Chemical and Physical Correlates to Pain

Abstract

The accurate measurement of pain is important to physicians for medical decision making. Pain is considered to be the largest health-related burden to society as well as the leading cause of long-term disability worldwide. The goal of this study was to give health care providers a more objective way to assess pain presence and intensity, and thus allow for more effective patient interventions. The Visual Analog Scale (VAS) was used to assess pain intensity. This study focused on acute, nociceptive pain and its relation to a combined salivary alpha amylase (sAA), salivary cortisol (sC), and total protein count metric. Since other studies have shown high correlations between sAA and pain intensity, sAA is also excreted in response to stress, and sC responds to stress but not pain, the hypothesis was that a combined metric ((sAA/100 + sC) /Total Protein) would render an even higher correlation with acute nociceptive pain. A total of 24 participants were recruited for this study, with 14 being experimental (in pain) and 10 being controls (no pain). The data were analyzed using linear regression analysis. There was no discernable correlation between sAA and pain ranging from 0-10 (r=0.250,p=0.288) and no correlation between (sAA/100 + sC) /Total Protein and pain intensity for pain 0-10 (r=-0.049,p=0.838). This study, because of the available literature, was built on the assumption that sAA already correlated moderately with pain intensity, but the data do not support this assumption. Due to how weak the relationship was with the originally-hypothesized metric, the data were analyzed to derive a better combined metric. Multiple metrics, utilizing salivary alpha amylase, salivary cortisol, and total protein count were analyzed. None of the metrics involving total protein produced statistically significant results. One metric, which combined portions of salivary alpha amylase with portions of salivary cortisol readings, (sAA-14*sC)^0.6, showed promising results. The correlation between (sAA-14*sC)^0.6 and pain intensity for pain 0-10 (r=0.287,p=0.157) was nonexistent, but also not statistically significant. When the focus is narrowed to pain ranging from 0-6 (no pain to moderate pain), the correlation between sAA and pain becomes high (r=0.761,p<0.001). In the 0-6 range, (sAA-14*sC)^0.6 shows an even higher correlation than sAA alone (r=0.787,p<0.001). A high correlation (r=0.700,p<0.05) was noted when the age range was narrowed to participants under the age of 65 for pain 0-6. Even though 0-6 only covers no pain, mild pain, and moderate pain, differences on the lower end (such as a 3 being reduced to a 2) still translate into large percentage reductions in pain, leading to higher quality of life. This led to the conclusion that (sAA-14*sC)^0.6, utilizing whole, unstimulated saliva, may be a viable method for research aimed at quantifiably measuring pain in participants, especially those who are experiencing pain between 0 and 6 (0 and 60 mm on the VAS).