Baseline thyroid hormone levels are not associated with cognitive decline: the ELSA‐Brasil study
Natalia G Gonçalves, Claudia Szlefj, Paulo A Lotufo, Isabela M Bensenor, Claudia Kimie Suemoto- Psychiatry and Mental health
- Cellular and Molecular Neuroscience
- Geriatrics and Gerontology
- Neurology (clinical)
- Developmental Neuroscience
- Health Policy
- Epidemiology
Abstract
Background
Thyroid dysfunction has been associated with cognitive decline and dementia. However, the role of subtle thyroid hormone alterations in cognitive function is still debatable. Additionally, most studies have been conducted in high‐income countries. The aim of this study was to investigate the longitudinal association between baseline thyrotropin (TSH), free thyroxine (FT4), and free triiodothyronine (FT3) levels with cognitive decline in the Brazilian Longitudinal Study of Adult Health (ELSA‐Brasil) during 8 years of follow‐up.
Method
Participants were evaluated every four years in three study waves (2008‐10, 2012‐14, and 2017‐19). Baseline TSH, FT4, and FT3 were collected after overnight fast and analyzed using immunoenzymatic assay. Cognitive performance was evaluated using the immediate and late recall, semantic and phonemic verbal fluency, and the trail‐making tests. A global composite z‐score was derived from these tests. Association of TSH, FT4 and FT3 levels with cognitive decline over time was evaluated using linear mixed‐effects models, adjusted for sociodemographic, lifestyle, and clinical variables.
Result
In 9,524 participants (mean age 51.2±8.9 y, 51% women, 52% White), the mean baseline TSH level was 2.3 ± 1.3 mIU/L, the mean baseline FT4 level was 1.2 ± 0.1 ng/dL, and the mean FT3 level was 0.2 ± 0.04 pg/mL (Table 1). There was no association between circulating TSH, FT4, and FT3 levels and cognitive decline during the follow‐up (Table 2 and Figure 1).
Conclusion
Thyroid hormone levels were not associated with cognitive decline in middle‐aged and older adults without overt thyroid dysfunction during 8 years of follow‐up.