title: Caffeine intake reduces sleep duration in adolescents.
abstract: In our study, we hypothesized that higher caffeine intake would be associated with lower sleep duration among 13-year-old adolescents. In addition, we aimed to identify food sources of caffeine intake in this sample. Eligible participants were adolescents who were born in 1990 and attended school in Porto, Portugal, in 2003/2004. Self-administered questionnaires were used, and diet was evaluated using a food frequency questionnaire. From the 2160 eligible participants, only 1522 with valid information regarding their diet were included in this study. In our sample, the median intake of caffeine was 23.1 mg/d, with soft drinks being the major source. Ice tea presented the highest median (25th-75th percentiles) contribution (33.1% [14.0-52.1]), followed by cola (21.1% [6.4-37.6]). Regarding cocoa products, chocolate bars presented a median contribution of 5.1% (1.0-14.0), and snacks containing chocolate had a contribution of 3.0% (0.5-7.2). Coffee and tea presented a negligible contribution. Adolescents who reported less sleep duration and those who spent more time watching TV during the weekend had a significantly higher caffeine intake. Overall, boys had higher intakes of caffeine from soft drinks, and private school attendees, those who had parents with more education, who reported less television viewing time and had lower body mass index presented higher intakes of caffeine from chocolate. Considering sleeping more than 9.5 hours as a reference class, for each increase of 10 mg/d in caffeine intake, we found that the odds ratio of sleeping 8.5 hours or less was 1.12 (95% confidence interval, 1.06-1.19). Our results support the hypothesis that caffeine intake was inversely associated with sleep duration in adolescents.
authors.affiliation: Department of Clinical Epidemiology, Predictive Medicine and Public Health, University of Porto Medical School, Porto, Portugal; Department GF Ingrassia, University of Catania, Catania, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Lodato
authors.forename: Joana
authors.initials: J
authors.lastname: Araújo
authors.forename: Henrique
authors.initials: H
authors.lastname: Barros
authors.forename: Carla
authors.initials: C
authors.lastname: Lopes
authors.forename: Antonella
authors.initials: A
authors.lastname: Agodi
authors.forename: Martina
authors.initials: M
authors.lastname: Barchitta
authors.forename: Elisabete
authors.initials: E
authors.lastname: Ramos
mesh_terms: D000293:Adolescent; D002099:Cacao / Q000737:chemistry; D002110:Caffeine / Q000008:administration & dosage*; D002182:Candy; D002253:Carbonated Beverages / Q000032:analysis; D003069:Coffee / Q000737:chemistry; D003430:Cross-Sectional Studies; D004032:Diet; D005247:Feeding Behavior; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D016017:Odds Ratio; D011174:Portugal; D012890:Sleep / Q000187:drug effects*; D011795:Surveys and Questionnaires; D013662:Tea / Q000737:chemistry; D013690:Television; D013997:Time Factors
chemical_list: D003069:Coffee; D013662:Tea; D002110:Caffeine
keywords: Adolescent; BMI; CI; Caffeine; Cross-sectional study; Epidemiology; FFQ; Food; OR; Sleep duration; body mass index; confidence interval; food frequency questionnaire; odds ratio