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Associations between subjectively and objectively measured sleep duration and timing in infants at age 6 months.

STUDY OBJECTIVES
To compare estimates of sleep duration and timing from survey, diary and actigraphy in infants at age 6 months, overall and by select demographics and other factors.


METHODS
314 infants participating in the Rise & SHINE (Sleep Health in Infancy & Early Childhood study) cohort in Boston, MA, USA, wore an actigraph on their left ankle for 7 days. Parents concurrently completed a sleep diary and the expanded version of the Brief Infant Sleep Questionnaire. Concordance between subjective and objective sleep estimates was assessed using Bland-Altman plots, Spearman-rank correlations, intraclass correlations and linear regression models.


RESULTS
Mean infant age was 6.4 (0.6 SD) months; 51% were female and 42% were Non-Hispanic white. Mean total sleep duration using actigraphy was 526 (67 SD) minutes per night, 143 (42 SD) minutes per day, and 460 (100 SD) minutes during the longest nighttime sleep period. Relative to actigraphy, parent-completed survey and diary overestimated total day (by 29 and 31 minutes, respectively) and night sleep duration (67 and 43 minutes, respectively) and underestimated longest sleep (58 minutes), with highest agreement for sleep onset and offset timing (differences < 30 minutes). There was a tendency towards greater bias among short and long sleeping infants. Self-reporting bias for diary-measured longest nighttime sleep and total night sleep duration was higher in infants of parents reporting a problem with their baby's night awakenings and in low income families, respectively.


CONCLUSIONS
Our findings underscore the need to be cautious when comparing findings across studies using different sleep assessment methods.