Prognostic Impact of Thyroid Function in Patients With Incident Heart Failure: A Nationwide Study.

Background: There is a paucity of data on the prognostic impact of thyroid dysfunction in patients with heart failure (HF). We aimed to examine the association between these 2 conditions in a nationwide cohort of patients with HF.

Methods: This Danish cohort study evaluated the thyroid function of patients diagnosed with first-time HF from 2000-2021. Patients were categorized according to laboratory-based thyroid-function values (euthyroid, overt/subclinical hypothyroidism or hyperthyroidism) recorded within 1 year before the HF diagnoses. The primary outcome was a composite of mortality and hospitalization due to HF, examined using the cumulative incidence function. Cox proportional hazard analysis adjusted for major comorbidities was performed to investigate differences in outcomes among groups.

Results: Of the 58,067 individuals included in this study (43.9% female, median age 75.7 years [p25-p75:66.4-83.5]), 54,319 (93.6%) were euthyroid, 1669 (2.9%) had subclinical hypothyroidism, 239 (0.4%) had overt hypothyroidism, 1633 (2.8%) had subclinical hyperthyroidism, and 207 (0.4%) had overt hyperthyroidism. Compared with euthyroid patients, the adjusted 1-year HR of the composite outcome was 1.11 (95% CI, 1.02-1.20) in patients with subclinical hypothyroidism, 1.24 (95% CI, 1.02-1.51) in patients with overt hypothyroidism, 1.06 (95% CI, 0.98-1.15) in patients with subclinical hyperthyroidism, and 1.27 (95% CI, 1.00-1.60) in patients with overt hyperthyroidism. This positive association was driven mainly by the increased mortality rates.

Conclusion: In patients with incident HF, the presence of both hypo- and hyperthyroidism up to 1 year prior to HF diagnosis was associated with increased risk of the composite of mortality and hospitalization for HF. Our results demonstrate a high-risk group of patients in need of increased clinical awareness.