January 12, 2016
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| Stress is a powerful precursor of fibromyalgia pain, but that pain does not lead to more stress. |
Stress is a powerful precursor of fibromyalgia pain, but that pain does not lead to more stress
Stress is a powerful precursor of fibromyalgia pain, but that pain does not lead to more stress, according to an ambulatory assessment study published in Psychoneuroendocrinology.1 (published site)
Using electronic diaries with 6 daily check-in times, researchers from the University of Marburg, Germany, followed stress and pain in the everyday lives of 32 women living with fibromyalgia.
Over a 2-week period, participants rated their momentary stress and pain on awakening, 30 minutes after awakening, and at 11 am, 2 pm, 6 pm, and 9 pm. Saliva samples collected at each diary entry were used to measure cortisol and alpha-amylase as indicators of stress-responsive systems.
Results showed that higher momentary stress correlated with increased pain levels 3 to 4 hours later, but that the reverse was untrue — momentary pain did not predict future stress. Moreover, the stress-pain relationship was not mediated by cortisol, nor by alpha-amylase.
According to coauthor Ricarda Mewes, PhD, the findings came as a "bit of a surprise."
"On the basis of the available cross-sectional literature and also on my experiences with patients suffering from chronic pain, I expected pain to result in stress in their everyday life," Dr Mewes toldClinical Pain Advisor, noting the possibility that pain could instead cause emotional distress, which was not addressed in the study.
Richard Harris, PhD, a researcher from the University of Michigan in Ann Arbor, has also used electronic diaries to examine the implications of pain fluctuation in fibromyalgia patients. Though not involved in the current study, DrHarris notes that inclusion of cortisol and alpha amylase provides an interesting aspect to this type of research.
"It is one of first [studies] that gets at this issue of the relationship between stress and pain, using ecological momentary assessment coupled with cortisol and other objective measures," Dr Harris told Clinical Pain Advisor, pointing out that real-time data is superior to that obtained via conventional diaries.
A Short-Lived Effect on Pain
Study participants were between the ages of 18 and 65 years (mean, 50.7 years), with a mean body mass index (BMI) of 25.2 kg/m2. On average, they had suffered widespread pain for 10.2 years, had pain in 11.6 of 19 potential sites, and rated their pain intensity as 8.2 on scale of 0 to 12.
Analysis of diary entries revealed that mean momentary stress levels varied from low (1.1 ± 0.9) to medium (1.7 ± 1.1) over the course of the day. Stress was lowest on awakening, and highest at 2 pm. In contrast, momentary pain was highest on awakening (50.1 ± 24.7), and lowest at 11 am (46.2 ± 26.3).
After controlling for sleep quality, physical activity, medications taken, and time since awakening, researchers found a positive association between momentary stress and concurrent pain (unstandardized coefficient [UC] = 4.11, P < .001), as well as pain 3 to 4 hours later (UC = 1.47, P<.001).
However, mean stress level did not predict next-day pain (UC = 0.59, P = .581).
When examining the association in the reverse, results showed that momentary pain failed to predict stress levels 3 to 4 hours later (UC < .01, P = .179).
"It is possible that [stress] might take some time to manifest," Dr Harris commented, noting that greater exposure to pain — 3 or more days of high pain — may be needed to achieve the effect.
"Pain is very much a neurobiological phenomenon, as is stress or the perception of stress. I think this study sets up potentially another line of investigation looking longitudinally at how stress might exacerbate pain at a later date," Dr Harris added.
No Role for Cortisol or Alpha-Amylase?
After controlling for sleep quality, physical activity, medications, and time after awakening, results showed that cortisol had a momentary impact on pain intensity (UC = 0.27, P = .009), that was reversed over time (UC < -0.01, P = .011). No relationship was found between momentary cortisol and stress (UC = -0.03, P = .846).
Alpha-amylase likewise was not found to mediate the effect of stress on pain (UC = -0.01, P = .195), after adjusting for sleep quality, physical activity, medications, and time of day.
According to Dr Harris, more research is needed to elucidate the neurobiological link between stress and pain — perhaps using serial magnetic resonance imaging (MRI) as a more direct approach to evaluate how the brain changes as symptoms vary.
Focus on Stress Management
According to Dr Mewes, the findings underscore the importance of stress management interventions for clinicians treating patients with fibromyalgia.
"Knowing what kind of stressors operate as pain-exacerbating factors in these patients would enable clinicians to specifically target dealing with these stressors. According to recent studies, this would imply focusing on the initiation and maintenance of positive social relationships to increase perceived social support," Dr Mewes said.
"It is of great importance to further explore the symptom-exacerbating effects of stress on a biological and psychological level, and to learn more about how persons with fibromyalgia can effectively cope with their stressors," Dr Mewes concluded.
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