Yoshida T, et al. - Researchers carried out landmark analysis and time-dependent Cox regression analysis to ascertain if sustained new-onset atrial fibrillation (AF) was correlated with stroke and death and to look for a possible dose–response relation between AF duration and death. Adult patients with new-onset AF were recruited in a prospective cohort study conducted in 32 intensive care units in Japan from 2017 to 2018. The authors discovered that hospital mortality was 25% and the incidence of in-hospital stroke was 4.6% among a total of 423 new-onset AF patients. In patients with AF duration longer than 48 h, the incidence of in-hospital stroke was 7.6% and in those with AF duration shorter than 48 h was 3.8%. Sustained new-onset AF was correlated with hospital mortality in ICU patients on a time-dependent basis, although with some uncertainty since in-hospital death or stroke was not related to AF duration longer than 48 h.