OBJECTIVE: There is limited data concerning the effect of untreated subclinical thyroid disorders on mortality in older adults. Therefore, this study aimed to analyze 5-year overall mortality among participants in the PolSenior study with treated and untreated subclinical thyroid dysfunction. DESIGN AND METHODS: The study group consisted of 407 participants with thyroid disorders (305 with hypothyroidism and 102 with hyperthyroidism) and 2776 euthyroid individuals aged 65 years and older. Overall mortality risk factors were assessed with Cox proportional hazard regression. Additionally, overall survival analyses were performed with Kaplan‒Meier estimates stratified by sex and hypo-/hyperthyroidism status. RESULTS: In women, there was no difference in survival between the euthyroid and hypothyroid groups. Survival was significantly worse in patients with subclinical hyperthyroidism than in euthyroid and treated hyperthyroidism patients. In men, there were no differences in survival between the hyperthyroidism group and the subclinical hypothyroidism or euthyroid group. Notably, survival was better in the treated hypothyroidism group than in the euthyroid group. According to the multivariate models, subclinical hyperthyroidism appeared to be linked to a 30% reduction in survival among women (hazard ratio [HR] for mortality = 1.43
95% CI = 0.98-2.07, p = 0.06) but not among men. CONCLUSIONS: Our study showed that women with subclinical hyperthyroidism had a higher mortality rate. At the same time, men with treated hypothyroidism had improved survival compared to those in the euthyroid group among participants aged 65 years and older during a 5-year follow-up period. Subclinical hypothyroidism did not influence the survival rates.