Factors Related to the Sleep Duration of 3-Month-Old Infants.

To identify the factors related to sleep duration in 3-month-old infants.  From 2021 to 2023, we conducted a cross-sectional study in the city of Araraquara, Brazil, involving 140 mothers and their respective 3-month-old infants. Maternal socioeconomic, demographic, obstetric, and nutritional characteristics, as well as nutritional and morbidity characteristics of the respective infants, were evaluated. Sleep duration was determined by the Brief Infant Sleep Questionnaire (BISQ). Multivariate linear regression analysis was used to assess the associations of maternal, newborn, and infant factors with sleep duration at three months.  The nighttime sleep duration of the infants was of 9 hours. There were negative associations between nighttime sleep duration and prone sleep position (  = 0.011), falling asleep between 8:30 pm and 11:00 pm (  = 0.032), falling asleep after 11:00 pm (  < 0.001), respiratory infection (  = 0.011), dermatitis (  = 0.002), and the presence of children under 9 years of age in the household (  = 0.013).  In the present study, factors such as infant morbidity, the presence of other children in the household, and sleeping habits were associated with a decrease in sleep duration in 3-month-old infants. Therefore, we emphasize the importance of early diagnosis of morbidity in the first months of life and of promoting healthy habits such as regulating the time to go to sleep, providing an adequate sleep environment, and other practices that help improve the quality and duration of sleep.