Many people who suffer from irregular heartbeats (atrial fibrillation) which might cause stroke, need to take blood thinners to prevent it. It is important to prescribe the correct dose of blood thinners to the right patients to ensure the treatment works however avoiding complications. In the recent years, new blood thinners have been available; they require less laboratory tests and fewer visits to a doctor compared to older therapies. This study will look at how the general practitioners in the UK prescribe blood thinners according to the instructions given by the product manufacturer. We will use primary care data that is routinely collected by the general practitioners about their patients but without any possibility to identify individual patients. The results will help us to understand the magnitude of deviation from instructions in order to ensure that the patients benefit from the treatment.

Inclusion Criteria:

• All patients aged >= 18 years with at least one year of enrollment with the primary care practice and one year since first health contact recorded in the database THIN(The Health Improvement Network) or CPRD(Clinical Practice Research Datalink) prior to index prescription date will be included.
• Patients with first prescription of DOACs (rivaroxaban, dabigatran, apixaban) during the study period.
• Diagnosis NVAF (any time prior index date or within the 2 weeks after the index date)

Exclusion Criteria:

• Patients having the history of valvular replacement or mitral stenosis (prior to index date or 2 weeks after index-date)
• Patients who have any record of being prescribed their index drug prior to the enrolment period or who qualify as members of more than one cohort on the same day.

Population based on primary care databases representative of the UK population.

Availability of this study's data will be determined according to Bayer's commitment to the EFPIA/PhRMA "Principles for responsible clinical trial data sharing". This pertains to scope, timepoint and process of data access. As such, Bayer commits to sharing upon request from qualified researchers patient-level clinical trial data, study-level clinical trial data, and protocols from clinical trials in patients for medicines and indications approved in the US and EU as necessary for conducting legitimate research. This applies to data on new medicines and indications that have been approved by the EU and US regulatory agencies on or after January 01, 2014. Interested researchers can use www.clinicalstudydatarequest.com to request access to anonymized patient-level data and supporting documents from clinical studies to conduct research. Information on the Bayer criteria for listing studies and other relevant information is provided in the Study sponsors section of the portal.