Study data published in the Journal of Sleep Research outline the relationship between sleep disturbances, physical activity, and pain in patients with fibromyalgia. In a cohort of patients with fibromyalgia and insomnia, afternoon and early evening physical activity was associated with increased sleep disturbances. The relationship between physical activity and sleep patterns was particularly pronounced in individuals with greater self-reported pain.
Investigators extracted data from the baseline assessment of a clinical research trial assessing insomnia in fibromyalgia. The trial recruited adults with fibromyalgia from participating rheumatology and sleep clinics in Florida. Participants were considered to have insomnia if they reported >30 minutes of sleep-onset latency (SOL) or wake time after sleep onset (WASO) for ≥3 days/week for a duration of >6 months. Eligible participants also reported daytime dysfunction due to reported sleep disturbances.
The baseline assessment captured physical activity and sleep patterns using actigraphy. Patients wore Actiwatch-2 wrist watches configured to measure activity and photopic light for 14 consecutive days. Physical activity was reported as average activity per minute during 3 distinct time intervals: afternoon (12:00-3:00 p.m.), early evening (3:00-6:00 p.m.), and late evening (6:00-9:00 p.m.).
Patients were asked to rate their pain on a scale from 0 (no pain) to 100 (most intense pain) for each of the 14 days. Medication use for pain or sleep was also recorded daily. Multiple regression was performed to assess the relationship between physical activity, sleep difficulties, and pain.
The analytic cohort comprised 160 participants, among whom 150 (94%) were women. Mean age was 52.44 ± 11.73 years. In regression models, self-reported pain alone was not significantly associated with sleep outcomes. Instead, greater physical activity in the afternoon (12:00-3:00 p.m.) was associated with lower sleep efficiency, lower total sleep time, and higher WASO (all P <.001). Pain level was found to mediate these relationships as the association between sleep efficiency and physical activity intensified with greater pain. However, sleep efficiency was strongly related to afternoon physical activity at all pain levels (all P <.001).
Greater activity in the early evening (3:00-6:00 p.m.) was also independently associated with lower sleep efficiency, lower total sleep time, and higher WASO (all P <.001). As with the afternoon model, early evening activity was more strongly predictive of low sleep efficiency in those with high pain levels (P <.001). Physical activity remained associated with sleep efficiency in patients with average pain (P <.001). In patients with low pain, however, sleep efficiency was not significantly related to physical activity in the early evening (P =.06). Models which assessed late evening (6:00-9:00 p.m.) activity did not identify any significant associations with sleep outcomes.
Results from this study suggest that physical activity during the afternoon and early evening may cause sleep disturbances in patients with fibromyalgia and insomnia. This relationship was most pronounced in individuals with high pain levels. Late evening activity did not appear to impact sleep.
Study limitations include the small cohort size and lack of information on medication use and activity type.
“Prospective studies are needed to investigate…causal pathways between pre-bedtime objective activity, pain, medication usage and sleep outcomes in fibromyalgia,” the investigators wrote. “Specifically, studies examining whether increased afternoon and early evening physical activity exacerbates pain or induces pre-bedtime hyperarousal in fibromyalgia are warranted.”
McGovney KD, Curtis AF, McCrae CS. Associations between objective afternoon and evening physical activity and objective sleep in patients with fibromyalgia and insomnia [published online October 29, 2020]. J Sleep Res. doi: 10.1111/jsr.13220