Impairment of sleep quality and quality of life in bimodal chronotype individuals.

There is still insufficient data about the characteristics and clinical significance of the bimodal chronotype. We evaluated more than 1000 students with Morningness-Eveningness Questionnaire, Munich Chronotype Questionnaire (MCTQ), Pittsburgh Sleep Quality Index and 36-item Short Form Health Survey. Twelve percent of the sample was bimodal and they showed similar results to intermediate chronotype in MCTQ-chronotype and social jetlag, both different from morning and evening chronotypes. However, their quality of life and sleep quality were similar to evening types, both different from morning and intermediate types. We discuss if being bimodal would be a maladaptive aspect of circadian preference.