Depression, insomnia, hypertension, and type 2 diabetes can appear years before the onset of Alzheimer’s disease, according to researchers at Vanderbilt University Medical Center. The findings were published in Alzheimer’s Research & Therapy (ART).

Alzheimer’s disease is a neurodegenerative condition that develops gradually over decades. The researchers sought to identify medical conditions that commonly occur long before the characteristic memory impairments and cognitive decline appear.

The team analyzed de-identified electronic health records from millions of patients in two large U.S. databases. The main sample compared over 43,000 people with Alzheimer’s to more than 400,000 without the diagnosis. They examined patients’ medical histories during the ten years prior to dementia onset and compared them with the control group.

Key findings:

  • Individuals who later developed Alzheimer’s were more likely to have psychiatric disorders, particularly depression, as well as severe neuropsychiatric symptoms.

  • Sleep disturbances, including insomnia and sleep apnea, were also more common.

  • Risk for cognitive decline was higher in people with type 2 diabetes and cardiovascular conditions such as hypertension and ischemic cerebrovascular disease.

Additional analysis using DNA biobank data showed that some of these conditions are also linked to genetic risk factors for Alzheimer’s. The authors emphasize that these associations do not prove direct causation, but they help identify higher-risk populations more accurately.

Researchers note that earlier detection and management of these conditions could be an important preventive strategy. Even delaying the onset of Alzheimer’s by five years could significantly reduce the overall prevalence of the disease.