Parameter identification and definition
At baseline (Day 0), subjects without any history of COVID-19 and AF conditions for two years were enrolled over an 8-month period with incident (new) COVID-19 conditions occurring first and subsequently followed by incident AF outcomes by at least one day. Individuals with co-exiting COVID-19 and AF cases during the same reporting day and any new AF conditions prior to incident COVID-19 cases were excluded from this study. The co-morbid history was identified on the basis of ICD10 codes (please see supplemental table S1 for ICD 10 codes), including: congestive heart failure, hypertension, diabetes mellitus, stroke, vascular disease, valvular disease, coronary artery disease, sleep apnea, chronic kidney disease, chronic obstructive pulmonary disease/bronchiectasis, major bleeding, cognitive impairment, lipid disorders, liver disease, anemia, depression, spondylosis/intervertebral discs, and osteoarthritis.
The first incidence of COVID-19 was determined as the first case upon entry into the study using the US CDC code of ‘U072’ (designated for confirmed cases starting April 1 2020). An incident AF outcome was defined as occurring as at least 1 day after the development of a COVID-19 conditions. It was defined in terms of ICD 10 codes as reported in supplemental table S1. The incident AF cases should have had no history of conditions during the 2-year baseline period as defined in terms of ICD10 codes (see supplemental table S1) and anticoagulant/rhythm control medications (see supplemental tables S2 and S3). Two demographic variables were utilized in this investigation, namely, gender and age. Age was defined as a continuous variable or in 5 categories (18-45, 45-55, 55-65, 65-75, 75-90 years). It was calculated in reference to the first month of enrolment upon entry into the study.