Background and purpose: Post-stroke infection (PSI) is a common and it is associated with a severe prognosis. Recent studies have shown that thyroid hormones play critical roles in the immune system regulation. However, association between PSI and thyroid hormone have not been fully elucidated. We therefore investigated the impact of thyroid hormone on PSI in acute stroke patients.
Methods: We retrospectively enrolled 520 consecutive patients with acute ischemic stroke (326 male, 71.9 ± 13.2 years) admitted to our department between September 2014 and June 2016. Serum thyroid stimulating hormone (TSH), free triiodothyronine (FT3), and free thyroxine (FT4) were evaluated upon admission. PSI was defined as infection occurring during hospitalization. The impact of the thyroid hormone on PSI was evaluated using multiple logistic regression analysis. Separate analyses were conducted according to PSI and quartile serum FT3 concentration.
Results: PSI was diagnosed in 107 patients (20.6 %). The most common infection was pneumonia with the prevalence of 65 patients (60.7 %), followed by urinary tract infection recorded in 19 patients (17.8 %). Age (P < 0.001), body mass index (P = 0.0044), pre-admission mRS (P = 0.002), NIHSS score on admission (P < 0.001), admission FT3 (2.63 ± 0.49 pg/mL vs. 2.24 ± 0.66 pg/mL, P < 0.001), and cardio-embolic stroke (P < 0.001) were significantly associated with PSI, but no relationship between TSH (2.84 ± 8.12 mIU/L vs. 2.20 ± 1.45 mIU/L, P = 0.4610), FT4 (1.22 ± 0.21 ng/dL vs. 1.21 ± 0.28 ng/dL, P = 0.1478), and PSI were found. On multivariable logistic regression analysis, low FT3 (< 2.29 pg/mL; odds ratio [OR], 2.96; 95% confidence interval [CI], 1.61- 5.45; P = 0.0005) and high admission NIHSS score (≥ 9 points, OR, 7.65; 95% CI, 4.10-14.73; P<0.0001) were independently associated with PSI. In comparisons between PSI and FT3 quartiles (Q1 [≤ 2.25 pg/mL], Q2 [2.26-2.55 pg/mL], Q3 [2.56-2.89 pg/mL], Q4 [≥ 2.90 pg/mL]), patients with PSI were significantly more frequent in Q1 than in Q2, Q3, and Q4 after multivariate adjustment.
Conclusions: Our results showed that a low FT3 at admission should be associated with PSI in acute ischemic stroke patients.