Longitudinal changes in sleep patterns and circadian rhythm metrics in preschool-age children from Northern Mexico

Abstract

ObjectivesTo assess changes in sleep parameters and circadian rhythm metrics measured by actigraphy in preschool-aged children. DesignLongitudinal analysis over 1 year. ParticipantsNinety-four children living in Tijuana and Ensenada, Mexico. MeasurementsChildren wore accelerometers on the right hip for one continuous week at baseline and 1-year follow-up. Parents recorded child bedtime, waketime, and naps in sleep diaries. We used cosinor and nonparametric approaches to calculate circadian rhythm metrics. ResultsAt baseline, children had a mean age of 4.2 years, and 51.1% were girls. In multivariable models adjusted for age, gender, BMI category, parental education, household income and city, at follow-up children had significantly earlier waketimes (β = -7.99 minutes, p < .001) compared to baseline. Children also had lower sleep onset latency (β = -2.32 minutes, p = .057), and longer nighttime sleep (β = 9.38 minutes, p = .079), but these changes were not significant at the α < 0.05 level. We found significant increases in log relative amplitude (β = 0.017, p = .009), and decreases in log midline estimated statistic of rhythm (β = -0.084, p = .017) and log of the least active 5-hour period (β = -0.057, p = .010). When we adjusted for co-sleeping, we found significant decreases in the number of nighttime awakenings (β = -1.29, p = .011) but otherwise similar results. There were no other changes in sleep parameters or circadian rhythm metrics. ConclusionsMean increases in nighttime sleep and earlier wake times over one year were concomitant with decreases in overall activity levels and increases in circadian rhythm robustness. Co-sleeping was a predictor of sleep disturbances. This study provides longitudinal evidence regarding changes in sleep and circadian metrics in a sample of children from an under-researched sociodemographic group during an important, early life period.