Light is beneficial for infant circadian entrainment: an actigraphic study

This article is a report of an exploratory study of the relation between light exposure and circadian rest-activity patterns in infants.

Ambient light is a major environmental stimulus for regulation of circadian rhythm of sleep and wake in adults, but few studies have been conducted to examine environmental light exposure in relation to rest-activity circadian rhythm parameters of infants.

An intensive within-subject design was used with a convenience sample of 22 infants (mean postnatal age 49·8 days) who wore a combined light and activity monitoring device for seven consecutive days at home. For each infant, light data (lux) were aggregated over the 7 days into categories of illumination and expressed in mean minutes/day. Circadian light and activity parameters, including mesor, amplitude, acrophase and R(2) cosinor fit, were determined using cosinor analysis. Associations between light exposure and circadian rest-activity rhythm parameters were examined using correlation and regression analyses. Data were collected between 2006 and 2007.

Infants spent only one-eighth of their daytime hours in an environment with >100 lux light level. There was a relatively large statistically significant relation between the acrophase of light exposure and the acrophase of activity. Increased duration of daily exposure to >100 lux of illumination, and increased amplitude of circadian rhythm of light were associated with stronger circadian patterns of infant activity.

Results suggest an association between light and activity patterns and that increasing duration of exposure to moderate light levels may be a simple and economical nursing intervention during the early postnatal weeks.