Reproducibility of a Standardized Actigraphy Scoring Algorithm for Sleep in a US Hispanic/Latino Population

Abstract

Study objectives: While actigraphy is considered objective, the process of setting rest intervals to calculate sleep variables is subjective. We sought to evaluate the reproducibility of actigraphy-derived measures of sleep using a standardized algorithm for setting rest intervals.

Design: Observational study.

Setting: Community-based.

Participants: A random sample of 50 adults aged 18-64 years free of severe sleep apnea participating in the Sueño sleep ancillary study to the Hispanic Community Health Study/Study of Latinos.

Interventions: N/A.

Measurements and results: Participants underwent 7 days of continuous wrist actigraphy and completed daily sleep diaries. Studies were scored twice by each of two scorers. Rest intervals were set using a standardized hierarchical approach based on event marker, diary, light, and activity data. Sleep/wake status was then determined for each 30-sec epoch using a validated algorithm, and this was used to generate 11 variables: mean nightly sleep duration, nap duration, 24-h sleep duration, sleep latency, sleep maintenance efficiency, sleep fragmentation index, sleep onset time, sleep offset time, sleep midpoint time, standard deviation of sleep duration, and standard deviation of sleep midpoint. Intra-scorer intraclass correlation coefficients (ICCs) were high, ranging from 0.911 to 0.995 across all 11 variables. Similarly, inter-scorer ICCs were high, also ranging from 0.911 to 0.995, and mean inter-scorer differences were small. Bland-Altman plots did not reveal any systematic disagreement in scoring.

Conclusions: With use of a standardized algorithm to set rest intervals, scoring of actigraphy for the purpose of generating a wide array of sleep variables is highly reproducible.

Keywords: Hispanic; actigraphy; reproducibility; sleep.

Figure 1

Inter-scorer differences in actigraphic variables, the Sueño Reproducibility Study (n = 50). Bland and Altman plots assessing the difference between scorers (averaging over passes by each scorer) as a function of the overall mean value for nightly sleep duration (A), napping duration (B), 24-h sleep duration (C), standard deviation of nightly sleep duration (D), sleep latency (E), sleep maintenance efficiency (F), sleep fragmentation index (G), sleep onset time (H), sleep offset time (I), sleep midpoint time (J), and standard deviation of sleep midpoint time (K). For each graph, the mean difference and 95% confidence interval lines are plotted along with the raw data. SD, standard deviation.