Protein–energy malnutrition (PEM), which leads to a reduced ability of tissues to regenerate and repair themselves, may exacerbate many chronic diseases, including atrial fibrillation (AF), which occurs as a response of the heart to chronic inflammation. However, population-based studies examining the association between PEM and the prevalence and health care burden of AF are lacking. The aim of this retrospective cohort study was to estimate the impact of PEM on the prevalence and clinical outcomes of hospitalization for AF. The National Inpatient Sample (NIS) 2016 and 2017 datasets were searched for data on hospitalized adult patients with AF as a principal diagnosis; we subsequently identified AF patients with and without PEM as a secondary diagnosis using International Classification of Diseases, Tenth Revision (ICD-10), codes. The primary outcome of our study was inpatient mortality, while the secondary outcomes were hospital length of stay (LOS), total hospital cost (THC), cardiogenic shock, pacemaker insertion, successful ablation, and restoration of cardiac rhythm. Propensity score–weighted analysis was used accordingly to adjust for confounders. Out of 821,630 AF hospitalizations, 21,385 (3%) had PEM. Hospitalization for AF with PEM led to a statistically significant increase in mortality (adjusted odds ratio [aOR], 2.30; 95% confidence interval [CI], 1.93–2.75;
P
< .001) with an adjusted increase in the THC of $15,113 (95% CI, 11,246–18,980;
P
< .001), a 2-day increase in the LOS (95% CI, 1.92–2.41;
P
< .001), increased odds of cardiogenic shock (aOR, 1.36; 95% CI, 1.01–1.85;
P
= .04), and decreased odds of undergoing successful ablation (aOR, .71; 95% CI,.56–.88;
P
= .002) and achieving the restoration of cardiac rhythm (aOR, 0.56; 95% CI, 0.49–0.0.63;
P
≤ .001) compared to those without PEM. These results indicate that PEM is associated with worse in-hospital outcomes in patients with AF. This potential association suggests that nutritional rehabilitation may be essential for improving hospitalization outcomes in AF patients.