Longitudinal assessment of leg motor activity and sleep patterns in infants with and without Down syndrome

Whether infants with Down syndrome (DS) perform leg movements with the same frequency and quality as their typical development (TD) counterparts is equivocal. Furthermore, the relationship between these early leg movements and later onset of locomotor milestones has only been partially explored. The aims of this study were two-fold: (1) to describe the longitudinal leg activity in infants with and without DS (3–6 months), and (2) to examine sleeping patterns and leg activity during the night. In addition, the relationships between leg activities and sleep patterns with locomotor development were explored. An activity monitor was placed monthly on the infant's ankle for 48 h. Data were analyzed to separate day–night, high–low activity, and sleep fragmentation. The results indicate that infants with DS produced more low intensity activity and more fragmented sleep. These findings are discussed in relation to the influence of early motor activity on achievement of functional motor behavior.