Shortening of sleep length and delayed mid-sleep on free days are the characteristic features of predominantly morning active population of Indian teenagers

We studied patterns in the distribution of chronotype and sleep–wake behavior in a randomly chosen sample population of Indian teenagers consisting 965 school-going children. All of them voluntarily responded on two structured inventories, namely truncated version of the morningness–eveningness questionnaire (MEQ) to assess chronotype and the Munich Chronotype Questionnaire (MCTQ) to determine sleep–wake variables on both work and free days. The results revealed that a majority of teens were predominantly morning active (59%), about 33% were intermediate, whereas only 8% were evening type. The mid-sleep on free days (MSF) in most of the subjects was 1 h delayed compared to those on work days. The MSF in adolescent was identified as the primary predictor of social jetlag. The average sleep duration was recorded to be less than 7 h on both school and free days. The evening chronotype teenagers were significantly sleeping less with more social jetlag and delayed mid-sleep than morning or neither type. This study gave an insight on the prevalence of lark chronotype and shorter sleep among Indian teenagers.