Thyroid dysfunction at baseline and incident depression after the four-year- follow-up of the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil)

Author(s)

Ana Carolina de Moraes Fontes Varella

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Faculdade de Medicina (FM/SBD)
• Defense date: 2020-08-20

Examining board members

Paulo Andrade Lotufo; Jose Leopoldo Ferreira Antunes; Danielle Bivanco de Lima; Claudia Kimie Suemoto

• Advisor: Paulo Andrade Lotufo

Abstract

Thyroid disorders have been associated with depression over many years, but the mechanisms involved in this association are difficult to define and previous published data are still conflicting. The majority of studies were performed in Europe and the United States, with a recent increase in Asia, and it is unknown if their results would replicate in the Brazilian population. Therefore, ELSA-Brasil presents the opportunity to study the association between thyroid dysfunction and depression in the Brazilian population and prospectively. Methods: TSH, free-thyroxine (FT4) and anti-TPO antibodies levels were evaluated at baseline. Depression diagnoses were performed using the Clinical Interview Schedule - Revised (CIS-R) at baseline and after the 4-year-follow-up. The following analysis were performed using Poisson regression models (95% confidence interval, CI95%): (1) association between thyroid dysfunction (overt and subclinical) and incident depression; (2) association between anti-TPO antibodies and incident depression; (3) association between anti-TPO antibodies together with only overt/subclinical hypothyroidism and incident depression; (4) TSH levels (3º quintile as reference) and incident depression among those with subclinical thyroid dysfunction and euthyroid individuals; (5) TSH levels (3º quintile as reference) and incident depression among euthyroid individuals; (6) TSH levels (1º quintile as reference) and incident depression among those with subclinical thyroid dysfunction and euthyroid individuals; (7) TSH levels (1º quintile as reference) and incident depression among euthyroid individuals; (8) TSH levels as a sensibility analysis. The analyses were stratified by sex when appropriate, and the multivariable model was adjusted for age, sex, race, education, body mass index (BMI), smoking, alcohol consumption, use of antidepressants/benzodiazepines and comorbidities. Results: This study showed an inverse association between overt hypothyroidism and incident depression (RR=0.54; 95% CI 0.35-0.84), but no association was found for subclinical hypothyroidism, overt and subclinical hyperthyroidism. Also, there was no association between presence of anti-TPO antibodies and incident depression (even when analyzing it together with overt and/or subclinical hypothyroidism only). Regarding TSH levels, among those with subclinical thyroid dysfunction and euthyroid individuals, low TSH levels were associated with an increased risk of depression, for all participants (RR=1.36; 95% CI 1.02-1.81) and for women (RR=1.64; 95% CI 1.15-2.33). Even within the normal range, for all (RR=1.46; 95% CI 1.08-1.99) and for women (RR=1.63; 95% CI 1.12-2.38). High TSH levels were associated with a lower risk of depression, also for all participants (RR=0.71; 95% CI 0.53-0.96) and for women (RR=0.67; 95% CI 0.47-0.95). The sensibility Conclusion: Overt hypothyroidism was associated with a lower risk of depression after 4 years of follow-up. The higher risk seems to be associated with low TSH levels among those with subclinical thyroid dysfunction and euthyorid individuals, even within the normal range. Specially among women. High TSH levels were associated with lower risk of depression, also for women. No association between TSH levels and incident depression was found among men (AU)

• FAPESP's process: 16/21937-9 - Overt, subclinical thyroid dysfunction and thyroid peroxidase antibody and their association with psychiatric disorders at baseline and after 4 years of follow-up of the Brazilian Longitudinal Study of Adult Health (ELSA-Brazil)
• Grantee: Ana Carolina de Moraes Fontes Varella
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)