Thyroid Function Tests and Mortality in Aged Hospitalized Patients: A 7-Year Prospective Observational Study

Abstract

Several alterations in thyroid function test (TFT) results have been associated with mortality in elderly patients. Our aim was to investigate the relationship between TFT results and all-cause and cardiovascular (CV) mortality in aged hospitalized patients. A 7-year prospective observational study was conducted. TFTs were performed at hospital admission, and mortality was registered in the follow-up period. Participants were 404 patients aged >65 years admitted to the Department of Geriatrics, Hospital General, Segovia, Spain, for any reason during 2005. The study evaluated the association between TFT results and mortality from all causes and CV diseases. TSH, free T₄, and free T₃ (FT₃) were measured on the first day of admission. In-hospital and total survival times, number of deaths, and all-cause and CV mortality were registered until the census date on January 1, 2012. During the study, 323 patients (80%) died. Kaplan-Meier analysis showed that median survival time for all-cause mortality was significantly lower in patients in the first tertile of serum FT₃, in the first tertile of TSH, and in the first tertile of serum free T₄ concentrations. Multivariate adjusted Cox regression analysis showed that the history of cancer (hazard ratio, 1.60; 95% confidence interval, 1.12-2.28; P = .009), age (1.03; 1.01-1.06; P = .003), and FT₃ levels (0.72; 0.63-0.84; P < .001) were significant factors related to all-cause mortality. The cause of death was known in 202 patients. Of this group, 61 patients (30.2%) died of CV disease. Patients in the first tertile of TSH and FT₃ exhibited a significant higher mortality due to CV disease. In the adjusted Cox regression analysis, FT₃ was a significant predictor of CV mortality (0.76; 0.63-0.91; P = .004). Alterations in TFT results during hospitalization are associated with long-term mortality in elderly patients. In particular, low FT₃ levels are significantly related to all-cause and CV mortality.