title: Exposure to bright light during evening class hours increases alertness among working college students.
abstract: OBJECTIVE
  To evaluate the effects of exposure to bright light on sleepiness during evening hours among college students.
  
  
  METHODS
  Twenty-seven healthy college students, all males, with ages ranging from 21 to 24years, working during the day and studying in the evening, participated in this study. During the 3week study, the students wore actigraphs and recorded levels of sleepiness. In a crossover design, on the second and third weeks, the students were exposed to bright light (BL) at either 19:00 or 21:00h. Salivary melatonin samples were collected before and after BL exposure. ANOVA test for repeated measurements were performed.
  
  
  RESULTS
  After BL exposure, sleepiness levels were reduced at 20:30 and 22:00h (F=2.2; p<0.05). ANOVA showed statistical differences between time (F=4.84; p=0.04) and between day and time of BL exposure (F=4.24; p=0.05). The results showed effects of melatonin onset at 20:00 and 21:30h and sleepiness levels (F=7.67; p=0.02) and perception of sleepiness and intervention time (F=6.52; p=0.01).
  
  
  CONCLUSIONS
  Controlled exposure to BL during evening hours increased alertness among college students. The effects of BL on sleepiness varied according to the time of melatonin onset.
authors.affiliation: National School of Public Health, FIOCRUZ, 1480 Leopoldo Bulhões St., Office 17, Rio de Janeiro 21041-210, RJ, Brazil. lilianeteixeira@ensp.fiocruz.br
authors.forename: Liliane
authors.initials: L
authors.lastname: Teixeira
authors.forename: Arne
authors.initials: A
authors.lastname: Lowden
authors.forename: Andréa Aparecida da
authors.initials: AA
authors.lastname: Luz
authors.forename: Samantha Lemos
authors.initials: SL
authors.lastname: Turte
authors.forename: Claudia Roberta
authors.initials: CR
authors.lastname: Moreno
authors.forename: Daniel
authors.initials: D
authors.lastname: Valente
authors.forename: Roberta
authors.initials: R
authors.lastname: Nagai-Manelli
authors.forename: Fernando Mazzilli
authors.initials: FM
authors.lastname: Louzada
authors.forename: Frida Marina
authors.initials: FM
authors.lastname: Fischer
mesh_terms: D056044:Actigraphy; D001143:Arousal / Q000528:radiation effects*; D018592:Cross-Over Studies; D006801:Humans; D008027:Light; D008297:Male; D013334:Students / Q000523:psychology; D014851:Wakefulness / Q000528:radiation effects; D055815:Young Adult