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Meta-Analysis
. 2024 Sep;14(9):e70037.
doi: 10.1002/brb3.70037.

Subclinical hyperthyroidism and the risk of dementia: A meta-analysis

Qiao Liu  1 , Chaoyin Lu  1 , Mengdie Chen  1 , Ping Feng  1
Affiliations
Meta-Analysis

Subclinical hyperthyroidism and the risk of dementia: A meta-analysis

Qiao Liu et al. Brain Behav. 2024 Sep.

Abstract

Background: Accumulating evidence suggests that thyroid dysfunction may be related to the risk of dementia. However, previous studies evaluating the association between subclinical hyperthyroidism and the risk of dementia showed inconsistent results. This systematic review and meta-analysis were performed to evaluate the relationship between subclinical hyperthyroidism and the incidence of dementia in the general population.

Methods: Cohort studies relevant were retrieved by searching the electronic databases including PubMed, Web of Science, and Embase. A random-effects model was used to combine the data by incorporating the influence of between-study heterogeneity. Subgroup and meta-regression analyses were performed to investigate the source of heterogeneity.

Results: Nine cohort studies including 49,218 community-derived participants were included. Among them, 3177 (6.5%) had subclinical hyperthyroidism at baseline. During a mean follow-up of 10.2 years, 4044 participants developed dementia. The pooled results showed that compared to the participants with euthyroidism, those with subclinical hyperthyroidism had a higher incidence of dementia (risk ratio: 1.38, 95% confidence interval: 1.09 to 1.74, p = .006; I2 = 47%). Subgroup analyses according to study design, age of the participants, methods for diagnosis of dementia, or analytic model did not significantly change the results. The univariate meta-regression showed that the cutoff of thyroid-stimulating hormone for defining subclinical hyperthyroidism negatively affected the association between subclinical hyperthyroidism and dementia (coefficient: -1.44, p = .009), which completely explained the heterogeneity (residual I2 = 0%).

Conclusion: Subjects with subclinical hyperthyroidism may have a higher risk of dementia compared to those with euthyroidism.

Keywords: dementia; meta‐analysis; risk factor; subclinical hyperthyroidism; thyroid function.

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Conflict of interest statement

The authors declare that they have no conflict of interest.

Figures

FIGURE 1
FIGURE 1
Process of literature search and study identification.
FIGURE 2
FIGURE 2
Forest plots for the meta‐analysis of the association between subclinical hyperthyroidism and dementia: (A) forest plots for the meta‐analysis of the outcome of overall dementia and (B) forest plots for the meta‐analysis of the outcome of AD.
FIGURE 3
FIGURE 3
Forest plots for the subgroup analyses of the association between subclinical hyperthyroidism and the risk of overall dementia: (A) subgroup analysis according to study design and (B) subgroup analysis according to age group of the participants.
FIGURE 4
FIGURE 4
Forest plots for the subgroup analyses of the association between subclinical hyperthyroidism and the risk of overall dementia: (A) subgroup analysis according to the methods for the diagnosis of dementia and (B) subgroup analysis according to the regression model used for the analyses.
FIGURE 5
FIGURE 5
Univariate analysis to evaluate the influence of TSH cutoff used for the diagnosis of subclinical hyperthyroidism on the association between subclinical hyperthyroidism and risk of dementia.
FIGURE 6
FIGURE 6
Funnel plots for the publication bias underlying the meta‐analysis of the association between subclinical hyperthyroidism and overall dementia.
See this image and copyright information in PMC

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