A groundbreaking review of over 200 studies reveals that approximately one-third of all dementia cases worldwide—nearly 19 million people—may be connected to diseases originating outside the central nervous system. This finding challenges traditional neurological views of dementia and highlights the critical interplay between peripheral health and cognitive decline.
The Emerging Picture of Dementia’s Roots
For decades, dementia has been primarily studied as a brain-centric disease. However, recent research increasingly demonstrates that conditions affecting other organs can significantly increase dementia risk. The new systematic review, conducted by scientists at Sun Yat-sen University in China, identifies 16 peripheral diseases strongly correlated with cognitive impairment.
The top five culprits are:
- Gum disease (periodontitis)
- Chronic liver diseases
- Hearing loss
- Vision loss
- Type 2 diabetes
Other linked conditions include osteoarthritis, kidney disease, cardiovascular disease, COPD, and inflammatory disorders like multiple sclerosis. While the review does not prove direct causation, the strong correlations suggest that preventing or managing these peripheral diseases could lower dementia incidence.
Why This Matters: Beyond the “Brain-Centric” View
The connection between peripheral health and dementia is not coincidental. The brain, though often viewed as isolated, is deeply interconnected with the rest of the body via the brain-gut axis, brain-bone axis, brain-immune axis, and more. These pathways allow systemic inflammation, metabolic dysfunction, and other processes to impact brain health directly.
“Overall, these insights illustrate the multidimensional burden of dementia related to a wide range of peripheral diseases at the population level,” write the review authors, “highlighting the potential role of peripheral organ function in brain health and the possibility to target those influential peripheral diseases to mitigate the growing dementia burden.”
This realization is crucial because many clinical trials for dementia drugs have failed by focusing solely on brain-based interventions. The assumption that cognitive decline begins and ends in the brain may have led researchers to overlook key targets.
The Shift in Perspective: From Neurological to Systemic
Emerging theories now position dementia not just as a neurological disorder but as a systemic one, potentially rooted in immunological or metabolic dysfunction. For example, some scientists, like Donald Weaver at the University of Toronto, suggest that Alzheimer’s may be an immunological disorder at its core, affecting the entire body. Others point to faulty energy production within cells as a root cause of widespread cognitive problems.
The review also found that conditions like hypertension, obesity, high cholesterol, depression, and thyroid disease had weaker or no significant link to dementia risk. This suggests the connection is specific to certain systemic conditions rather than overall poor health.
Ultimately, the growing body of evidence underscores that the brain isn’t an island. To effectively combat dementia, researchers must broaden their scope and address peripheral health alongside neurological factors. This shift in perspective holds the potential to unlock more effective prevention strategies and treatments.
