Nightly analyses of subjective and objective (actigraphy) measures of sleep in fibromyalgia syndrome: what accounts for the discrepancy?

OBJECTIVES: To evaluate the concordance between the subjective and objective methods of sleep assessment in patients with fibromyalgia syndrome (FMS) and to delineate factors associated with discrepancy between the 2 sleep assessment methods.
METHODS: Seventy-five patients with FMS completed a 7-day home assessment protocol. They wore an actigraphic device at all times. In the morning, they used the electronic diary to record the subjective report of sleep from the previous night and current severity of the FMS-related symptoms.
RESULTS: On average, the 2 assessment methods yielded a 73 absolute minute difference per night per patient. About half of the nights, sleep duration was underestimated. Approximately 20% of the nights had greater than 2-hour difference between the 2 methods. Factors related to this large discrepancy were (1) objective indicator of restless sleep, (2) subjective report of difficulty falling asleep, and (3) report of fatigue at the time of reporting. FMS-related symptoms were related to subjective report of poor sleep but not to objective sleep data. DISCUSSION: Misestimation of sleep seems common in FMS patients, particularly when their sleep quality is poor. Careful considerations for evaluating the severity of patients' sleep complaints are critical in adequate management of sleep disturbance that is commonly reported by FMS patients.