The correlation also mentioned whether or not people took sleeping pills and whether or not they had a mutation called ApoE4 that makes people more likely to develop Alzheimer’s, said Dr. Sabia.
“The study found a modest association, but I would say a somewhat important association of short sleep and the risk of dementia,” said Pamela Lutsey, an associate professor of epidemiology and community health at the University of Minnesota who was not involved in the research. “Short sleep is very common and because of this, even if it is modestly associated with the risk of dementia, it can be important socially. Short sleep is something we have control over, something you can change. ”
However, as with other research in this area, the study had limitations that prevented it from demonstrating that inadequate sleep can help cause dementia. Most sleep data were self-reported, a subjective measure that is not always accurate, experts said.
At one point, nearly 4,000 participants had their sleep duration measured by accelerometers and that the data were consistent with their self-reported sleep time, the researchers said. However, that quantitative measure came late in the study, when participants were about 69 years old, making it less useful than if it had been obtained at younger ages.
In addition, most participants were white and better educated and healthier than the general British population. And, based on electronic medical records to diagnose dementia, researchers could have missed some cases. They also could not identify the exact types of dementia.
“It’s always hard to know what to draw from these types of studies,” wrote Robert Howard, a professor of psychiatry for the elderly at University College London, one of several experts who sent comments on the study to Nature Communications. “Insomniacs – who probably don’t need anything else to chew in bed,” he added, “shouldn’t worry about heading for dementia unless they sleep right away.”
There are compelling scientific theories as to why too little sleep could exacerbate the risk of dementia, especially Alzheimer’s. Studies have found that the levels of cerebrospinal fluid in amyloid, a protein that clumps together in Alzheimer’s plaque, “increase if you look at sleep people,” said Dr. Musiek. Other studies on amyloid and another Alzheimer’s protein, tau, suggest that “sleep is important for removing protein from the brain or limiting production,” he said.