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).