People who sleep more than 9 hours a day experience cognitive decline much faster than those who only iron the hour for a period of 6 to 8 hours a day, according to a study just published in the Journal of Psychiatric Research . The research is based on an analysis carried out over 3 years with more than a thousand people who, adding the time of night rest and naps, slept at least 9 hours every day. Studying their evolution, the scientists observed that the cognitive deterioration in the sleepers was 0.2 points per year according to the Mini-Mental State Examination (MMSE) , a practical test that allows to establish the degree of cognitive state of the patient and thus be able to detect signs of dementia. In contrast, for those who slept the recommended hours (less than 8) the decline on the same scale was 0.0 points per year.
Although the cause-effect relationship is not yet clear, Julián Benito-León and his colleagues from the "12 de Octubre" University Hospital in Madrid, authors of the research, consider two options: that excessive sleep is an early sign of cognitive deterioration or that sleeping excessively damages the brain in some way.
