Actigraphy scoring reliability in the study of osteoporotic fractures

Study Objectives: The editing and scoring of actigraphy data are important for calculating variables that describe sleep. Scoring is dependent on marking time points for when a participant got in and out of bed, plus time when the actigraph was removed. This placement of time points is subject to error. We examined interscorer reliability to determine if files scored by 2 different people were comparable. Design: Observational study. Setting: Community-based. Participants: A subset of 36 women taken from the latest biannual visit of the Study of Osteoporotic Fractures. All women had actigraphy data scored by 1 scorer for the Study of Osteoporotic Fractures staff, plus a blinded rescoring by an expert scorer at a different site. Interventions: N/A. Measurements and Results: The outcomes of interest from actigraphy are duration of in-bed interval, total sleep time, sleep latency, sleep efficiency, wake after sleep onset, total nap time, and total daytime minutes of watch removal. Clearly documented actigraphy scoring procedures were used. There were no significant differences between the expert scorer and the study scorer in sleep outcomes (all P values >.16 from a paired t test). There was a small but statistically significant difference between scorers for watch removal times (mean absolute difference 3.4 minutes 5.4, P=.02). The intraclass correlation coefficients showed a high level of agreement (range, 0.84-0.99). Conclusions: Even in a large study with 2 scorers, it is possible to use actigraphy as a measure of sleep without introducing interscorer measurement error. Using well-documented scoring and data-gathering procedures are essential for data quality control.