Association of onset time of new-onset atrial fibrillation with in-hospital mortality among critically ill patients: A secondary analysis of a prospective multicenter observational study

BACKGROUND: New-onset atrial fibrillation (AF) in critically ill patients is associated with adverse outcomes. In non-critical settings, the circadian variation in paroxysmal AF is of significant interest; however, circadian variation in critically ill patients with new-onset AF has not been thoroughly studied. This study aimed to examine the association between AF onset time and in-hospital mortality. METHODS: This was a secondary analysis of a prospective multicenter observational study enrolling adult critically ill patients. According to AF onset time, patients were divided into nighttime (0:00–7:59), daytime (8:00–15:59), and evening (16:00–23:59). We conducted a multiple logistic regression analysis to assess the potential association between AF onset time and in-hospital mortality. We also assessed the distribution of AF onset, crude in-hospital mortality, and adjusted in-hospital mortality according to bihourly intervals. RESULTS: Of 423 patients, in-hospital mortality was 26%. During nighttime, 135 patients (32%) developed new-onset AF. AF emerged during daytime for 141 (33%) and during evening for 147 (35%). Daytime AF was significantly associated with an increased risk of in-hospital mortality (adjusted OR: 1.92; 95% CI: 1.07–3.44; p = 0.030). Bihourly interval analysis showed that adjusted in-hospital mortality was unevenly distributed and bimodal with troughs between 6:00 and 7:59 and between 18:00 and 19:59. A similar trend was seen in the distribution of the number of new-onset AF. CONCLUSIONS: We found that the bihourly adjusted in-hospital mortality was distributed in a bimodal fashion. Further research is needed to determine the causes of the diurnal variation and its impact on patient outcomes.