Information on Bedtimes and Wake Times Improves the Relation Between Self-Reported and Objective Assessments of Sleep in Adults

Abstract

Study objectives: To investigate the correlation between self-reported and objective measures of total sleep time (TST) in adults and examine whether sex, race/ethnicity, and weight status influence this association.

Methods: Participants were individuals who screened for sleep intervention studies, providing > 7 days of wrist actigraphy sleep data (TSTobj) and reporting sleep duration (TSTPSQI) using the Pittsburgh Sleep Quality Index (PSQI) questionnaire (n = 53 men, 60 women; 59% minority/Hispanics; age 30.9 ± 9.7 years; body mass index 26.2 ± 3.2 kg/m2). In addition, TSTbed/wake was calculated as the difference between bedtime and waketime, minus the time to fall asleep, from the PSQI. Univariate regression analyses were performed to assess the relation between TSTobj and TSTPSQI and TSTbed/wake and compare the relation by sex, race, and ethnicity. Bland-Altman tests were done to assess bias by sex, race/ethnicity, weight status, and sleep quality.

Results: TSTbed/wake correlated with TSTobj (r = .57, P < .0001). TSTPSQI and TSTbed/wake were greater than TSTobj (0.63 ± 0.99 hours and 0.79 ± 0.76 hours, respectively, both P < .0001). The difference between TSTPSQI and TSTobj did not vary by sex (β = .12, P = .52), race/ethnicity (β = .15, P = .48), age (β = -.01, P = .27), or body mass index (β = .04, P = .13) whereas that between TSTbed/wake and TSTobj varied by age (β = -.020, P = .0051), BMI (β = .054, P = .0021), race/ethnicity (β = .36, P = .021), and sleep efficiency (β = -.089, P < .0001).

Conclusions: Calculating TST using self-reported bedtimes and wake times provided TST estimate that correlated with TSTobj but greater over-reporting occurred in younger and heavier individuals, non-whites or Hispanics, and those with low sleep efficiency. In clinical and research settings, asking individuals to report bedtimes, wake times, and length of time to fall asleep may more accurately estimate TST than asking about sleep duration alone.

Keywords: Pittsburg Sleep Quality Index; actigraphy; sleep duration; subjective sleep.

Copyright © 2019 American Academy of Sleep Medicine. All rights reserved.

Figures

Figure 1. Fit plot for the difference between TSTobj and TSTPSQI.

Fit plot for the difference between TSTobj and TSTPSQI as a function of (A) sleep efficiency and (B) global PSQI score. PSQI = Pittsburgh Sleep Quality Index, TSTobj = total sleep time by actigraphy, TSTPSQI = total sleep time by PSQI.

Figure 2. Lin concordance correlation coefficient between TSTobj and TSTbed/wake and TSTPSQI.

Lin concordance correlation coefficient between TSTobj and TSTbed/wake (A) and TSTobj and TSTPSQI(B). The line represents perfect concordance. Each data point is represented by an asterisk. PSQI = Pittsburgh Sleep Quality Index, TSTbed/wake = calculated total sleep time from PSQI bedtime, wake time, and time to fall asleep, TSTobj = total sleep time by actigraphy, TSTPSQI = total sleep time by PSQI.

Figure 3. Fit plot for the difference between TSTobj and TSTbed/wake.

Fit plot for the difference between TSTobj and TSTbed/wake as a function of (A) sleep efficiency, (B) global PSQI score, and (C) BMI. BMI = body mass index, PSQI = Pittsburgh Sleep Quality Index, TSTbed/wake = calculated total sleep time from PSQI bedtime, wake time, and time to fall asleep, TSTobj = total sleep time by actigraphy.