Poster #104 - Chronotype During the Transition From Adolescence to Young Adulthood

• In Event: 2-055 - Poster Session 06
  In Poster Session: PS 06 Section - Health, Growth, Injury

Integrative Statement

Most adolescent sleep research has focused on sleep duration and quality. Less attention has been given to an underappreciated facet of sleep: chronotype. Chronotype refers to one’s proclivity for particular sleep-wake timings that is largely driven by an individual’s circadian rhythm (Roenneberg et al., 2003). Traditionally, chronotype is dichotomized into morning-types and evening-types: morning-types report early bedtimes and wake times whereas evening-types report late bedtimes and wake times. Research among adults suggests that evening chronotypes fair worse on many outcomes compared to morning chronotypes. For instance, evening-types engage in more risky behaviors and report more depressive symptoms compared to morning-types (Killgore, 2007). Previous cross-sectional research suggests that chronotype changes over the lifecourse whereby most individuals start as morning chronotypes during childhood, shift toward an evening chronotype in adolescence, and revert back to a morning chronotype in adulthood. The trend toward eveningness that is a hallmark of the adolescent period amplifies the need to further understand chronotype and its predictive ability. The current study had the following aims: (1) estimate the stability of individual differences in chronotype during adolescence, (2) explore the developmental change in chronotype during adolescence, and (3) assess whether chronotype is predictive of depressive symptoms and risk-taking behaviors.
An ethnically-diverse sample of 316 tenth and eleventh grade adolescents (Mage=16.40, SD=0.74; 57% female) were recruited to participate in a longitudinal study. Data collection spanned three waves with each wave occurring two years after the previous one. Participants wore actigraphs – wrist-watches that estimate sleep from movement – for at least eight nights at each wave. Following established procedures, chronotype was determined by computing each individual’s midsleep point (MSP): the halfway time point between bedtimes and wake times on free days (Roenneberg et al., 2004). An earlier MSP indicates a morning chronotype, whereas a later MSP indicates an evening chronotype. Chronotype was estimated using free days, such as weekend days or holidays, as these days are free of scheduled bedtimes and wake times that would influence the MSP. Participants also completed questionnaires measuring risky behaviors and depressive symptoms.
Correlation analyses demonstrated that chronotype remains stable during adolescence such that chronotype was positively significantly associated across waves (waves 1-2: r=.192, p=.018; waves 2-3: r=.350, p<.001; waves 1-3: r=.299, p=.002). Multilevel modeling indicated that chronotype moved toward eveningness as adolescents became older, b(SE)=.38(.03), p<.001. Additionally, Asian Americans had a later chronotype and showed a more rapid developmental trend toward eveningness than their European American peers, b(SE)=.44(.18), p=.015. The implications of chronotype for adjustment depended upon age and gender. First, a significant chronotype by age interaction in predicting depressive symptoms emerged whereby a later chronotype predicted increased depressive symptoms for older adolescents, b(SE)=.03(.01), p<.001. Second, chronotype interacted with gender in predicting risk-taking behaviors such that males who exhibited later chronotypes engaged in more risk-taking, whereas the same association did not exist for females, b(SE)=-.09(.03), p=.004.
Chronotype remains stable across the transition from adolescence to adulthood, with important implications for adolescent and young adult sleep and sleep interventions.

Authors

• Maira Karan, University of California, Los Angeles
  Presenting Author

• Sunhye Bai, The Pennsylvania State University
  Non-Presenting Author

• Andrew J Fuligni, UCLA
  Non-Presenting Author