 7 hours or more is kept rather than cut by about 1.5 hours (C; replicated The same finding reproduced by a separate research group. A result seen once can be chance or bias; a replicated one is harder to explain away., on a marker Grade B does not name).
Why this letter
Why this gradeGrade C, small or unreplicated trials. The reasoning, and what the grade does not cover.
Grade C on every use. Lengthening sleep in people who slept too little: energy intake fell in one trial with objective measurement (Tasali 2022, PMID 35129580) that no other group has repeated; blood pressure fell in two small trials (Baron 2019, PMID 31739848; Hartescu 2022, PMID 34459060) and did not differ in a pilot or in five-night extension (Haack 2013, PMID 23171375; Gonzales 2022, PMID 35180478); insulin sensitivity did not improve in the largest and best-measured trials (Beals 2026, PMID 41564347; Malone 2026, PMID 42910621; So-Ngern 2019, PMID 31053213) against one small positive trial (Hartescu 2022, PMID 34459060). These are thin or mixed results on markers, which is the definition of C. Cutting sleep by about 1.5 hours a night in people who slept 7 hours or more lowered insulin sensitivity in trials from four independent groups (Zuraikat 2024, PMID 37955852; Buxton 2010, PMID 20585000; Rao 2015, PMID 25658017; Nedeltcheva 2009, PMID 19567526). That finding replicates, but the written definitions accept a marker above C only when it is an established stand-in for a clinical outcome, such as HbA1c A blood test that reflects average blood sugar over the previous two to three months., LDL Low-density lipoprotein cholesterol, the cholesterol fraction most closely tied to plaque in the arteries., blood pressure or bone density, and insulin sensitivity is not one, so the use holds at C. No randomized trial has tested sleep length against death or heart events; the link between about 7 hours and longer life comes from cohorts and carries no letter.
WHAT THIS GRADE DOES NOT COVERsleep aids, sleep apnea treatment, sleep timing or insomnia therapy, each graded on its own record; children and adolescents, whose sleep trials are outside this record; and whether sleeping longer than 9 hours helps or harms, which no trial here tested.
A grade describes the human evidence for a named use. It is not advice, and it is not a judgment on any individual prescription. How the letters are decided →
Trials report an average. This box says whether any trial on this record looked at who the result applies to, and what it found.
For this record's Grade C · Subgroup tested, effect differedZuraikat et al. (Diabetes Care, 2024; PMID 37955852) reported that insulin resistance rose more with cut sleep in postmenopausal than in premenopausal women (P for interaction 0.042). A subgroup result shows who the effect appeared in within these trials. It does not change the letter. This subgroup was identified after the results were in and has not been confirmed in a trial designed to test it.
Evidence notes: randomized trial, mixed
Endpoint The outcome a trial measures to decide whether the treatment worked, such as heart attacks, blood pressure or a symptom score. graded: Energy intake, blood pressure and insulin sensitivity after sleep was lengthened or cut (surrogate)
Last reviewed: November 2026
The trial that would change this grade.
A positive trial of this shape, supported by further trials, would move this entry to B.
Why the current trials fall short
The lengthening uses rest on one trial for energy intake and on small, mixed trials for blood pressure. A larger independent trial confirming lower 24-hour blood pressure, an established marker, would support raising that use; a null result would leave the lengthening uses resting on mixed and null trials.
ClinicalTrials.gov, the public registry run by the U.S. National Library of Medicine, lists studies that are recruiting volunteers. The link below searches it for Sleep Duration among studies recruiting now. EBL has no relationship with any listed study and receives no payment for this link.
Search recruiting studies of Sleep Duration on ClinicalTrials.gov
Dose, form and timing
Measured outcomes in the graded trials: energy intake measured objectively (PMID 35129580), 24-hour and office blood pressure (PMIDs 31739848, 34459060), and insulin sensitivity by clamp or glucose tolerance test (PMIDs 41564347, 20585000). Sleep was measured with a wrist actigraph in most trials to count the dose; it was not an outcome.
As studiedDose, form, population and duration for every use.
A grade describes the intervention that was tested. Where the product on the shelf differs from it, this says so.
Safety
Lengthening sleep was well tolerated in the trials above. In one small pilot that pushed time in bed about 2 hours past habitual sleep in people who already slept normally, mood was lower and interleukin-6 rose (Reynold 2014, PMID 25374963).
No safety data. Each caution on this record, sorted by what it rests on.
None recorded.
None recorded.
None recorded.
None recorded.
No safety data: EBL has found no trial or report of harm for this record. That is an absence of evidence, not a finding of safety.
Grade history
How this letter has changedLatest: No. 437 · November 2026 · First graded.
How much sleep now has its own record, graded by use. Lengthening sleep in people who slept too little: energy intake fell in one trial, Tasali et al. (JAMA Intern Med, 2022; PMID 35129580): C. Blood pressure fell in two small trials, Baron et al. (J Clin Sleep Med, 2019; PMID 31739848) and Hartescu et al. (J Sleep Res, 2022; PMID 34459060), and did not differ in others: C. Insulin sensitivity did not improve in the largest trials, Beals et al. (Diabetes Care, 2026; PMID 41564347) and Malone et al. (Nurs Res, 2026; PMID 42910621): C, mixed. Cutting sleep by about 1.5 hours in people who slept 7 hours or more lowered insulin sensitivity in trials from four independent groups, including Zuraikat et al. (Diabetes Care, 2024; PMID 37955852): C, because insulin sensitivity is not an established stand-in that Grade B names. No randomized trial has tested sleep length against death or heart events.PMID 35129580 PMID 31739848 PMID 34459060 PMID 41564347 PMID 42910621 PMID 37955852
Every change to a letter on this site is dated and published. The full evidence log →
Sources
- Citations
- Every paper cited on this page is matched to its PubMed record on every build.
- Retractions
- None of these papers is retracted or under a journal expression of concern. PubMed is checked again on every build.
- Read against the papers
- November 2026. By a language model (AI-assisted reading), not yet reviewed by a clinician.
- Outside review
- Not yet done. No reviewer outside EBL has checked this record.
What each of these checks can and cannot show: evidence integrity.
The evidence, in full15 papers, each linked to its PubMed record.
Graded by use, because lengthening short sleep and cutting adequate sleep are different questions. Lengthening sleep: Tasali et al. (JAMA Intern Med, 2022; PMID 35129580), energy intake; Al Khatib et al. (Am J Clin Nutr, 2018; PMID 29381788), food diaries; Baron et al. (J Clin Sleep Med, 2019; PMID 31739848), Hartescu et al. (J Sleep Res, 2022; PMID 34459060), Haack et al. (J Sleep Res, 2013; PMID 23171375) and Gonzales et al. (Sleep Med, 2022; PMID 35180478), blood pressure; Beals et al. (Diabetes Care, 2026; PMID 41564347), So-Ngern et al. (J Clin Sleep Med, 2019; PMID 31053213) and Malone et al. (Nurs Res, 2026; PMID 42910621), insulin sensitivity and glucose. Cutting sleep: Zuraikat et al. (Diabetes Care, 2024; PMID 37955852), Buxton et al. (Diabetes, 2010; PMID 20585000), Rao et al. (J Clin Endocrinol Metab, 2015; PMID 25658017), Nedeltcheva et al. (J Clin Endocrinol Metab, 2009; PMID 19567526), and the pooled analysis by Sondrup et al. (Sleep Med Rev, 2022; PMID 35189549). Reynold et al. (J Sleep Med Disord, 2014; PMID 25374963) is cited for a caution only.
How EBL searched for the trials (1 search)
The search that was run, what it returned, and what was left out and why, so the absence of evidence can be checked as well as its presence.
("sleep extension"[tiab] OR "extending sleep"[tiab] OR "extended sleep"[tiab] OR "sleep duration"[tiab] OR "increase sleep"[tiab] OR "increasing sleep"[tiab]) AND (randomized controlled trial[pt] OR randomized[ti] OR randomized[ti]) AND ("short sleep"[tiab] OR "short sleepers"[tiab] OR "habitual short"[tiab] OR "insufficient sleep"[tiab] OR extension[ti])PubMed watch: does a new study change the grade? (nothing new)
No new paper matching the searches behind this grade has been added to PubMed since November 2026.
Last run November 2026. A letter on EBL moves only after a logged review. A new paper never moves a letter by arriving: it is read, the answer is written here, and any change to the letter is published in the evidence log.
For each trial behind a letter on this page, the funding its PubMed record lists. "No funder" means PubMed lists none, not that the trial had no funding.
- Tasali et al., 2022, JAMA Intern Med (PMID 35129580): PubMed lists funding from US National Institutes of Health (National Institute of Diabetes and Digestive and Kidney Diseases); US National Institutes of Health (National Center for Advancing Translational Sciences). The PubMed record carries a competing-interest statement.
- Al Khatib et al., 2018, Am J Clin Nutr (PMID 29381788): PubMed lists no funder for this trial.
- Baron et al., 2019, J Clin Sleep Med (PMID 31739848): PubMed lists no funder for this trial.
- Hartescu et al., 2022, J Sleep Res (PMID 34459060): PubMed lists funding from Department of Health.
- Haack et al., 2013, J Sleep Res (PMID 23171375): PubMed lists funding from US National Institutes of Health (National Institute on Aging); US National Institutes of Health (National Center for Research Resources). The PubMed record carries a competing-interest statement.
- Gonzales et al., 2022, Sleep Med (PMID 35180478): PubMed lists funding from American Heart Association-American Stroke Association. The PubMed record carries a competing-interest statement.
- Beals et al., 2026, Diabetes Care (PMID 41564347): PubMed lists funding from US National Institutes of Health (National Heart, Lung, and Blood Institute); US National Institutes of Health (National Institute of Diabetes and Digestive and Kidney Diseases); US National Institutes of Health; US National Institutes of Health (National Center for Advancing Translational Sciences). The PubMed record carries a competing-interest statement.
- So-Ngern et al., 2019, J Clin Sleep Med (PMID 31053213): PubMed lists no funder for this trial.
- Zuraikat et al., 2024, Diabetes Care (PMID 37955852): PubMed lists funding from US National Institutes of Health (National Heart, Lung, and Blood Institute); US National Institutes of Health (National Institute of Diabetes and Digestive and Kidney Diseases); American Heart Association-American Stroke Association; US National Institutes of Health (National Institute on Aging); US National Institutes of Health (National Center for Advancing Translational Sciences). The PubMed record carries a competing-interest statement.
- “Sleep restriction for 1 week reduces insulin sensitivity in healthy men” (PMID 20585000): PubMed lists funding from US National Institutes of Health (National Center for Research Resources); US National Institutes of Health (National Institute on Aging).
- “Subchronic sleep restriction causes tissue-specific insulin resistance” (PMID 25658017): PubMed lists funding from US National Institutes of Health (National Institute of Diabetes and Digestive and Kidney Diseases); US National Institutes of Health (National Center for Advancing Translational Sciences); US National Institutes of Health (National Heart, Lung, and Blood Institute).
- “Exposure to recurrent sleep restriction in the setting of high caloric intake and...” (PMID 19567526): PubMed lists funding from US National Institutes of Health (National Institute on Aging); US National Institutes of Health (National Center for Research Resources); US National Institutes of Health (National Heart, Lung, and Blood Institute); US National Institutes of Health (National Institute of Diabetes and Digestive and Kidney Diseases).
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These statements have not been evaluated by the Food and Drug Administration. Any grade on this page describes the strength of published human trial evidence in the populations studied. It is not a recommendation for any individual and is not medical advice. Starting, stopping or changing any supplement or medication is a decision for your physician.
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