Sleep is one of the activities needed to maintain health. But in fact, sleep duration should be limited to no more or less.

Sleeping less than 5 hours or more than 9 hours per day at risk of developing dementia or a decline in brain function that one character is senile in old age. 6-8 hours of sleep is considered as the ideal of human needs.

Recently a study found that regular naps and sleep at night for too long could be an early symptom of dementia or even contribute to brain disorders, especially if it is entering the elderly.

“These results suggest that the perceived sleepiness during the day could be the early symptoms of cognitive decline,” said Dr. Claudine Berr from the Institut National de la Sante et de la Recherche Medical (Inserm) in the Alzheimer’s Association International Conference in Vancouver.

In another study, also presented in Vancouver, a group of American researchers found that regularly sleep more than 9 hours a night or less than five hours may be associated with lower mental ability.

Devore and colleagues also found that participants who slept too much or too little of the chemical changes in the brain that indicate early symptoms of Alzheimer’s disease or the most common form of dementia.

“From time to time that extreme sleep duration may contribute to cognitive decline and early Alzheimer’s symptoms and not simply passive symptoms of both,” said Devore as reported by the Telegraph, Saturday (07/21/2012).