Introduction: Fibromyalgia involves chronic pain and disrupted physical activity and sleep. Research examining the relationship between pre-bedtime physical activity, pain, and objective sleep is limited. This study examined whether objectively measured physical activity levels (via actigraphy), pain intensity, or their interaction are associated with polysomnographic sleep outcomes.
Methods: Adults with fibromyalgia and insomnia complaints (n = 134, mean age = 52 yrs, SD = 12 yrs, 94% female) completed 14 days of biaxial, wrist worn actigraphy, pain ratings, and a single night of polysomnography (PSG). Average activity for intervals 9:00-12:00, 12:00-15:00, 15:00-18:00, 18:00-21:00 was computed. Multiple regressions examined whether average activity, average evening pain, or their interaction were associated with PSG outcomes: sleep onset latency (SOL), wake after sleep onset (WASO), sleep efficiency, %stage1, %stage2, %stage3, and %rapid eye movement. Analyses controlled for age, body mass index, average bedtime, time in bed, and sleep/pain medication use.
Results: Greater morning actigraphic physical activity from 9:00 to 12:00 was independently associated with greater %stage 1 sleep (B = 0.01, SE = 0.00, p < .01). Greater afternoon activity from 12:00 to 15:00 independently predicted a higher WASO (p < .001). Associations between afternoon physical activity from 12:00 to 15:00 and greater %stage 1 (p < .001) were significant for at higher (~71/100), average (~52/100), but not lowest (~32/100) pain.
Conclusion: Greater morning and afternoon activity is associated with greater PSG sleep fragmentation and greater %stage 1 sleep in individuals with fibromyalgia and insomnia complaints, and the relationship between higher physical activity and greater %stage 1 is stronger for individuals with higher pain. Further studies examining causal pathways between physical activity, activity pacing, and sleep are warranted in fibromyalgia.
Trial registration: ClinicalTrials.gov NCT02001077.