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Aim: The objective of this study was to describe the rhythm of respiratory syncytial virus (RSV) bronchiolitis seasonal outbreaks in hospitalized children. Methods: Data was collected from 1324 patients, who were admitted to our hospital with bronchiolitis, over an 11-year period, from 1994 to 2004. The epidemic onset was established according to the epidemic index. Virological diagnosis was made with immunofluorescent assay from nasopharyngeal washings. Rhythm study was carried-out by spectral analysis with the fast-Fourier transformed and cosinor method. Results: Epidemics begin in September (45%) and October (55%); the highest peak was observed in January, the minimum in August and the end in February (73%), March (18%) and April (9%). When the epidemic outbreak begins sooner, the end is sooner as well. Epidemic onset varies but not its length and the onset was less variable than its conclusion. Spectral analysis showed a 12-months cyclic period along the study years and cosinor analysis demonstrated significant circannual rhythm. When data was segregated by long and short hospital stay, no significant differences were found between the rhythms. Comorbid association among bronchiolitis, otitis and gastroenteritis was very common. Conclusion: Bronchiolitis epidemics onset and conclusion varies along time years in hospitalized infants and showed circannual rhythmicity with a 12-months period.

The aims of this study were: (1) to investigate the evolution of the sleep pattern in preterm newborns during their first month of life; (2) to assess the influence of light–dark on the sleep pattern; and (3) to compare this pattern with that of full–term newborns. The population consisted of 60 healthy, preterm newborns and 63 full–term newborns, divided into four age groups, 1 week apart, throughout the first month of life. Preterm newborns were further divided into five groups according to conceptional (corrected) age. An observer took note every 30 min, for 24 h, of sleep or wakefulness in every case. The average sleeping time in preterm groups according to postnatal age remained unchanged during the first month of life: 17.57 honday 1 and 17.15h on day 28. When the preterm infants were re–grouped according to conceptional age, average daily sleep was 17.86 h at 32 weeks and 15.22 h at 37 weeks. The full–term newborns had an average daily sleep of 14.78 h on day 1 and 11.94 h on day 28, with a decrease throughout week 4 of life (p < 0.001). The decrease in daily sleeping time in the full–term groups, took place at the expense of the daylight span, where there was a decrease througout the first month of life (p < 0.01). There were no differences in preterm newborns during the light and dark phases. A progressive synchronization of sleep to the light–dark was seen in the control group. Therefore, the sleeping pattern could be taken as an indication of the degree of biological immaturity of preterm newborns.