Adolescent sleepiness linked to smartphone use, diet, and mental health in Brazilian teens

A study of Brazilian adolescents reveals a high prevalence of daytime sleepiness closely associated with smartphone addiction, poor diet, and emotional distress, highlighting complex intersecting health issues among youth.

In a public-school cohort from northern Minas Gerais, daytime sleepiness looked less like an isolated sleep complaint than part of a wider pattern of distress: 72% of 1,616 first-year secondary pupils met the threshold for excessive daytime sleepiness, while a companion analysis of the same teenagers found that 54.9% met criteria for smartphone addiction. Taken together, the studies suggest that poor sleep, heavy phone use, diet and emotional strain are clustering in the same adolescents rather than appearing as separate problems. (new.scielo.br)

The sleepiness paper, indexed by PubMed as an April 2026 article in Ciência & Saúde Coletiva, used the baseline phase of the ELCAS project, a two-stage study designed to follow adolescent behaviour, physical activity and health over time. Researchers surveyed boys and girls aged 14 to 19 in 20 state schools between September 2022 and December 2023, using the eight-item Pediatric Daytime Sleepiness Scale; a score of 15 or more counted as excessive daytime sleepiness, and the associations were modelled with Poisson regression and robust variance. (new.scielo.br)

The raw figures were striking even before adjustment. More than four in five girls in the sample were classified as sleepy during the day, compared with about three in five boys, and the adjusted analysis still showed a 22% higher prevalence among female pupils. School timetable also mattered: compared with pupils in the night shift, teenagers in morning or full-time schooling were 35% more likely to report excessive daytime sleepiness. The paper noted that about 95% of the cohort were studying in daytime shifts. (new.scielo.br)

Lifestyle patterns ran in the same direction. Adolescents in the pre-contemplation stage for exercise, meaning they had no intention of becoming physically active, were more likely to report excessive sleepiness than those in the maintenance stage, and daily consumption of ultra-processed foods was also independently associated with the condition. The authors reported that 31.3% of the teenagers consumed ultra-processed foods every day, while 71.1% were dissatisfied with their body image; in a sensitivity analysis using logistic regression, body-image dissatisfaction also emerged as significant, with an odds ratio of 1.37. (new.scielo.br)

The mental-health signal was harder still to ignore. In the sleepiness study, 86% of adolescents with severe depressive symptoms met the threshold for excessive daytime sleepiness, compared with 65.3% of those without severe symptoms, while 83.6% of those classed as smartphone-addicted were sleepy, versus 55.9% of those who were not. A separate paper from the same cohort found that smartphone addiction tracked not only with daytime sleepiness, but also with depression, stress, physical inactivity and poorer diet; in that analysis, daytime sleepiness showed the strongest association, with an adjusted prevalence ratio of 1.65. The companion study also found that 60.4% of the cohort had depressive symptoms, 62.5% had anxiety symptoms and 53.7% had stress symptoms. (new.scielo.br)

The Montes Claros findings fit an older Brazilian pattern, though differences in measurement are important. A 2021 Sleep Medicine study of 876 adolescents from three schools found a lower prevalence of excessive daytime sleepiness, 46.8%, but it used a stricter Pediatric Daytime Sleepiness Scale cut-off of 20 rather than 15. That study also found that physical activity was associated with lower sleepiness scores, while frequent consumption of processed foods and each additional hour spent on social media were linked to higher scores. Those differences help explain why the newer estimate is so much higher, and why direct comparisons between studies need caution. (pubmed.ncbi.nlm.nih.gov)

The researchers were careful not to claim cause and effect. Because the data were self-reported and drawn from first-year pupils in one Brazilian municipality, the study cannot show whether phone dependence, low mood or diet problems drive sleepiness, or whether persistent sleepiness worsens those problems. Even so, the authors wrote that excessive daytime sleepiness has “multifactorial causes”, while the smartphone paper said its findings “highlight the importance of interventions that promote healthy behaviors and provide psychological support for this population”. The ELCAS project includes a follow-up stage 24 months after baseline, which should offer a clearer picture of whether these risks intensify together or can be shifted through school-based and clinical intervention. (new.scielo.br)