Table 7.

Description of analyzed studies on sleep disorders, according to the PICOS ¹ method.

Study	Participants	Interventions	Comparisons	Outcomes	S. Design
Warzak et al. (2011) [37]	201 children; ages 5–12	Caffeine intake: 52–109 mg/day	Evaluation of enuresis and sleep history	Caffeine reduces total sleeping time	Cross-sectional
Calhoun et al. (2011) [38]	77 children with excessive day drowsiness; ages 5–12	Caffeine intake questionnaire	Caffeine vs. no caffeine 2: polysomnography	Caffeine is not associated to excessive day drowsiness	Cross-sectional
Calamaro et al. (2012) [39]	625 children; ages 6–10	Caffeine intake: 1–5 cans of soda or cups of coffee per day	Low caffeine intake vs. high caffeine intake by frequency questionnaires	Caffeine produces 15 minutes less of sleep per night	Cross-sectional
Katz, et al. (2014) [40]	210 children; ages 9–15	Drug testing	Caffeine detected or undetected by drug testing	Caffeine increases start of sleep by 4 minutes	Retrospective analysis
Watson et al. (2017) [41]	309 children; ages 8–12	Caffeine intake: 0–151 mg/day	Caffeine versus no caffeine	Caffeine is related to sleep disorders	Cross-sectional

¹ PICOS = P: participants; I: interventions; C: comparisons; O: outcomes; S: study design. ² Other variables besides caffeine were considered in this study.