Too Much Sleep Linked To Dementia, New Study Finds

A new study has found that people who sleep too much, around nine hours or more a night, are at higher risk for developing dementia, reported The Daily Mail.

Dementia is a broad term used to describe various progressive neurological disorders, with Alzheimer's being the most common disease affecting the brain. Early markers of dementia include a decline in memory and language skills.

Researchers from the University of Miami Miller School looked at 5,247 Hispanic participants, all aged between 45 and 75, over the course of seven years. Participants were all part of the nationwide Hispanic Community Health Study/Study of Latinos and were from cities including Chicago, Miami, San Diego, and the Bronx in New York City.

Participants in the study were given a neurocognitive test at the start and at the end of the study to test attention, memory, language, reaction time, and perception. They were also asked to fill out questionnaires about their sleep habits and the number of hours they slept per night over the course of a week. Included in the questionnaire were questions about what time they went to bed and woke up and if they had taken any naps during the day.

Social worker Nuria Casulleres shows a portrait of Prince Charles, Prince of Wales to an elderly woman during a memory activity at the Cuidem La Memoria elderly home, which specializes in Alzheimer patients on August 2, 2012 in Barcelona, Spain.
Getty Images | David Ramos

Scientists followed the participants for seven years and saw cognitive performance decrease for those who slept more than nine hours per night -- around 15 percent of participants. Within these 15 percent, learning skills plummeted by 22 percent, word fluency decreased by 20 percent, and memory dropped by 13 percent.

Too much sleep has been linked to an increase in white matter hyperintensities, or brain lesions that are believed to be caused by a decrease of blood flow to the brain and raise the risk of cognitive decline, dementia, and stroke.

Dr. Ramos, a neurologist and sleep expert at the University of Miami, commented on the study's findings.

"Insomnia, and prolonged sleep duration appear to be linked to a decline in neurocognitive functioning that can precede the onset of Alzheimer's disease or other dementias. We observed that prolonged periods of sleep and chronic insomnia symptoms led to declines in memory, executive function and processing speed."
The doctor added that these measures can precede the development of mild cognitive impairment and Alzheimer's disease. He hopes that the results can help doctors identify at-risk patients who may benefit from early intervention to prevent or reduce the risk of dementia while showing how too much sleep, especially in Hispanic patients who are at a higher risk of developing Alzheimer's, can lead to the disease.