By John Salak –
By now everyone should know a good night’s sleep is essential to physical and mental wellbeing—whether that person is a newborn, senior citizen or something in the middle. What’s less apparent is what exactly defines a good night’s sleep.
Further complicating the quest for defining a great snooze is that optimal sleep times differ by age. In fact, the older the individual, the less sleep they apparently need.
The Sleep Foundation, for example, reports that newborns require 14 to 17 hours of sleep daily. A preschooler should get 10 to 13 hours, while a teenager needs to nod off about 8 to 10 hours a day. By the time someone hits middle age, they should log 7 to 9 hours and when they hit 65 years old they probably don’t need more than 7 or 8 of sleep.
This all seems simple enough. At least people have an age-related target for nodding out. Unfortunately, a team of researchers from Washington University in St. Louis just threw a monkey wrench of sorts in this equation. They warned that people not only damage themselves if they sleep too little, they can also face serious consequences if they sleep too much, especially later in life.
The St Louis team reported that individuals who sleep in moderation gain optimal benefits. Too much or too little may generate cognitive decline. 
The scientists stepped into the research challenge noting that poor sleep and Alzheimer’s disease are linked to cognitive decline, which made identifying the effect of each challenging. They developed their findings by tracking cognitive function in older adults over several years and analyzing it against levels of Alzheimer’s-related proteins and measures of brain activity during sleep.
“It’s been challenging to determine how sleep and different stages of Alzheimer’s disease are related,” acknowledged Dr. Brendan Lucey, the report’s first author. But he stressed it is essential in the battle against various forms of cognitive decline.
“Our study suggests that there is a middle range, or ‘sweet spot,’ for total sleep time where cognitive performance was stable over time. Short and long sleep times were associated with worse cognitive performance, perhaps due to insufficient sleep or poor sleep quality,” he explained. “An unanswered question is if we can intervene to improve sleep, such as increasing sleep time for short sleepers by an hour or so, would that have a positive effect on their cognitive performance, so they no longer decline?”
The findings and associations identified by the research team are critical because Alzheimer’s is the main cause of a cognitive decline in older adults. In fact, its connected to approximately 70 percent of dementia cases. The essential connection to Lucey’s research is that low-quality sleep is not only a common symptom of the disease, it can also accelerate the disease’s progression.
“It was particularly interesting to see that not only those with short amounts of sleep but also those with long amounts of sleep had more cognitive decline,” said co-senior author David Holtzman, MD, a professor of neurology. “It suggests that sleep quality may be key, as opposed to simply total sleep.”
Lucey stressed that each person’s sleep needs are unique, so a standard number of age-related sleep hours doesn’t necessarily apply to everyone. What’s critical, however, is that individuals of any age feel they are well-rested. If not, they need to find ways to improve their sleeping patterns for they hit their snoozing sweet spot.
The long-term impact of poor sleep isn’t limited to mature adults. The University of Houston revealed that inadequate sleep in children has an immediate detrimental impact on their emotional functioning that may lead to long-term social problems.
The university’s team arrived at its findings after examining the changes in children’s emotional facial expressions after restricted sleep.
“Sleep problems in children are routinely linked with lower social competence and more problems in peer relationships, but we really don’t understand what drives these associations,” Professor Candice Alfano announced in releasing the study.
The Houston research team tested its theory by working with children ages 7 to 11 and assessing the emotional reactions after they were well-rested and then after they had two nights of partial sleep restrictions. The social functioning of the participants was also examined at the time and then two years later.
“As we suspected, children who displayed less positive facial expressions in response to pleasant images when sleep-restricted were reported to have more social problems two years later, even when controlling for earlier social problems,” said Alfano.
The university results support a growing body of evidence on the long-term socio-emotional impact poor sleep has on children, the report suggested.
