Sleep-wake cycle in rural populations

The light/dark cycle is the main zeitgeber acting on the mammalian circadian system; nevertheless, distinct environments, such as those with and without electricity may provoke important resetting effects on the clock. The aim of this study was to describe sleep/wake patterns of adolescents living in two Brazilian rural regions. In the first population, 120 adolescents participated in the study, 35 of whom did not have electricity at home. They filled out a questionnaire which included questions concerning their sleep habits. It was found that electricity at home influenced sleep patterns. Adolescents with electricity at home had later wake-up times on school days (p<0.05) and on weekends (p<0.05), and tendencies towards later bedtimes on school days (0.05 <0.10) and weekends (0.05 <0.10). In the second population, 461 adolescents filled out the same questionnaire, 66 of whom did not have television at home. ANOVA showed that having TV at home was related to later bedtimes during school days (p<0.05) and weekends (p<0.05). These results support the idea that sleep patterns are influenced by technological advances.