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 …