RESUMEN
BACKGROUND: The abrupt onset of the COVID-19 pandemic compelled universities to swiftly establish online teaching and learning environments that were not only immediately deployable but also conducive to high-quality education. This study aimed to compare the effectiveness of the online synchronous and asynchronous teaching formats in the dermatology lecture for undergraduate medical students, including academic performance, self-efficacy, and cognitive load. METHODS: A total of 170 fourth-year undergraduate medical students attending the dermatology lecture were included. The lecture was delivered using both the synchronous method (live online lecture via Webex meeting) and the asynchronous method (lecture videos shared on YouTube). The students had the freedom to choose their preferred method of attending the online lecture. The study assessed three main aspects: (1) learning outcomes measured through pretest, posttest, and retention test scores; (2) cognitive load experienced by students, including mental load and mental effort measured using eight items; and (3) satisfaction levels with each online teaching format. RESULTS: In this study, 70 students opted for the synchronous online lecture, while 100 students chose the asynchronous online lecture. Both synchronous and asynchronous teaching methods exhibited significant improvements in post and retention test scores compared to the pretest. Satisfaction levels, rated on a scale of 0-5, were generally high for both teaching methods, with no significant differences observed (4.6 for synchronous, 4.53 for asynchronous; p =.350). Regarding cognitive load, the synchronous method showed a significantly lower level than the asynchronous method (p =.0001). Subgroup analysis revealed no difference in mental effort (p =.0662), but the level of mental load was lower in the synchronous method (p =.0005). CONCLUSIONS: Both synchronous and asynchronous online teaching methods demonstrated improvements in learning outcomes and high levels of student satisfaction. However, the cognitive load experienced by students was lower in the synchronous setting compared to the asynchronous setting. These findings remind health professions educators that they would consider the students' cognitive load when designing online curricula.