What is short sleep syndrome? The rare condition that causes a lucky few, like Barack Obama, to only need 6 hours of sleep a night

https://www.msn.com/en-xl/health/wellness/what-is-short-sleep-syndrome-the-rare-condition-that-causes-a-lucky-few-like-barack-obama-to-only-need-6-hours-of-sleep-a-night/ar-BB16SyjM?ocid=msedgdhp

Short sleep syndrome is a condition that allows 1% of the population to operate on less than six hours of sleep with no daytime difficulties.
People who are short sleepers also exhibit signs of hypomania, impulsivity, and a high reward drive.
Short sleep syndrome is not to be confused with a condition like insomnia, which causes people to get very little sleep but suffer daytime tiredness. 
This article was medically reviewed by Alex Dimitriu, MD, psychiatrist and founder of Menlo Park Psychiatry and Sleep Medicine. 
Visit Insider's Health Reference library for more advice.
People with short sleep syndrome sleep 4-6 hours per night and still feel well-rested and alert the next day. Though this rare condition affects roughly one percent of the population, there are a number of well-known people who claim to regularly operate on very little sleep, including Barack Obama, Martha Stewart, and Jack Dorsey, the founder of Twitter. 
Here's what you need to know about short sleep syndrome, including its symptoms, causes, and treatments.
Overview of short sleep syndrome
Sleep experts may refer to a person with short sleep syndrome as a "habitual short sleeper" (HSS) and "natural short sleeper (NSS)," says Paula G. Williams, PhD, associate professor in the department of psychology at University of Utah  who has studied short sleepers.


Although approximately 30% of Americans report regular bouts of short sleep, many are not short sleepers from a clinical standpoint since they do not feel well-rested the next day. 


The primary symptom of short sleep syndrome is consistently sleeping six hours or less and feeling fully functional the next day. However, from her research Williams has found other traits that tend to be consistent among most short sleepers.


"Those who do not report daytime dysfunction related to their short sleep and are characterized by hypomania, impulsivity, and high reward drive would meet the criteria of a short sleeper," says Williams. "They tend to engage in stimulating activities that allow them to override sleepiness."


Williams says short sleep syndrome is much different than a condition like insomnia. For example, people with insomnia would be characterized by higher anxiety. "These individuals usually report fatigue, non-restoration, and dissatisfaction with their short sleep," she says.


How short sleep syndrome is diagnosed 
Many people with short sleep syndrome may not seek a diagnosis from a doctor because they aren't experiencing adverse health effects, says Lynelle Schneeberg, PsyD, an assistant professor at Yale School of Medicine and American Academy of Sleep Medicine Fellow. 


However, you may be suffering from lack of sleep and not even realize it. So, if you're getting 6 hours of sleep a night or less, it's important to get a diagnosis, Shneeberg says. "It would be ideal to rule out insomnia and other medical sleep disorders, such as sleep apnea, which can cause disrupted sleep."


When making a diagnosis, a doctor will look for common behaviors that people with short sleep syndrome tend to exhibit:


They usually have had this sleep pattern most of their lives, since childhood or young adulthood, and are a short sleeper regardless if it's a weekday, weekend, or during a vacation.
They don't use sleep aids to fall asleep — they just naturally fall asleep around the same time each night, sleep six hours or less, and wake up around the same time each day feeling alert.
Short sleepers instinctually tend to sleep set hours each night. Conversely, someone with a sleep disorder may report waking up several times in the night and not feeling rested the following day.
Schneeberg says anyone experiencing irregular sleep patterns could benefit from a "sleep checkup." In this case, they may be asked to track their sleep via an app, such as CBT-i Coach, a wrist-worn wearable device, or a handwritten sleep log which you can download from an organization like the American Academy of Sleep Medicine (AASP).


After tracking their sleep patterns for 14 days, the doctor may order an electroencephalogram (EEG), which would record the person's brain waves. At the same time, their heart functioning would be collected through electrocardiography (ECG). These would both help in making an assessment about someone's sleep health and whether or not they are a short sleeper or if their brain activity indicates a sleep disorder such as insomnia.


The causes of short sleep syndrome
Little is known about the cause of short sleep syndrome, but researchers have found convincing evidence that at least part of it is genetic. 


One of the leading researchers in this field is Ying-Hui Fu, PhD, a professor of neurology at the University of California, San Francisco, and a member of the UCSF Weill Institute for Neurosciences who has been studying short sleepers for nearly 25 years. Which is no easy feat since they make up about 1% of the population.


Over the years, she has discovered a few of what she calls "short sleep" genes:


In 2009, Fu and her fellow researchers identified a genetic mutation, DEC2, known to affect circadian rhythms.


After doing DNA screenings on several hundred blood samples from 70 families of people who had participated in sleep studies, they found the mutation in two people, a mother and a daughter. Both exhibited common symptoms of short sleepers because they averaged approximately 6.25 hours of sleep per night, slept from about 11 p.m. to 5 a.m. each night, and felt functional the next day.


Fu and her colleagues then further tested DEC2 in animals. The scientists bred mice and fruit flies with the same mutation and they slept less, and recovered faster, than mice and fruit flies without the mutation.