Home is where sleep is: an ecological approach to test the validity of actigraphy for the assessment of insomnia.

STUDY OBJECTIVES: This study tested the ecological validity of actigraphy (ACT) for estimating objective sleep parameters in participants' homes. We also examined how well ACT and polysomnography (PSG) measures discriminated (1) individuals with and without insomnia; and (2) nights participants rated worse, the same as, or better than average.

METHODS: Thirty-one primary insomnia sufferers and 31 normal sleepers completed up to 3 consecutive monitoring nights with wrist ACT and PSG in their homes. They also rated how each night compared to their "average night's" sleep. ACT and PSG measures of sleep onset latency (SOL), wake after sleep onset (WASO), total sleep time (TST), and sleep efficiency (SE) were then compared using Bland and Altman correlational procedures and repeated measures ANOVAs. Differences between groups and among nights assigned distinctive ratings were tested via mixed-model ANOVAs.

RESULTS: Medium to large between- and within-subject correlations were observed for all measures in the insomnia sufferers sample and for most measures in the normal sleepers sample. Two (ACT vs. PSG) x 3 (nights) repeated measures ANOVAs showed that, in both samples, SOL derived from ACT was consistently lower than SOL derived from PSG across the 3 nights of recording. By contrast, ACT and PSG produced estimates of WASO, TST, and SE that did not differ from each other across nights. Subsequent 2 (insomnia vs. normal sleeper) x 3 (worse, same, better than average) mixed-model ANOVAs showed only ACT SOL discriminated those with and without insomnia and nights assigned distinctive ratings. Among the PSG-derived measures, only SE showed such a pattern.

CONCLUSIONS: ACT provides informative data for insomnia sufferers and normal sleepers in their usual sleep environments. The ACT estimate of SOL seems sensitive to night-to-night differences in subjective sleep ratings. A possible strength of ACT lies in its assessment of nocturnal movement, a parameter different from PSG-based sleep measures.