MON-369 - The Silent Thyroid Threat: Subclinical Hypothyroidism Predicts Worse Survival in HFpEF - A National Inpatient Sample Study

Background

Subclinical hypothyroidism (SCH), characterized by elevated thyroid-stimulating hormone (TSH) levels with normal free T4, is a common endocrine condition with a prevalence of 3–15% in the general population [1]. Emerging evidence suggests that SCH may contribute to cardiovascular morbidity and mortality; however, its specific impact on heart failure with preserved ejection fraction (HFpEF) remains poorly understood. Large-scale, population-based studies examining the association between SCH and adverse outcomes in HFpEF are limited.

Methods

We conducted a cross-sectional retrospective analysis using the National Inpatient Sample (NIS) database from 2016 to 2021. International Classification of Diseases, Tenth Revision (ICD-10) codes identified adult patients (≥18 years) with primary or secondary diagnoses of isolated HFpEF and HFpEF with concurrent SCH. Survey-weighted statistical analyses were performed using STATA v17 to account for the complex NIS sampling design and produce nationally representative estimates.

Results

Among 12,909,035 heart failure hospitalizations, 9,035 patients had SCH, of whom 3,460 had HFpEF with SCH. The cohort had a mean age of 69.8 years, equal gender distribution (50% female, 50% male), and predominantly White race (64%), followed by Black (16%) and Hispanic (12%). Income distribution was balanced: < $46K (25%), $46K– < $59K (26%), $59K– < $79K (26%), and >$79K (23%). Most patients were treated at urban teaching hospitals (77%). Regional distribution was relatively even, with the South accounting for 33%, Northeast and West 23% each, and Midwest 21%. Key comorbidities included hypertension (85%), coronary artery disease (45%), atrial fibrillation (45%), valvular disease (33%), and renal failure (48%).

Compared with isolated heart failure, patients with HF and SCH had higher in-hospital mortality (adjusted odds ratio 0.58, 95% CI 0.35–0.96, p=0.03) and longer length of stay (mean 6.97 days, 95% CI 6.93–6.99, p=0.01). Among HFpEF patients specifically, SCH was associated with significantly increased mortality (adjusted odds ratio 0.51, 95% CI 0.31-0.83, p=0.007).

Conclusion

In this large, nationally representative analysis of over 12.9 million heart failure hospitalizations, subclinical hypothyroidism was independently associated with increased in-hospital mortality and prolonged length of stay in patients with HFpEF. Given the high prevalence of SCH and the growing burden of HFpEF, prospective studies are urgently needed to evaluate whether thyroid hormone replacement therapy can improve clinical outcomes and reduce mortality in this high-risk population.

References
1) Gosi SKY, Kaur J, Garla VV. Subclinical Hypothyroidism. [Updated 2024 Feb 15]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK536970/

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