Environmental light exposure, rest-activity rhythms, and symptoms of inattention and hyperactivity: An observational study of Australian preschoolers

Environmental light increases acute alertness and is the main regulator of the circadian clock in humans. In turn, circadian processes are strongly associated with inattention and hyperactivity symptoms in both children and adults. Evidence from animal studies suggest that light exposure may affect inattention and hyperactivity related behaviors during critical windows in early development. However, very little is known about the associations between light exposure, rest-activity rhythms and symptoms of inattention and hyperactivity in young children. Our aim was to examine whether the stability in rest-activity rhythms and the dosage, intensity and duration of environmental light were associated with symptoms of inattention and hyperactivity in children between 3 and 6 years of age. The present study used a subsample of the E4Kids Study. Objective measures of light exposure and stability of rest-activity rhythms were collected from 48 preschool children continuously over a period of two weeks. Parental reports of inattention and hyperactivity symptoms were collected concurrently and again 12 months later. Longer durations of light exposure were strongly associated with lower levels of hyperactivity symptoms at baseline (b = −0.64, CI = −0.97; −0.25), but not at follow up. The stability of rest-activity rhythms was associated with hyperactivity symptoms at follow up (b = −0.44, −0.81; −0.08), but not at baseline. Neither the stability of rest-activity rhythms or light exposure were associated with inattention symptoms. We provide the first evidence that the duration and intensity of environmental light exposure is inversely and strongly associated with symptoms of hyperactivity in young children in a naturalistic setting. Potential mechanistic pathways are discussed.