Those with the common thyroid disorder displayed a more than 80% increased risk of dementia, with a more than 3-fold increase in the risk among those requiring hormone replacement therapy.
A version of this article previously appeared on our sister site, Endocrinology Network.
New data from a large-scale case-control study of more than 15,000 patients in Taiwan suggest that older individuals with hypothyroidism have a greatly increased risk of developing dementia compared with those without the common thyroid disorder.1
Ultimately, this was conveyed as an 81% increased risk, with the results also demonstrating a more than 3-fold increase in the risk of dementia among patients requiring thyroid hormone replacement therapy. The study was conducted by senior investigator Chien-Hsiang Weng, MD, MPH, clinical assistant professor of family medicine, Brown University, and colleagues.
“In some cases, thyroid disorders have been associated with dementia symptoms that can be reversible with treatment,” Weng said in a statement.2 “While more studies are needed to confirm these findings, people should be aware of thyroid problems as a possible risk factor for dementia and therapies that could prevent or slow irreversible cognitive decline.”
The study included patients aged 65 years or older who had newly diagnosed dementia without a prior history of the condition or other neurodegenerative disease, identifying 15,686 patients for inclusion in the study. Weng et al wrote that 7843 adult patients did not have a dementia diagnosis prior to index date for the 2006 to 2013 period that was reviewed. These were then age- and sex-matched with 7843 patients from the cohort with newly diagnosed dementia. The mean age for the cohort of patients with dementia was 74.9 years (SD, 11.3) and the mean age for the patients without dementia was 74.5 years (SD, 11.3).1
In adjusted analyses, the data showed a significant association between a history of hypothyroidism and the risk of dementia among patients aged 65 years or older (aOR, 1.81; 95% CI, 1.14-2.87; P = .011). This increase, however, was not observed among those in the subgroup of individuals aged at least 50 years but younger than 65 years (aOR, 2.43; 95% CI, 0.83-7.12; P = .106).
When evaluating the risk of dementia based on a history of hyperthyroidism, there were no statistically significant associations observed for those aged at least 50 years but younger than 65 years (aOR, 0.67; 95% CI, 0.22-1.99; P = .465) and those aged 65 years or older (aOR, 1.33; 95% CI, 0.91-1.95; P = .139).
Further subgroup analysis in those older than 65 years with hypothyroidism suggested those receiving thyroid hormone replacement therapy (HRT) were at a more than 3-fold increase in the risk of dementia when compared their counterparts not receiving thyroid HRT (aOR, 3.17; 95% CI, 1.04-9.69; P=.043). There were no statistically significant differences observed among patients with hyperthyroidism who received treatment in the form of medication or surgery (aOR, 0.55; 95% CI, 0.23-1.31; P = .178), surgery or surgery and medication (aOR, 1.95; 95% CI 0.15-24.99; P = .609), and medication alone (aOR, 0.50; 95% CI, 0.21-1.21; P=.125) with risk of dementia.
Additionally, the investigators identified significant differences between the case and control groups in the risk of developing dementia among those with a history of hypertension (3712 [47.3%] vs 3211 [40.9%]; P <.001), diabetes (2145 [27.3%] vs 1394 [17.8%]; P <.001), coronary artery disease (1176 [15.0%] vs 1001 [12.8%]; P <.001), depression (159 [2.0%] vs 24 [0.3%]; P <.001), tinnitus (167 [2.1%] vs 125 [1.6%]; P = .013), and alcohol dependence (38 [0.5%] vs 2 [0.0%]; P <.001).
Citing a lack of literature on the association between thyroid disorders and dementia in Asian populations, Weng and colleagues designed the study with the intent of assessing the association of dementia with a diagnosis of hyperthyroid or hypothyroidism using the Taiwanese National Health Insurance Research Database. “We hope these findings will better inform physicians and patients alike of the risk factors of dementia and possible therapies to prevent or slow irreversible cognitive decline,” they wrote.