The study, conducted by scientists at the UK’s Imperial College London, analyzed the relationship between various sleep patterns, major depressive disorder symptoms and Alzheimer’s disease by evaluating genome-wide association studies, which are studies that link various diseases to genes.
"We know that people with Alzheimer's disease often report depression and various sleep problems, like insomnia," study author Abbas Dehghan of Imperial College London said in an August 19 news release.
"We wanted to find out if there are causal relationships between different sleep patterns and depression and Alzheimer's,” he added.
The scientists looked at data compiled from the International Genomics of Alzheimer’s Project, which involves about 64,000 people, as well as the Psychiatric Genomics Consortium, involving around 19,000 people.
Data from the UK Biobank, which compiles the health and genetic information of around half a million people, was also collected. By analyzing the databases, the researchers concluded that disturbed sleep patterns are linked to Alzheimer’s disease.
Specifically, the researchers found that people with twice the genetic risk for Alzheimer’s disease were 1% more likely to refer to themselves as “morning people” compared to people with lower genetic risks. In addition, people with twice the genetic risk of Alzheimer’s had a 1% lower risk of insomnia.
The researchers did warn that the study only shows a possible association between sleep patterns and Alzheimer’s, rather than a direct chain of cause and effect. There was also no causal link found between major depressive disorder and Alzheimer’s.
Another limitation of the study was that most of the subjects whose data was used were of European ancestry. The same results may therefore not apply to people of different ethnicities.