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Using Retinal Imaging to Study Dementia
Published on: November 6, 2017
Thyroid function, the risk of dementia and neuropathologic changes: the Honolulu-Asia aging study
Frank Jan de Jong1, Kamal Masaki, Hepei Chen
1Department of Epidemiology & Biostatistics, Erasmus Medical Center, P.O. Box 2040, 3000 CA Rotterdam, The Netherlands. f.j.dejong@erasmusmc.nl
Neurobiology of Aging
|September 18, 2007
Summary
Higher thyroxine levels, not thyrotropin, were linked to increased dementia and Alzheimer's disease risk in older men. This association was also observed with Alzheimer's neuropathology in autopsy samples.
Area of Science:
- Neuroscience
- Endocrinology
- Gerontology
Background:
- Thyroid dysfunction is a known risk factor for cognitive impairment and dementia, including Alzheimer's disease (AD).
- The precise relationship between thyroid function and the development or progression of Alzheimer's pathology remains unclear.
Purpose of the Study:
- To investigate the association between thyroid function (thyrotropin, total thyroxine, free thyroxine) and the risk of dementia, specifically AD.
- To examine the relationship between thyroid function and Alzheimer-type neuropathology (neuritic plaques, neurofibrillary tangles) in a cohort of Japanese-American men.
Main Methods:
- Prospective population-based cohort study of 665 dementia-free Japanese-American men (aged 71-93 years) with available thyroid function data.
- Follow-up for dementia diagnosis over a mean of 4.7 years, with 106 developing dementia (74 with AD).
- Autopsy sub-study of 143 men to assess neuropathological markers of AD in relation to thyroid hormone levels.
Main Results:
- Higher levels of total and free thyroxine were associated with an increased risk of developing dementia and AD.
- Specifically, a standard deviation increase in free thyroxine correlated with a 1.21 hazard ratio for dementia and 1.31 for AD.
- In autopsied brains, higher total thyroxine levels were linked to a greater number of neocortical neuritic plaques and neurofibrillary tangles. No association was found for thyrotropin.
Conclusions:
- Elevated thyroxine levels are associated with both the clinical diagnosis of Alzheimer's disease and its underlying neuropathology.
- Thyroid hormone levels, particularly thyroxine, may play a role in the pathogenesis or progression of Alzheimer's disease.
- Further research is warranted to elucidate the mechanisms linking higher thyroxine levels to Alzheimer's disease.
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