In November 2018 researchers from the USA published the results of their study to assess the association between sleep discrepancy, its night-to-night variability and firbromyalgia symptoms. 223 adults with fibromyalgia and insomnia (average age 52 years; 93% women) kept a sleep diary for 14 days and in addition wore a small device to monitor durations of resting and activity. Sleep discrepancy was calculated by subtracting diary estimates from device estimates for each night in the following sleep parameters: delay in sleep onset, wake-after-sleep onset and total sleep time. In addition, the individuals recorded their mood, pain, fatigue, sleep/pain medications, nap duration, and caffeine consumption. Results showed that whilst average sleep discrepancies were small for all sleep parameters, ie under 10 minutes, sleep discrepancy for any one night appeared large, ie greater than 30 minutes. A further analysis revealed that greater morning pain appeared to be associated with greater awake time after falling asleep during the previous night. In addition, taking prescribed pain medications also appeared to be associated with greater night-to-night variability in waking after falling sleep as well as total sleep time. Future research is required to investigate these findings further.
Chan WS et al. Sleep Discrepancy in Patients With Comorbid Fibromyalgia and Insomnia: Demographic, Behavioral, and Clinical Correlates. J Sleep Med 2018 Nov 15;14(11):1911-1919.