An adult needs from six to eight hours sleep, on an average. Mainly, the sleep duration is genetically determined. One is fresh, rested and fit for the day after five hours of sleep. The other one needs at least nine hours to feel perfectly slept off. But, more important than the sleep duration is the quality of sleep. And this also depends from being able to sleep through. It is normal to wake up up to 30 times per night – only when the waking phase lasts longer than three minutes our regeneration is suffering.
But simply sleeping more is not always advisable. There are studies which showed that not only a lack of sleep is harmful but on long-term also more than nine hours sleep per night.
Too much sleep can cause the following diseases and problems:
Depressive symptoms:
A study with grown up twins showed that a longer sleep duration increases the risk of depression. 27 % of the participants who slept from seven to nine hours showed depressive signs compared to 49 % of the participants who slept nine hours or more.
Weight gain:
In Canada, scientists observed in a long-term study that participants with a sleep duration of nine to ten hours per night rather gained five kilograms than those who slept from seven to eight hours – despite balanced nutrition and sufficient exercise. That means, the sleep duration has a significant influence on our weight.
More difficult pregnancy:
In Korea, the influence of the sleep duration on pregnancy of women with in-vitro fertilization was investigated. The sleep of 650 women was observed. These women were in hormone treatment because of a forthcoming in-vitro fertilization. The women who slept seven to eight hours showed the highest pregnancy-rate. The women who slept from nine to eleven hours showed the lowest. The scientists did not find a justified correlation of too much sleep and infertility. But it is proven that sleeping habits are influencing the menstrual cycle as well as hormone production.
Increased diabetes risk:
When sleeping too much, a decreased glucose tolerance might arise which might lead to diabetes.
Influence on the heart:
According to cardiologists, six to eight hours sleep protect from coronary diseases. When sleeping too less especially the risk for a strike as well as for a heart attack increases. But, long-sleeper are just as endangered like short-sleepers: the risks for coronary diseases and stroke are even higher.
Impairment of brain function:
Especially with elder women, an unhealthy amount of sleep may influence the brain function and lead to forgetfulness.
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