Optimal sleep duration
Too little, too much: Why it is so important to find the “sweet spot” when sleeping
Persistently poor sleep can damage the substance.
© Tero Vesalainen / Getty Images
Everyone needs sleep. The only question is how much. Researchers have calculated how many hours of sleep are optimal – and those who sleep a lot will be amazed.
While some get by with just a few hours of rest at night, jump through life fit as a sneaker, others cannot sleep as much as they are tired. You simply do not recover. Good sleep is important for the body. Anyone who cannot find rest at night for a long period of time breaks down, also mentally. But – and this is the crux of the matter – more sleep alone is not the solution. On the contrary.
Neurologists and sleep researchers from the USA have investigated the relationship between sleep and cognitive abilities. To do this, they collected data for more than four years. 100 people, an average of 75 years old, took part in the study by the Washington University of Medicine. The results have now been published in the specialist magazine “Brain”.
Sleep? Moderate, please
It is well known how important periods of recovery through sleep are for the body. Poor sleep, on the other hand, is associated with a decline in mental abilities. The same applies to Alzheimer’s disease. Bad sleep is a common symptom of the condition.
In order to understand possible connections between sleep, mental abilities and Alzheimer’s, the participants were examined regularly. This included tests in which various cognitive skills were tested and compared with the hours of sleep. The researchers also looked for signs of Alzheimer’s disease in the blood and spinal fluid. In addition to the subjective sleep assessment, the duration of sleep was also measured objectively using the EEG, for which the participants spent four to six nights in the sleep laboratory.
In most of the study participants, the scientists were unable to determine any cognitive impairments; only eleven test subjects had very slight impairments and one had slight impairments. However, the researchers found a U-shaped relationship between sleep and mental degradation. Accordingly, the values worsened when the subjects slept particularly short or long.
Find your personal “sweet spot”
“It was particularly interesting to see that not only those who had too little sleep, but also those who slept late, had more severe cognitive decline,” reports David Holtzman, neurologist and co-author of the study. This suggests that the quality of sleep is crucial, and not just the total length of sleep. It is important to find the personal “sweet spot”, i.e. the amount of sleep that is good for the individual.
Put simply, a “sweet spot” is a type of zone that is particularly effective. In tennis, it means the area of the racket from which the ball can be hit perfectly – i.e. particularly precisely, particularly quickly. The researchers also want to find such a spot in sleep, at least in older people. “Our study suggests that there is a mid-range, or ‘sweet spot’, of total sleep time where cognitive performance has been stable over time,” said sleep researcher Brendan Lucey, who led the study. Accordingly, this is in the range of five and a half and seven and a half hours of sleep.
The researchers’ results suggest that those who orientate themselves on this “sweet spot” stay fresh in the head longer. But could improved sleep also stop the progression of Alzheimer’s disease and thus the decline in cognitive abilities? It is difficult to see a connection between sleep and the various stages of Alzheimer’s disease. More data is needed to answer that question, Lucey said.
Everyone needs a different amount of sleep. If this is relaxing, although the number of hours is not in the time frame calculated by the scientists, that does not mean that some suddenly have to sleep more and others less. However, improvements should be made if there are sleep disorders or many hours of sleep do not bring recovery.
“Patients often report that they do not sleep well. When their sleep problems are treated, their cognitive abilities often improve too,” said Beau M. Ances, co-author of the study. He treats patients with dementia and other neurodegenerative diseases at Barnes-Jewish Hospital. He says, “Doctors should ask patients with cognitive complaints about the quality of their sleep. This is a potentially changeable factor.”
Source: Washington University School, Brain