Chronic insomnia was associated with faster cognitive decline and a 40% higher risk of developing cognitive impairment, according to a longitudinal study from the Mayo Clinic Study of Aging (MCSA).
The study, led by Diego Z. Carvalho, MD, of Mayo Clinic, and colleagues, followed 2,750 cognitively unimpaired patients aged 50 years and older for a median of nearly 6 years. Patients with chronic insomnia experienced steeper declines in global cognitive scores and a higher risk of developing mild cognitive impairment or dementia compared with those without insomnia.
The link was strongest among patients who also reported reduced sleep duration. This subgroup performed worse on baseline cognitive testing—equivalent to being about four years older—and showed higher levels of white matter changes and amyloid burden on brain imaging. Their baseline amyloid burden was comparable to that seen in carriers of the APOE ε4 gene, a known risk factor for Alzheimer disease. In contrast, patients with insomnia who reported sleeping more than usual had lower baseline white matter changes, which researchers suggested may reflect symptom remission.
The study controlled for multiple confounders, including obstructive sleep apnea, depression, cardiovascular conditions, and APOE genotype. Use of sleep medications was not linked to differences in cognition or risk of impairment.
Patients underwent annual neuropsychological assessments covering memory, executive function, language, and visuospatial skills. Imaging included serial brain MRI and amyloid-PET scans. Differences in brain imaging measures were present at baseline but did not progress more rapidly among patients with insomnia.
The average age of participants was 70 years, and about half were women. Patients with chronic insomnia were more likely to be women and had higher rates of obstructive sleep apnea and depression than those without insomnia.
These findings build on earlier research showing that insomnia may increase dementia risk. The MCSA analysis extends prior work by highlighting the clinical importance of perceived sleep duration, even without objective confirmation.
Limitations include the largely White study population, lack of objective sleep measurements, and the long interval between initial insomnia diagnosis and assessment of sleep duration.
The research was supported by multiple National Institutes of Health grants as well as the GHR Foundation and Mayo Foundation for Medical Education and Research.
Disclosures can be found in the study.
Source: Neurology