Participants and methods
The NSF assembled a multidisciplinary expert panel comprised of both sleep experts and experts in other areas of medicine, physiology, and science. This approach provided varying perspectives regarding sleep duration. The 18-member expert panel included 12 representatives selected by stakeholder organizations and 6 sleep experts chosen by the NSF. Stakeholder organizations included the following: American Academy of Pediatrics, American Association of Anatomists, American College of Chest Physicians, American Congress of Obstetricians and Gynecologists, American Geriatrics Society, American Neurological Association, American Physiological Society, American Psychiatric Association, American Thoracic Society, Gerontological Society of America, Human Anatomy and Physiology Society, and Society for Research in Human Development.
A systematic literature review was conducted by a nonvoting, independent review team led by John Herman, PhD, from the University of Texas Southwestern Medical Center at Dallas, with assistance from colleagues Chelsea Vaughn, PhD, and David Brown, PhD. They conducted the literature review using search terms and protocol agreed upon by the panel (see Table 1 for search terms). Inclusion criteria were (a) normal, nondisordered population; (b) published in a peer-reviewed journal; (c) human subjects; and (d) English language. The review focused on medical and scientific research regarding (1) sleep duration data, (2) effects of reduced or prolonged sleep duration, and (3) health consequences of too much or too little sleep. Articles were identified with searches of current indexed literature published from 2004 to 2014.
Table 1Search terms for literature review.
Primary search terms | Age search terms | Outcome search terms |
---|---|---|
Sleep time Sleep need Sleep requirement Health sleep Sleep schedule Sufficient sleep Insufficient sleep Sleep deprivation Sleep restriction Short sleeper Long sleeper | Infant Children Child Pre-school child Perschoolers Adolescent Teenager Teen Adult Senior Elderly Developmental Geriatric Newborns Toddlers School-age children | Performance Executive function Cognition Mood Learning Memory Accidents Attention deficit Academic performance Impulse control Anxiety Suicide Divorce Health Mortality Morbidity Hypertension Stroke Cerebrovascular insult Heart disease Myocardial infarct Coronary artery disease Diabetes Obesity Glucose intolerance Lipids Pain |
Fifty-eight searches using combinations of search terms related to sleep (eg, time, duration, and sufficiency), age groups (eg, newborn, adolescent), and outcomes (eg, performance, executive function, cognition) yielded 2412 articles. The review team identified 575 articles for full-text review. Of the 575 articles, 312 met our inclusion criteria. Pertinent information (eg, sample size, study design, results) from each article was extracted and included in the literature review materials. Articles were sorted based on the strength of the study and presented in descending order in a summary chart. Expert panel members received print and electronic versions of the literature.
To develop the sleep duration recommendations, the expert panel used a 2-round modified Delphi RAM to synthesize scientific evidence and expert opinion. Panelists graded every possible sleep time duration for appropriateness (ie, 0-24 hours). Response options were appropriate (ie, the expected health benefits exceed the expected negative consequences), inappropriate (ie, the expected negative consequences exceed the expected health benefits), or uncertain.
The appropriateness scale ranged from 1 to 9, with 1 representing “extremely inappropriate number of hours of sleep” and 9 representing “extremely appropriate number of hours of sleep.” Panelists rated overall health as well as cognitive, physical, and emotional health. Panelists also noted whether scores were based on convincing scientific evidence, weaker scientific evidence, expert opinion, or their own experience.
The panel agreed to the following age categories:
- •Newborn: 0-3 months
- •Infant: 4-11 months
- •Toddler: 1-2 years
- •Preschooler: 3-5 years
- •School-age: 6-13 years
- •Teenager: 14-17 years
- •Young adult: 18-25 years
- •Adult: 26-64 years
- •Older adult: ≥65 years
In total, the expert panel met 4 times over the course of 9 months and participated in 2 rounds of voting. Panelists performed the first-round vote independently. They received all 312 full-text articles, score sheets, and instructions by mail and electronically. Panelists were expected to use the provided literature to grade the appropriateness of every hour of sleep (ie, 0-24) for every age category (eg, how appropriate or inappropriate is X hours of sleep for a teenager?). A research assistant performed data entry, and a supervisor checked entries to ensure accuracy and completeness. A project team member followed up with panelists to resolve missing or discrepant scores.
The second vote occurred during an in‐person meeting. Panelists received an individualized document showing the overall expert panel’s first-round ratings, score distributions, and their own first-round votes. Panelists discussed the first-round ratings and the literature, focusing on areas of disagreement. Panelists voted at the conclusion of each age group discussion. When possible, consensus was reached; but no effort was made to eliminate disagreement.