Relations between 24-h movement behaviors, declarative memory, and hippocampal volume in early childhood.

This study aimed to determine if 24-h movement behaviors (sedentary time, physical activity, and sleep), considered independently and together, were associated with declarative memory and hippocampal volume in late early childhood. Observational data were obtained from preschool-aged children (timepoint 1: n = 35 children, 3.9 ± 0.5 years; 6 months later: n = 28 children, 4.5 ± 0.5 years). Movement behaviors were measured with actigraphy. Outcomes were declarative memory and hippocampal subregion volumes. Multilevel models explored movement behaviors independently as absolute values, and with both absolute total activity, 24-h sleep duration, and night sleep efficiency. Movement behaviors were also explored as compositions in linear regression models. In independent models, sleep duration and moderate to vigorous physical activity were positively associated with total and right hippocampal volumes, respectively. When examined together, children meeting sleep recommendations were more likely to have larger total, right and left hemisphere, body, and tail hippocampal volumes. In our sample of preschool children, we observed positive associations between sleep duration and hippocampal volume, independent of age. To improve our understanding of the connections between 24-h behaviors and brain health in early childhood, larger samples that also consider the context and subcomponents of movement behaviors may be warranted.