The Free Triiodothyronine/Free Thyroxine Ratio Is Associated with Frailty in Older Adults: A Longitudinal Multisetting Study
Abstract
Background: Various models have been proposed to predict frailty, including those based on clinical criteria and phenotypes. However, a simple biomarker associated with frailty has been not yet identified. The aim of this study is to evaluate the relationship between free triiodothyronine (fT3)/free thyroxine (fT4) ratio value and the degree of frailty among three different cohorts of older individuals: (1) acutely ill hospitalized patients, (2) nursing-home (NH) residents, and (3) home-dwelling centenarians.
Methods: We performed a secondary analysis of de-identified patient-level data from two prospective observational studies on acutely hospitalized older patients (Geriatric Acute Unit [GAU]), and home-dwelling centenarians (CENT), and a retrospective-prospective observational study on older NH residents. Demographic characteristics, along with a 30-items Frailty Index (FI) and serum thyrotropin, fT3 and fT4 measurements were obtained.
Results: Six hundred fifteen individuals (aged 86.4 ± 8.9 years; 55.1% females) were included in the study, including 298 (48.5%) GAU, 250 (40.6%) NH, and 67 (10.9%) CENT. A significant inverse relationship between fT3/fT4 ratio and FI values was observed (ρs = −0.17 [confidence interval; CI: −0.092 to 0.252], p < 0.001), and this was confirmed by logistic multivariate analysis (β = −0.44, odds ratio [OR]: 0.64 [CI: 0.47–0.87], p < 0.001) (after adjustment for age, sex, and cohorts). Moreover, a progressively decreased mortality risk was associated with rising fT3/fT4 ratio (OR 0.60 [CI: 0.44–0.80] β = −0.51, p < 0.001].
Conclusions: The fT3/fT4 ratio value was inversely correlated with frailty degree and mortality risk in a large cohort of older individuals, including centenarians, regardless of their sex and clinical condition. fT3/fT4 ratio value could represent an easily measured independent biochemical marker of frailty degree in older people.
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Copyright 2023, Mary Ann Liebert, Inc., publishers.
History
Published online: 14 February 2023
Published in print: February 2023
Published ahead of production: 15 January 2023
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Authors' Contributions
Conceptualization (supporting), formal analysis (lead), methodology (equal), writing—original draft (lead), and visualization (lead) by C.O. Conceptualization (equal), data curation (equal), supervision (equal), and writing—review and editing (equal) by B.A. Conceptualization (equal), data curation (equal), methodology (equal), and writing—original draft (lead) by V.C. Data curation (equal), investigation (equal), and methodology (equal) by S.C. and L.P. Data curation (equal) and formal analysis (equal) by R.F. Data curation (equal) and methodology (equal) by S.R. Conceptualization (equal), supervision (equal), and writing—review and editing (lead) by M.C. Methodology (supporting), supervision (equal), and validation (supporting) by D.M. Conceptualization (lead), data curation (lead), supervision (lead), writing—review and editing (equal), and project administration (lead) by G.V. Data curation (lead), project administration (lead), supervision (lead), and writing—review and editing (equal) by A.M. Conceptualization (lead), data curation (lead), supervision (lead), writing—original draft (lead), and methodology (equal) by F.M.
Author Disclosure Statement
No competing financial interests exist.
Funding Information
This study was supported by the Italian Ministry of Health: RCR-2021-23671216 (Ricerca Corrente Reti 2021).
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