If the Morning-Evening Questionnaire (MEQ) is able to predict the actigraphy-based acrophase, how does its reduced, five-item version (rMEQ) perform?

We have recently shown that the score of the Morning-Evening Questionnaire (MEQ) can be used to predict the acrophase measured by actigraphy. The MEQ score was very well correlated with the acrophase, and the linear regression equation linking the MEQ score to the acrophase indicate that a one-point increase in the MEQ score is accompanied by a decrease of approximately 5 min in the acrophase. In the present follow-up we aimed to evaluate if also the score of the shorter version rMEQ is capable of satisfactorily predicting the acrophase, and what its performance is. Therefore, we returned to the original database and calculated the rMEQ through 5 items (1, 7, 10, 18, and 19). The same regression analysis procedures were applied generating a new linear equation for rMEQ to predict the acrophase. The current analysis showed a weaker but still reasonably good association between the rMEQ and the acrophase, as compared to our previous results based on the MEQ. The finding that rMEQ provides a prediction of the acrophase that is only slightly worse than the one provided by the complete questionnaire is very good for the investigators. The combination of both original and current report supports the conclusion that the MEQ questionnaire, both standard or reduced version, can be used to derive a prediction of the actigraphy-based acrophase in a population with a restricted age range and comparable morning activity schedule.