Patients with fibromyalgia (FM) who reported more nonrestorative sleep reported higher levels of activity interference the next morning, according to a study published in the Journal of Pain.

Although there is a recognized association in FM between nonrestorative sleep, which is a hallmark of the disorder, and activity interference, the mechanisms underlying this relationship remain unclear.

In this secondary analysis of a randomized clinical trial in which 220 patients with FM were enrolled between 2008 and 2013 (ages, 18-72 years; mean age, 51.25 years; 87.0% women; 78.0% white), participants were asked to fill out health questionnaire packets as well as diaries 4 times per day during the next 21 days, using a mobile phone (early morning, 11 am, 4 pm, and bedtime). In the early morning call, respondents were asked to rate their previous night’s sleep quality on a 0 to 100 scale; during the 11 am call, they were asked to rate their levels of morning pain catastrophizing, using a 1 to 5 scale; during the 4 pm call, they were asked to rate their average recent pain level on a 0 to 100 scale; and during the end-of-day call, they were asked to rate several aspects of physical function using a 1 to 3 (no, maybe, yes) scale.

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There was an 82% overall completion rate on the daily diaries, with patients reporting moderate levels of nonrestorative sleep, morning catastrophizing, afternoon pain severity, and end-of-day activity interference. Intraclass correlation coefficients ranged from 0.30 for nonrestorative sleep to 0.51 for pain severity, with significant correlations in predicted directions.

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Although higher levels of nonrestorative sleep during the previous night were associated with greater morning pain catastrophizing (P <.001), poor sleep was not found to predict afternoon pain severity after controlling for catastrophizing (P =.12). When controlling for nonrestorative sleep and morning pain severity, increased morning pain catastrophizing was found to correlate with afternoon pain severity (P <.001) and with later activity interference, independent of nonrestorative sleep and afternoon severity (P <.001). Greater afternoon pain severity predicted higher levels of end-of-day activity interference, independent of prior nonrestorative sleep or morning catastrophizing (P <.001). Finally, after controlling for morning catastrophizing and afternoon severity, nonrestorative sleep was a found to be a predictor of end-of-day activity interference (P <.01).

The hypothesized 3-path sequential mediation, in which prior nonrestorative sleep was associated with morning catastrophizing, which increased afternoon pain severity, which resulted in late day activity interference, was confirmed in the joint significance test.

Study strengths include a thorough examination of the intraday process model, a large sample size, solid statistical methodologies, multiple daily assessments, and good diary completion rates.

Study limitations include the sole assessment of nonrestorative sleep, the assessment of catastrophizing using a single diary item, small overall effect sizes, and possible effect of early morning symptoms on sleep quality reporting.

“An intervention that targets attenuating non-restorative sleep and pain catastrophizing may help improve daily physical functioning of this population,” noted the authors.

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Mun CJ, Davis MC, Campbell C, Finan P, Tennen H. Linking non-restorative sleep and activity interference through pain catastrophizing and pain severity: An intra-day process model among individuals with fibromyalgia [published online September 14, 2019]. J Pain. doi:10.1016/j.jpain.2019.09.001