This is an observational study in which data collected from the past of patients with non-valvular atrial fibrillation (NVAF) is studied.

NVAF is a condition in which patients suffer from irregular and often rapid heartbeats which are not caused by a heart valve problem. NVAF can lead to thromboembolism, a condition that happens when a blood clot forms in the body and travels through the blood stream to plug another vessel. To prevent thromboembolism doctors often prescribe a blood thinner medication.

In patients with NVAF that receive a blood thinner, it is common that the kidneys' ability to work properly, also called the kidney function, decreases. This may increase the risk of stroke, a condition which occurs when a vessel supplying blood to the brain is blocked and the risk of bleeding. It is therefore important to maintain the kidneys' ability to work properly in these patients who are treated with blood thinners.

In the beginning, only one blood thinner that could be given as a tablet by mouth was available. This blood thinner was called warfarin. Over the years, further medications have become available, for example dabigatran or rivaroxaban. There is some evidence that a decrease of the kidney function is more common with warfarin than with dabigatran or rivaroxaban. For other similar new treatments however, evidence is missing or conflicting. There also could be other relevant factors such as the kidney function before the start of treatment or the patient's genes/origin.

In this study researchers want to collect more data to compare two different blood thinner medications, rivaroxaban and warfarin. The main goal is to see whether there is a difference between the two treatments regarding the kidneys' ability to work properly. To find this out, the researchers will compare the number of patients in each group who developed chronic kidney disease stage 5 (close to or corresponding to chronic kidney failure), had a kidney transplant or needed to undergo long term dialysis. In addition, data is collected and compared about the patients' age, gender, weight, height and whether they had other related medical problems.

This study will collect information from the health records from the Korean National Health Insurance Corporation (NHIC) database. Besides this data collection, no further tests or examinations are planned in this study. Researchers will look at the health information from adult men and women in Korea who were diagnosed with NVAF between January 2013 and December 2017. They will study data of the patients who did not receive any medication with blood thinners in past 24 months before starting rivaroxaban and warfarin treatment between January 2015 and December 2017. They will follow up all the participants until December 2018.

Inclusion Criteria:

• Be ≥20 years of age (legal age in Korea) at the time of anticoagulation initiation
• Have a diagnosis of NVAF (in the 24-months prior to index date)
• Have no record of OAC use (in the 24-months prior to index date)
• Newly initiated on rivaroxaban or warfarin (index date)

Exclusion Criteria:

• Who have end-stage renal disease or are on dialysis (in the 12-months prior to index date)
• With evidence of valvular heart disease (in the 12-months prior to index date)
• With pulmonary embolism or deep vein thrombosis (within 6 months before index date)
• Who received joint replacement (within 6 months before diagnosis)
• Patients who had previous OAC prescription between 2013 and 2014
• With rivaroxaban doses other than 15 or 20 mg once daily

Study is conducted using administrative claims data of the Korean National Health Insurance Service (NHIS) and the linked health check-up database of the National Health Insurance Corporation (NHIC) between 2013 to 2018.

Availability of this study's data will later 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.vivli.org 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 member section of the portal.