Sleep patterns in childhood: a longitudinal assessment from the Generation XXI birth cohort.

OBJECTIVE: To describe sleep-wake patterns in young children, based on sleep characteristics in early infancy and preschool ages, identifying their main sociodemographic characteristics, and to assess the association between different sleep characteristics at both ages. METHOD: We included 1092 children from the Generation XXI birth cohort, evaluated at six months and four years of age, by face-to-face interviews. Sleep patterns were constructed through latent class analysis and structured equation modeling, including data on wake-up time and bedtime, afternoon naps, locale of nighttime sleep and night awakenings. To estimate the association between sociodemographic characteristics and sleep patterns, odds ratios and 95% confidence intervals were computed using logistic regression. RESULTS: Two sleep patterns were identified through latent class analysis: pattern 1 was characterized by earlier bedtime and wake-up times, while pattern 2 was defined by later times. When compared with pattern 1, pattern 2 was more frequent among children whose mothers had changed from partnered to not partnered until preschool age and those who did not stay at the kindergarten, and was less common among those with siblings. Through structured equation modeling, an aggregating factor was identified at preschool age, which was mainly correlated with bedtime and wake-up time. A positive association between sleep characteristics evaluated in early infancy and in preschool ages was observed. CONCLUSIONS: Sleep patterns and circadian sleep preferences seem to be developed early in life, which highlight the importance of promoting an adequate sleep hygiene from infancy, assuming its impact on sleep quality during the life course.