Overview

• Researchers followed 2,750 cognitively healthy adults with an average age of 70 for about 5.6 years, with 16% meeting the study’s definition of chronic insomnia.
• People with chronic insomnia had a 40% higher chance of developing mild cognitive impairment or dementia after adjustments for key health factors, a difference comparable to about 3.5 years of aging.
• Participants with insomnia showed more amyloid plaques and greater white matter hyperintensities on imaging, pointing to both Alzheimer‑type and small‑vessel pathways.
• Those who reported sleeping less than usual started with lower cognitive scores and more brain changes, and carriers of the APOE ε4 gene experienced steeper declines.
• Authors stressed the results show association rather than causation, noted limits of medical‑record diagnoses, and called for randomized trials; the study was supported by NIH, foundations, and a Sleep Number grant to Mayo Clinic.