Prevalence and Impact of Atrial Fibrillation on Intra-Hospital Mortality in Patients Aged ≥75 Years.

It is unclear whether the association between atrial fibrillation (AF) and intra-hospital mortality in patients aged 75 years and older is causal or not. This study aims (1) to describe the prevalence and clinical characteristics of AF in ≥75-year-old inpatients and (2) to study the association between AF and length of stay (LOS) and intra-hospital mortality. This retrospective cohort study includes consecutive patients aged ≥75 years admitted between January 2017 and December 2019 to a Belgian secondary hospital. Survival analysis was conducted on the whole dataset and a propensity score-matched dataset separately. Propensity score matching (PSM) was performed to account for the individual probability of having AF given a set of covariates. In 9,105 patients, 3,137 (34%) had a diagnosis of AF upon hospital admission. AF prevalence increased with age strata (from 29% to 38%), and Charlson Co-morbidity Index (from 28% to 57%). Intra-hospital mortality (20%) was higher in the AF group than in the AF-free group (25% vs 17%, p <0.001). The median LOS was 11 days and was shorter in those without AF (10 [4, 17] days) compared with those with AF (11 [5, 19], p <0.001). After PSM, AF was not associated with increased odds of LOS >10 days (odds ratio 1.08, confidence interval: 0.98 to 1.20, p = 0.13). The risk of intra-hospital death for patients with AF remained higher compared with those without AF (log-rank p = 0.0015 and hazard ratio 1.17; confidence interval: 1.04 to 1.32, p = 0.008). In conclusion, the prevalence of AF was high (34%) in inpatients aged ≥75 years and increased with age and co-morbidity burden. After PSM, patients with AF had a 17% higher risk of intra-hospital mortality than patients without AF.