Validity and Reliability of the Korean Version of Reduced Morningness-Eveningness Questionnaire: Results From a General Population-Based Sample.

Background: Chronotype refers to individual variations in diurnal preferences that manifest as everyday behaviors, including sleep patterns. Traditionally, the Horne & Östberg Morningness-Eveningness Questionnaire (MEQ), which comprises of 19 items, has been the standard for determining chronotype. However, its length makes it cumbersome for widespread application. To address this issue, the reduced MEQ (rMEQ), a concise version containing only five items from the MEQ, was developed for a more practical approach to chronotype assessment. This study aimed to evaluate the validity and reliability of Korean version of rMEQ in a sample from the general Korean population.

Methods: The Korean version of the rMEQ comprises of items 1, 7, 10, 18, and 19 of the original MEQ. The validity of the rMEQ was assessed by correlating its scores with those of the MEQ and Munich Chronotype Questionnaire (MCTQ). Its reliability was determined by calculating internal consistency.

Results: A total of 3,030 individuals participated in the study, yielding an average rMEQ score of 14.0 ± 3.4. There was a substantial positive correlation between the rMEQ and MEQ scores (r = 0.859, P < 0.001). Furthermore, the rMEQ scores were significantly negatively correlated with the midpoint of sleep on free days corrected for sleep debt as measured by the MCTQ (r = -0.388, P < 0.001), indicating a robust association with chronotype. The internal consistency of rMEQ, measured using Cronbach's alpha, was 0.609.

Conclusion: This study finds the Korean version of the rMEQ to be a valid and reliable instrument for assessing chronotype in the general population.