The study, authored by Michael D. Nevarez, of Harvard Medical School, focused on 1,676 mother-infant pairs, where the mothers reported their infants’ average 24-hour sleep duration at six months. Also examined were daytime nap and nighttime sleep duration separately.

According to the results, infants’ mean sleep duration at six months, including daytime naps and nighttime sleep, was 12.2 hours per day. Less household income and lower maternal education were associated with shorter infant sleep duration. Compared with Caucasian infants, African-American infants slept 0.94 fewer total hours per day. Also, African-American, Hispanic, and Asian infants slept more hours during daytime naps but fewer hours at night. Infants whose mothers had a history of depression during pregnancy and those who were being breast-fed at six months appeared to sleep fewer total hours per day.

“Previous studies have shown links between sleep loss in children and its potential negative effects on health outcomes, such as overweight status and cognitive development,” said Nevarez. “Given this adverse relationship, we felt that it was critical to explore factors that may influence the sleep of children at much younger ages, namely within the first six months of life. As any parent knows, an infant's sleep can seem anything but predictable during this period, yet, our study observed a number of notable associations. Perhaps most striking were the relationships between infants’ sleep and their socioeconomic and racial/ethnic backgrounds. As with other complex pediatric conditions such as obesity, the amount of sleep children obtain, even during infancy, may have larger socioeconomic and cultural contexts that warrant consideration.”-American Academy of Sleep Medicine