The current study compares sleep variables obtained from videosomnography, actigraphy, and sleep diaries, three of the most common sleep assessment methods used in infant sleep studies. Using a sample of 90 African American 3-month olds, we compare correlations and discrepancies for seven sleep variables across each of the three pairs of assessment methods for one night of a week-long sleep study. These seven variables are indicative of sleep schedule (e.g. sleep onset time, rise time), duration (e.g. sleep period, sleep time, wake time), and fragmentation (e.g. night wakings, longest sleep period). We find that across all sleep assessment methods, correlations are highest for variables indicative of sleep schedule, and lowest for variables indicative of sleep fragmentation. Comparing the magnitude and significance of the discrepancies, we find that actigraphy and sleep diaries significantly overestimate sleep period duration and underestimate the number of night waking episodes, compared with videosomnography. Actigraphy and sleep diaries were more concordant with one another than with videosomnography. Epoch-by-epoch analyses indicated that actigraphy had low sensitivity to detect wakefulness, compared with videosomnography. Contrary to our hypothesis, the discrepancies between sleep assessment methods did not vary widely based on infant sleep location (own room vs. parent's room) or sleep surface (own bed vs. parent's bed). Limitations and implications of these findings for future research are discussed.
Statement of Significance
Scientists across many disciplines are increasingly interested in incorporating measures of infant sleep into their research studies. However, it is currently unclear what the best methods are for measuring infant sleep, or how the available methods compare to one another. The current study quantitatively compares indicators of infant sleep schedule, duration, and fragmentation across three common assessment methods: videosomnography, actigraphy, and sleep diaries. We found significant discrepancies across all pairs of sleep methods. The magnitude of these discrepancies did not vary by infant sleep location or sleep surface. We conclude that these three methods of sleep assessment are not interchangeable. Researchers must take care to choose their assessment methods and interpret their findings in light of these demonstrated differences.