Abstract
BackgroundMetabolic factors are increasingly recognized to play an important role in the pathogenesis of Alzheimer’s disease and dementia. Abnormal parathyroid hormone (PTH) levels play a role in neuronal calcium dysregulation, hypoperfusion and disrupted neuronal signaling. Some studies support a significant link between PTH levels and dementia whereas others do not.MethodsWe conducted a systematic review through January 2014 to evaluate the association between PTH and parathyroid conditions, cognitive function and dementia. Eleven electronic databases and citation indexes were searched including Medline, Embase and the Cochrane Library. Hand searches of selected journals, reference lists of primary studies and reviews were also conducted along with websites of key organizations. Two reviewers independently screened titles and abstracts of identified studies. Data extraction and study quality were performed by one and checked by a second reviewer using predefined criteria. A narrative synthesis was performed due to the heterogeneity of included studies.ResultsThe twenty-seven studies identified were of low and moderate quality, and challenging to synthesize due to inadequate reporting. Findings from six observational studies were mixed but suggest a link between higher serum PTH levels and increased odds of poor cognition or dementia. Two case-control studies of hypoparathyroidism provide limited evidence for a link with poorer cognitive function. Thirteen pre-post surgery studies for primary hyperparathyroidism show mixed evidence for improvements in memory though limited agreement in other cognitive domains. There was some degree of cognitive impairment and improvement postoperatively in observational studies of secondary hyperparathyroidism but no evident pattern of associations with specific cognitive domains.ConclusionsMixed evidence offers weak support for a link between PTH, cognition and dementia due to the paucity of high quality research in this area.
Highlights
In the absence of disease modifying or curative treatments, the identification of potentially modifiable risk factors for Alzheimer’s disease and other dementia subtypes is important
We conducted a systematic review through January 2014 to evaluate the association between Parathyroid hormone (PTH) and parathyroid conditions, cognitive function and dementia
There was some degree of cognitive impairment and improvement postoperatively in observational studies of secondary hyperparathyroidism but no evident pattern of associations with specific cognitive domains
Summary
In the absence of disease modifying or curative treatments, the identification of potentially modifiable risk factors for Alzheimer’s disease and other dementia subtypes is important. Hyperparathyroidism, characterized by elevated/high PTH levels, has been associated with many chronic conditions including impaired cognitive function and dementia [8,9,10,11]. Patients with primary hyperparathyroidism (high PTH and calcium levels), the most common parathyroid disease, often report cognitive complaints and observational studies have described poorer cognitive function in those patients compared to control groups including impaired performance in memory and attention tasks [12, 13]. Our aim was to conduct a systematic review to update and evaluate the current research for the association of PTH and parathyroid conditions with cognitive function and dementia. Some studies support a significant link between PTH levels and dementia whereas others do not.
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