RESULTS (MLM)THE UNIVERSITY OF BRITISH COLUMBIAChronotype’s Effects on Health Across Countries   Lianjie (Marc) Shi, Steven HeineINTRODUCTIONMETHODSWhat is chronotype ?• Behavior manifestation of the underlying circadian rhythm which varies across individuals • Two general types: Night Owl and Morning Lark. • Suggested is more of a continuum than two extreme. Participants • 4941(5128) participants from 20 countries across 6 continents• With 250 participants per each country• All participants are of domestic cultural heritage Measurements  • Chronotype à Munich Chronotype Questionnaire (MCTQ)• Mental health level à PROMIS Global Mental • Physical health level à PROMIS Global Physical • Depression level à PROMIS Depression Statistical Analysis•Multilevel modeling (MLM)• individuals(level1) nested within countries(level2) Previous studies• There are Difference in chronotype across countries• People with Evening chronotype are associated with higher chance of physical and mental illness • Countries with more morning chronotype are NOT associated with higher health outcomes relative to countries with more evening chronotype. (WHO) Research question • What is the relationship between chronotype and health outcomesacross countries?Hypothesis • Chronotype’s effects on health outcomes is • Only significant for within-country level • Different across countries Predictors Estimate (CI) P-value Within Countries -0.75 [-1.08, -0.42] < .001Between Countries -2.19 [-5.00, 0.62] 0.440Variance between country 0.22 0.079Physical Health as outcome variableMental Healthas outcome variableDepressionas outcome variableCONCLUSION AND SIGNIFICANCEWithin Countries : • People with chronotypes that are later than the corresponding country’s average tend to have lower physical and mental health outcomes. • The effects of chronotype on countries are different from each other Between Countries: However, the analysis of between-country effects did not show any relationship between chronotype and people’s health outcomes. Significance • Our study’s findings highlight the importance of cultural fit in the relationship between chronotype and health level, demonstrating that people’s chronotypes are most relevant for predicting people’s health in comparison with their own countries’ averagesReferences:Adan, A., Archer, S. N., Hidalgo, M. P., Di Milia, L., Natale, V., & Randler, C. (2012). Circadian Typology: A Comprehensive Review. Bailey, S. L., & Heitkemper, M. M. (2001). Circadian rhythmicity of cortisol and body temperature: Morningness-eveningness effects. Cheung, B. Y., Takemura, K., Ou, C., Gale, A., & Heine, S. J. (2021). Considering cross-cultural differences in sleep duration between Japanese and Canadian university students. Relationships between Chronotype and Health OutcomesPredictors Estimate (CI) P-value Within Countries -0.56 [-0.79, -0.33] < .001Between Countries -3.49 [-5.60, -1.37] 0.440Variance between country 0.10 0.707Predictors Estimate (CI) P-value Within Countries 0.07 [0.04, 0.11] < .001Between Countries 0.02 [-0.29, 0.25] 0.883Variance between country 0.10 0.102Between-Country Slope