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

Context: Several alterations in thyroid function test (TFT) results have been associated with mortality in elderly patients. Objective: Our aim was to investigate the relationship between TFT results and all-cause and cardiovascular (CV) mortality in aged hospitalized patients. Design: A 7-year prospective observational study was conducted. TFTs were performed at hospital admission, and mortality was registered in the follow-up period. Patients: Participants were 404 patients aged >65 years admitted to the Department of Geriatrics, Hospital General, Segovia, Spain, for any reason during 2005. Main Outcome Measures: The study evaluated the association between TFT results and mortality from all causes and CV diseases. Methods: TSH, free T-4, and free T-3 (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. Results: 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 T-4 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). Conclusions: 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.