Circadian health differs between boys and girls as assessed by non-invasive tools in school-aged children.

Abstract

BACKGROUND & AIMS\nAssessment of circadian health is confined to adults. However, understanding circadian status of school-aged children is necessary due to its health implications. The aim was to develop 1) a protocol to assess circadian function in school-aged children by combining the best non-invasive tools previously validated in adults; 2) a score to capture circadian function in children including food timing. This protocol will allow to explore gender differences and to compare the circadian function of school-aged children with adults from the same Mediterranean area.\n\n\nMETHODS\nHealthy children (8-12\xa0y) from 3 schools in a Mediterranean area of Spain were recruited (n\xa0=\xa0248; 125 males and 123 females). Several non-invasive tools were used: a) 7-day-diaries of food timing and food intake, physical-activity and sleep, b) Munich-chronotype-self-reported-questionnaire; c) cortisol and melatonin saliva determinations; d) 7-day-rhythms of wrist temperature (T), activity (A), position (P) and the integrative variable TAP e) 7-day-light exposure.\n\n\nRESULTS\nWe have constructed the first school-aged children population for the assessment of circadian function (ONTIME-Jr) and a new circadian score has been developed. Among circadian-related measures, TAP was the most suitable and reliable to determine circadian system characteristics. Circadian function was better in girls than in boys [circadian score (AU) Mean\xa0±\xa0SD (girls, 1216\xa0±\xa0153 vs. 1159\xa0±\xa0173 boys, P\xa0=\xa00.012)], and also in school-aged children than in adults from the same Mediterranean area (Circadian-Function-Index: children 0.47\xa0±\xa00.06 vs. adults 0.45\xa0±\xa00.06\xa0P\xa0=\xa00.001).\n\n\nCONCLUSIONS\nA new protocol, including TAP and food timing, demonstrated to be reliable in assessing circadian function in children. These non-invasive techniques provide the wherewithal for paediatricians to assess circadian function in clinical practice.\n\n\nTRIAL REGISTRATION\nChronobiology and childhood obesity (ONTIME-Jr: Obesity, Nutrigenetics, Timing and Mediterranean, Junior). ClinicalTrials.gov ID: NCT02895282, October 2014.