Correlation analysis of FT3/FT4 and frailty in elderly patients with coronary heart disease

In previous studies on thyroid hormones and frailty, most of the target population were elderly, and there were relatively few studies on elderly patients with coronary heart disease (CHD). Inflammation, oxidative stress, and haemodynamic instability in cardiovascular disease (CVD) can influence fluctuations in thyroid hormone (TH) levels and increase the incidence of frailty. The purpose of the present study was to explore the effect of TH on the risk of frailty in elderly patients with CHD.

The Fried scale was used to assess the frailty of participants. The predictive value of TH for frailty was determined using the patient's operating characteristic curve. Multivariate logistic regression model was utilised to analyse the relationship between TH and frailty.

A total of 277 elderly patients with CHD were included in the study, of whom 29.96% were in a state of frailty. Free triiodothyronine (FT3)/free thyroxine (FT4) predicted frailty with the largest area under the curve of 0.634. Unordered multinomial logistic regression analysis showed that a lower T3 level was a risk factor for pre-frailty (p < 0.05). Lower levels of T3, FT3, and FT3/FT4 were risk factors for frailty (p < 0.05) after adjusting for demographic variables and blood indexes.

The predictive value of FT3/FT4 for frailty was more accurate than that of a single index. Moreover, T3 ≤ 1.095 nmol/L, FT3 ≤ 4.085 pmol/L, and FT3/FT4 ≤ 0.336 were shown to be the influencing factors of frailty, while T3 ≤ 1.095 nmol/L is an independent risk factor pre-frailty. Clinicians should focus on timely identification of the risk of frailty in order to improve patient quality of life and to reduce the risk of complications.