Association of thyroid disease with risks of dementia and cognitive impairment: A meta-analysis and systematic review.

Introduction: It is still uncertain whether the risk of dementia and cognitive impairment is related to thyroid disease. we carried out a meta-analysis and systematic review (PROSPERO: CRD42021290105) on the associations between thyroid disease and the risks of dementia and cognitive impairment. Methods: We searched PubMed, Embase, and Cochrane Library for studies published up to August 2022. The overall relative risk (RRs) and its 95% confidence interval (CIs) were calculated in the random-effects models. Subgroup analyses and meta-regression were conducted to explore the potential source of heterogeneity among studies. We tested and corrected for publication bias by funnel plot-based methods. The Newcastle-Ottawa Scale (NOS) or Agency for Healthcare Research and Quality (AHRQ) scale were used to evaluate the study quality of longitudinal studies and cross-sectional studies, respectively. Results: A total of 15 studies were included in our meta-analysis. Our meta-analysis showed that hyperthyroidism (RR = 1.14, 95% CI = 1.09-1.19) and subclinical hyperthyroidism (RR = 1.56, 95% CI = 1.26-1.93) might be associated with an elevated risk for dementia, while hypothyroidism (RR = 0.93, 95% CI = 0.80-1.08) and subclinical hypothyroidism (RR = 0.84, 95% CI = 0.70-1.01) did not affect the risk. Discussion: Hyperthyroidism and subclinical hyperthyroidism are predictors of dementia. Systematic review registration: PROSPERO, Identifier: CRD42021290105.