Do pregnant women accurately report sleep time? A comparison between self-reported and objective measures of sleep duration in pregnancy among a sample of urban mothers.

PURPOSE: Survey questions are commonly used to assess sleep duration because of their low cost and convenience. Responses to these questions correlate moderately with objectively measured sleep duration in nonpregnant individuals, but little is known about the validity of self-reported sleep measures in pregnancy. The aim of the present study was to determine the extent to which self-reported gestational sleep duration assessed by questionnaire predicted objectively measured gestational sleep duration via actigraphy.
METHODS: We analyzed data from 80 mothers enrolled in an ancillary study of Project BABIES, a prospective cohort study of urban, pregnant women. Sleep measurements were collected in midpregnancy and included 7 days of wrist actigraphy, a sleep log, and survey questions about sleep time adapted from the Pittsburgh Sleep Quality Index.
RESULTS: Mean measured gestational sleep duration derived from actigraphy was 6.87 h [standard deviation (SD) 0.87], and questionnaire-assessed nocturnal sleep time averaged 7.29 h (SD 1.84). While the difference between measures did not reach statistical significance (p = 0.07 for paired samples t test), over half (62 %) of participants reported a habitual average nightly sleep time that differed more than 1 h from their average actigraphically measured sleep duration (39 % overestimated by more than an hour; 23 % underestimated by more than an hour). There was no correlation between measures (r = 0.007; 95 % confidence interval -0.21, 0.23).
CONCLUSION: Questionnaire-derived reports of usual sleep hours do not reflect objectively measured sleep time in urban, pregnant women. Actigraphy is preferable to accurately assess gestational sleep duration.