A recent study published in Neurobiology of Aging evaluated the association between common cerebrovascular and neurodegenerative pathologies and clinical hypothyroidism. The study analyzed the National Alzheimer’s Coordinating Center’s Uniform Data Set (UDS) data gathered from U.S. Alzheimer’s Disease Centers and utilized two separate samples. One sample included UDS participants who had been autopsied, while the second sample included UDS participants that were still alive or had died but had not been autopsied, which researchers referred to as the clinical sample. The study consisted of 2,837 autopsied participants and 26,930 clinical-sample patients.
Each Alzheimer’s Disease Center that participated conducted neuropathologic assessments according to center-specific protocols. Neuropathologists utilized a standardized form to classify patients as having Alzheimer’s disease neuropathologic change (ADNC), which included staging for amyloid-beta immune-reactive plaques. Additionally, the presence of cortical micro infarcts and/or gross infarcts was recorded. Investigators assessed for cerebral amyloid angiopathy, atherosclerosis, and arteriolosclerosis, as well as Lewy body disease. Statistical tests were done in order to evaluate whether these characteristics differed in distribution between those with and without treated hypothyroidism.
Researchers also examined associations between thyroid disease and vascular disease. In the autopsied sample, this included assessing for associations between vascular risk factors, cardiovascular disease, clinical cerebrovascular disease, and cerebrovascular pathologies. In the clinical sample, the association between vascular risk factors, cardiovascular disease, clinical cerebrovascular disease, and hypothyroidism were investigated in patients with or without dementia at baseline.
In the autopsied group, there were 555 participants with treated hypothyroidism and 2,146 without known thyroid disease. Additionally, there were 4,598 clinical participants with hypothyroidism and 20,045 without thyroid disease. Before controlling for confounding factors, researchers found that participants with thyroid disease were less likely to be demented and were less likely to have high ADNC or Lewy body disease. Additionally, gross infarcts and atherosclerosis were more common in the patients with hypothyroidism. Hypercholesterolemia, atrial fibrillation, and cerebrovascular disease were associated with hypothyroidism in subsamples.
Overall, investigators concluded that clinical hypothyroidism was associated with cardiovascular and cerebrovascular disease. These findings are consistent with the existing literature. On the other hand, the correlations between neurodegenerative diseases were weaker with no reported association between hypothyroidism and Alzheimer’s disease–type amyloid plaques or neurofibrillary tangles. While further studies are needed to determine a link between causes of dementia in patients with thyroid disease, the treatment of this endocrine-disease state in the elderly population remains an area of importance, as proven by the association with cardiovascular disease.
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