Coexisting Depression and Insomnia Significantly Raise Alzheimer’s and Dementia Risk, Large Study Finds

The research, led by SangNam Ahn from the Department of Health Management and Policy at Saint Louis University, in collaboration with Texas A&M University, analyzed the combined impact of these conditions to guide dementia prevention and intervention strategies.

Using data from the TriNetX electronic health records network, the retrospective cohort study included over 1.86 million dementia-free adults aged 50 and above, followed between 2011 and 2023. Of the participants, 58% were between 50 and 64 years old, 59% were female, and 82% identified as White.

The study led to the following findings:

• At baseline, 1.1% of participants had both insomnia and MDD.
• 3.8% of participants reported only insomnia.
• 4.8% had MDD alone.
• 90.4% had neither condition.
• The overall incidence of ADRD was 2.3%, equivalent to 28.8 cases per 10,000 person-years.
• Individuals with both insomnia and MDD had a 91% higher risk of developing ADRD compared to those without either condition (HR = 1.91).
• MDD alone increased the risk of dementia by 70%.
• Insomnia alone was linked to an 11% increase in dementia risk.
• The associations were consistent across racial groups, suggesting the findings apply broadly to different populations.

The study highlights the critical role of mental health in dementia prevention, highlighting that MDD appears to be the dominant factor driving risk, with insomnia acting as an additional amplifier when present concurrently. According to the authors, early detection and management of both sleep disturbances and depressive symptoms could be vital in lowering the burden of ADRD in aging populations.

The researchers advocate for routine screening for insomnia and depression among middle-aged and older adults as part of comprehensive dementia risk reduction strategies. They also call for integrated mental health care approaches that address both conditions simultaneously, potentially delaying or preventing the onset of neurodegenerative disorders. Future investigations are recommended to explore sex- and age-specific differences, evaluate the impact of changes in exposure over time, and assess potential pharmacological and behavioral interventions that could mitigate dementia risk linked to these mental health conditions.

"These findings add to the growing body of evidence emphasizing the intersection between mental health and cognitive decline. For policymakers and healthcare providers, the results highlight the importance of incorporating mental health assessment and treatment into dementia care frameworks," the authors wrote.

"By adopting proactive strategies to address insomnia and MDD early, it may be possible to reduce long-term dementia risk and improve quality of life for aging individuals worldwide," they concluded.

Reference:

Ahn, S., Salas, J., Cho, J., & Scherrer, J. F. (2025). Insomnia, major depressive disorders, and risk for Alzheimer’s disease and related dementias. Aging & Mental Health, 1–10. https://doi.org/10.1080/13607863.2025.2533495