Thyroid Function and Depressive Symptoms in Older Adults: A Five-Year Follow-Up

Abstract

Background: Thyroid function and depressive disorders have a reciprocal correlation. Objectives: This study was performed to assess the association between thyroid function and depressive symptoms in older adults. Methods: In this cohort study, all older adults (aged 60 or over) recruited in the Amirkola Health and Ageing Cohort Project (AHAP) were followed from 2011 to 2016. At a baseline examination, depressive symptoms were assessed using the geriatric depression scale (GDS). Thyroid function was evaluated with the serum levels of T3, T4, and thyroid stimulating hormone (TSH). Older adults whose GDS scores showed no depressive symptoms at the baseline were followed for five years. The t-test, ANOVA, logistic regression model, and Pearson's correlation coefficient were used for data analysis. Results: Totally, 1,463 individuals completed the first phase of the study. We showed that 623 (45.3%) persons with a mean age of 69.6 ± 7.3 years had mild-to-severe depression and 840 (54.7%) individuals had no depressive symptoms. The baseline thyroid function of the participants showed that the mean levels of T3 (0.330), T4 (0.312), and TSH (0.064) had no significant difference between patients with depressive symptoms and individuals without these symptoms. After the baseline assessment, 571 individuals who did not have depressive symptoms were followed for five years. The results showed that 69 (12.1%) persons were hypothyroid and six (1.1%) were hyperthyroid. Overt or subclinical hypo (P = 0.103) or hyper (P = 0.128) thyroid function had no significant difference between older adults who were depressed and non-depressed. Conclusions: A five-year follow-up of elderly people revealed no significant correlation between depressive symptoms and thyroid function in this population.