Study author Dr. Diego Carvalho of the Mayo Clinic in Rochester, Minnesota, and a member of the American Academy of Neurology, wrote that the effects of insomnia are not just immediate in the morning after you awake; it likely impacts your brain health over time.
Driving the point home, Carvalho said, "sleep isn't just about rest -- it's also about brain resilience."
For nearly six years, Carvalho followed 2,750 cognitively healthy adult participants with an average age of 70. In that group, approximately 16 percent had chronic insomnia.
Initially, researchers asked the test subjects about their sleeping habits over the prior two weeks.
Along with that, memory and thinking tests were conducted, and brain scans were performed. More white matter hyperintensities -- areas where small-vessel disease may have damaged brain tissue -- and amyloid plaques, a protein that can build up and is linked to Alzheimer's disease, were detected.
Over the course of the study, 14 percent of the test subjects who reported chronic insomnia developed mild cognitive impairment or dementia, as compared to 10 percent who did not have insomnia.
The study also took into account varying factors, ranging from high blood pressure and age to use of sleeping pills and whether or not the subject had sleep apnea.
The Mayo Clinic study found that 40 percent of people were likely to develop mild cognitive impairment or dementia than those not experiencing insomnia.
They also had faster declines in tests measuring different thinking skills.
Among those with insomnia, researchers determined the type: those getting less sleep than usual in the past two weeks, or those getting more sleep than usual in the past two weeks.
People who reported getting less sleep than usual were more likely to have lower cognitive test scores at the beginning of the study, comparable to being four years older.
They also had more white matter hyperintensities and amyloid plaques. For amyloid, the effect was similar to what is seen in people with the APOE ε4 gene, a known genetic risk factor.
People who reported getting more sleep than usual, on the other hand, were more likely to have fewer white matter hyperintensities at the start of the study.