BACKGROUND: Secure messaging use for clinician-to-clinician communication has grown rapidly in recent years. OBJECTIVE: To examine the association between secure messaging use, electronic health record (EHR) time, and frequency of attention switching among clinicians primarily working in an inpatient setting. DESIGN: Retrospective cohort study. PARTICIPANTS: Attending physicians, trainee physicians, and advanced practice providers who worked in an inpatient setting during a 3-month period (February-April, 2023) from 14 hospitals within a large midwestern health system. MAIN MEASURES: Secure messaging use (i.e., Epic Secure Chat) was measured as the total number of messages sent or received between clinicians, aggregated at the clinician-day level. The primary outcomes were EHR time (a measure for workload) and the frequency of patient switching (a measure for cognitive burden) within the EHR. Linear mixed-effect models were used to examine the association between daily secure messaging volume and the primary outcomes, adjusting for age, gender, patient load, and correlations within clinicians and clinical service assignments. KEY RESULTS: A total of 3996 clinicians (2174 [54%] female, median age 38 years [IQR 33, 48]) with 103,285 clinical work days, >
145 million audit log actions, and ~ 4.5 million secure messages were included. Median secure messaging volume was 9 (IQR 0, 51) messages per day, median EHR time was 250.5 min (IQR 140.3, 377.4) per day, and median number of patient switches was 79 (IQR 35, 147) per day. An increase in secure messaging volume from the 25th to 75th percentile was associated with a 25.5 min (95% CI 24.8, 26.2, p <
0.001) increase in EHR time and 18.1 (95% CI 17.6,18.6, p <
0.001) additional patient switches. CONCLUSIONS: Secure messaging use was associated with increased EHR time and frequency of attention switching. The results suggest that secure messaging use is associated with clinician work behaviors, potentially contributing to increased workload and cognitive burden.