Relação entre exposição à luz pela manhã, ciclo sono-vigília e atenção em adolescentes de Natal/RN

Abstract

Psychosocial, behavioral and physiological changes related to adolescence contribute to a phase delay in the sleep-wake cycle (SWC). However, early school starting time in the morning shorten sleep, causing partial chronic sleep deprivation and irregularity, resulting in excessive daytime sleepiness and impairing in cognitive and academic performance. Furthermore, SWC and attention present circadian variation and can be modulated by light-dark cycles. Therefore, this study aims to analyze the relationship between morning light exposure and SWC and attention in adolescents studying in the morning shift in Natal/RN. The study included 99 adolescents of both sexes (63 girls), aged 15.7 (±0.8) years, studying in freshmen and sophomore years of private high school. The students answered the “Health and Sleep” questionnaire and a Sleep Diary, containing the Maldonado sleepiness scale, and used an actimeter for 10 days. Actimetry collected data on SWC and light exposure. Attention was evaluated by a Continuous Performance Task (CPT), on a single application at school, between 7:30-9:30h. In general, the sample presents poor sleep quality, sleep irregularity, sleep deprivation. On free days, high light intensities were associated with sleeping (B=-38.43, p<0.05) and waking up (B=-63.29, p<0.05) earlier on free days and regular time in bed (B=- 51.34, p<0.05) as well as tendencies towards morningness (B=-24.91, p=0.07), less sleepiness when waking up on school days (B=-7.83, p=0.09) and regular waking up times (B=-17.67, p=0.09). In addition to shorter reaction time on tonic alertness (B = -32.87, p=0.05) and higher stability in sustained attention (B=-15.90, p=0.06). On the other hand, on school days, high light intensities were related to sleeping later (B=47.84, p<0.01) and shorter sleep duration (B=- 41.43, p=0.01) and time in bed (B=-47.22, p<0.01), as well as longer reaction times on tonic (B=58.74, p<0.05) and phasic alertness (B=84.54, p<0.05), and selective attention (B=67.37, p<0.05). On the day of the CPT, high levels of sleepiness upon awakening were related to a higher frequency of omissions on tonic alertness (B=0.31, p<0.05), while lower sleep latencies related to higher percentage of correct responses on phasic alertness (B=-0.16, p<0.05). Furthermore, high light intensities between wake-up and entering the classroom were associated with longer reaction times on tonic alertness (B=95.51, p<0.05), selective attention (B=150.44, p <0.05) and a trend towards phasic alertness (B=53.08, p=0.08). Light during classes (between 7-9:30h) was not associated with changes in attention. Therefore, high exposure to light on free days is associated to earlier sleep times in these days, more regular sleep and higher attentional performance. However, exposure on school days was associated with shortened sleep, which may be associated to exposure to artificial light at night. Thus, additional studies with larger sample size and analysis of nighttime light exposure are needed to clarify and confirm these relationships.