Svendsen JH, Diederichsen SZ, Højberg S, et al. - Implantable loop recorder (ILR) screening resulted in a three-fold increase in atrial fibrillation detection and anticoagulation initiation in people with stroke risk factors, but no significant reduction in the risk of stroke or systemic arterial embolism. Such findings may imply that not all atrial fibrillation warrants screening and that not all atrial fibrillation detected by screening warrants anticoagulation.

• A randomized controlled trial was carried out in four centres in Denmark.

• From January 31, 2014, to May 17, 2016, 6,205 people were screened for inclusion, and 6004 were chosen and randomly assigned: 1,501 (25·0%) to ILR monitoring and 4,503 (75·0%) to usual care.

• The mean age was 74·7 years (SD 4·1), with 2,837 (47·3%) women and 5,444 (90·7%) people with hypertension.

• There were no dropouts due to a lack of follow-up.

• Atrial fibrillation was diagnosed in 1,027 participants during a median follow-up of 64·5 months: 477 (31·8%) of 1,501 in the ILR group vs 550 (12·2%) of 4,503 in the control group.

• Oral anticoagulation was started in 1,036 candidates: 445 in the ILR group vs 591 in the control group, and the primary outcome occurred in 318 candidates (315 stroke, three systemic arterial embolism): 67 in the ILR group vs 251 in the control group.

• Major bleeding occurred in 221 candidates, with 65 (4·3%) in the ILR group and 156 (3·5%) in the control group.