Hypothyroidism a risk factor for dementia

Patients with hypothyroidism are at increased risk of developing dementia, with the association modified by comorbidity and age, as reported in a study.

The analysis comprised two cohorts: the DNPR, which included 111,565 hypothyroid patients (diagnosed between 1995 and 2012) and 446,260 euthyroid age‐ and sex‐matched individuals; and the OPENTHYRO, which comprised 233,844 individuals with at least one measurement of serum thyrotropin (TSH) between 1995 and 2011, of whom 2,894 had hypothyroidism. The median follow-up time was 6.2 and 7.2 years in the respective cohorts.

Cox analysis showed that in the DNPR cohort, hypothyroidism contributed to a heightened risk of dementia (hazard ratio [HR], 1.22, 95 percent confidence interval [CI], 1.17–1.27). This association was attenuated after adjusting for pre‐existing comorbidity (HR, 0.82, 95 percent CI, 0.79–0.86).

Meanwhile, stratification of age into ≤56 and >56 years revealed an inverse relationship between age and risk of dementia among patients with hypothyroidism (≤56 years: HR, 2.03, 95 percent CI, 1.62–2.53; >56 years, HR, 1.00, 95 percent CI, 0.96–1.05).

In the OPENTHYRO cohort, dementia risk increased by 12 percent for each 6 months of elevated TSH (HR, 1.12, 95 percent CI, 1.07–1.16). This indicated that the duration of hypothyroidism could also influence the risk of dementia.