Circadian typology is a latent trait that is usually assessed with scoring on a series of questions thought to represent the construct. But, in the classification, most people fall into the intermediate type, i.e. neither a definite morning nor an evening type, but still showing stronger preference towards either end of the continuum. Our aim was to operationalize chronotype using latent class analysis (LCA) for a 6-item scale derived from the original Horne-Östberg Morningness-Eveningness Questionnaire to compare and understand characteristics of chronotype in a population-based sample of adults in Finland. A total of 4904 men and women aged 25-74 years were included. We also analyzed the associations of chronotypes with physical activity (PA) and sitting. We found five latent chronotype groups including "rested more-evening type" (28%), "rested more-morning type" (24%), "morning type" (23%), "tired more-evening type" (17%) and "evening type" (8%) groups. Operationalization of chronotype by LCA suggests that morning alertness is an important feature differentiating chronotypes. Further, the "evening type" and the "tired, more-evening type" had higher odds for none to very low as well as low PA, as compared to "morning type". In addition, "evening type" was associated with higher odds for more time spent sitting, as compared to "morning type". Our findings indicate that it is important to assess sleep schedules and morning tiredness, which then could be targeted as a potential mediating factor for health behaviors, in particular, PA and health status.
Keywords: Chronotype; latent class analysis; morning tiredness; physical activity; sedentary behavior; sitting.