“It is possible for a person to fully function on 5 hours of sleep per night if they train their body.”

“Adults should sleep 7 or more hours per night on a regular basis to promote optimal health. Sleeping less than 7 hours per night on a regular basis is associated with adverse health outcomes, including weight gain and obesity, diabetes, hypertension, heart disease and stroke, depression, and increased risk of death. Sleeping less than 7 hours per night is also associated with impaired immune function, increased pain, impaired performance, increased errors, and greater risk of accidents.”

“Regular physical activity can lead to improved sleep quality, reduced sleep latency, and better overall sleep quality. Studies have also found that moderate physical activities enhance overall sleep length, decrease sleep latency, and reduce the number of nightly awakenings. Most studies in our review that reported on high-intensity physical activities found that it exerted an opposite effect on sleep quality, leading to difficulties in falling asleep.”

“Most adults need about 7 to 8 hours of good-quality sleep per night... Researchers are conducting genetic studies and have identified gene mutations in some people who naturally sleep 6 or less hours a day and appear healthy and function well. ... The percentage of the population with these gene mutations is estimated to be small. Most people who say they do not need much sleep are pushing themselves to sleep less and as a consequence struggle to stay awake and function during the daytime.”

“The daily recommended hours of sleep you need changes as you age. ... For adults aged 18–60 years, 7 or more hours are recommended. Getting enough sleep and good sleep quality are essential for healthy sleep.”

“Scientists identified a gene that causes people to naturally sleep less than six and a half hours each night without any apparent ill effects. The findings reveal a mechanism affecting quality sleep and suggest an avenue to investigate for new sleep treatments.”

“Researchers analyzing nationwide data found that insufficient sleep was more closely tied to shorter life expectancy than diet, exercise, or loneliness. The connection was consistent year after year and across most U.S. states. The takeaway is simple but powerful: getting seven to nine hours of sleep may be one of the best things you can do for long-term health.”

“Short sleeper syndrome comes down to genetics. Researchers have identified several gene mutations that let some people thrive on less sleep. The first breakthrough came in 2009. Researchers discovered a mutation in the DEC2 gene — also called BHLHE41 — in a mother and daughter who slept only 6.25 hours per night. The catch? It's extremely rare. And it's genetic, not something you can train yourself to do.”

“Therefore, sleeping 5 hours each night is not enough to maintain health and work productivity. In the long run, this habit also increases the risk of cardiovascular disease, diabetes, obesity, memory impairment, weakened immune function, and shortened lifespan. There are a few people in the world who carry rare gene mutations (DEC2 or ADRB1) that allow them to function normally with 4–6 hours of sleep, but this percentage is extremely rare (<1% of the population).”

“Terry Cralle, MS, RN, and clinical sleep health educator, says, “Most adults require 7-9 hours of sleep a night, so, no, five hours of sleep is not enough.” While Cralle points out that there's a small segment of the population with a genetic variant that allows them to function well on very little sleep, she notes that those folks only amount to maybe 1 percent of the population and, by definition, are a rare breed. For the rest of us who don't have that superpower, Cralle says “people cannot 'learn' to get by on less sleep than needed or acclimate to chronic sleep debt.””

“Experts recommend adults get at least 7 hours of sleep per night for better health. Consistently getting less than 5 hours of sleep can have adverse effects on physical and mental health. Research shows that this is because individuals who are regularly sleep deprived may get used to the symptoms, not because they no longer experience the effects of sleep loss.”

“Sleep experts have determined that you can't train yourself to need less sleep. ... Getting under eight hours of sleep will likely cause your cognitive abilities to suffer. ... You'll probably feel like the 'training' is working — like you're gradually adapting to getting less rest until you're able to function just fine. But you'll be wrong.”

“After two or more nights of short sleep, people usually show signs of irritability and sleepiness. Work performance begins to suffer, particularly on complicated tasks, and people are more likely to complain of headaches, stomach problems, sore joints, memory lapses, and sluggish reaction time. Long-term partial sleep deprivation occurs when someone gets less than the optimal amount of sleep for months or years on end — a common scenario for insomniacs and people with sleep disorders.”

“There is no denying the effects of sleep deprivation. And training the body to sleep less is not a viable option. In another study, conducted at Walter Reed and the University of Pennsylvania, among participants who slept from two to nine hours daily for eight days, those who slept nine hours performed the best on "psychomotor vigilance" tasks, which measure reaction time.”

“There is a small group of people who don't need much sleep. We call them natural short sleepers. They can function perfectly well on just four to six hours of sleep each night, often for their entire lives. In 2010 researchers discovered genetic mutations that help explain this phenomenon. But here's the catch: most people who think they're natural short sleepers aren't. They're just chronically sleep-deprived.”

“Reducing sleep over time harms your brain function and overall health. There's no evidence that people can successfully adjust to getting less sleep. Adults need 7–9 hours of sleep. Reducing this harms health and performance.”

“Exercising has been shown to reduce insomnia and improve sleep quality. Exercising early in the day may be more beneficial than exercising at night for many people.”

“Consider the method put forth by Professor Jim Horne, a neuroscientist at Loughborough University. For the first week, delay your bedtime by 20 minutes. Delay bedtimes an additional 20 minutes each week until you’re sleeping six hours a night (most people struggle below six).”

“The American Academy of Sleep Medicine and Sleep Research Society consensus statement recommends that adults should sleep 7 or more hours per night on a regular basis to promote optimal health. Short sleep duration is associated with increased risk of weight gain, obesity, diabetes, hypertension, heart disease, stroke, depression, and impaired immune function.”