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Vitamin D deficiency as a mediator of ethnic differences in experimental pain: preliminary findings
Abstracts (140) The burden of chronic lower back pain with neuropathic components: a healthcare resource perspective M Mehra, K Hill, D Nicholl, and J Schadrack; Johnson & Johnson Pharmaceutical Services, Raritan, NJ Little evidence exists on the medical care and costs for patients with chronic lower back pain (CLBP) with neuropathic components. This research addresses the need for population-based studies to examine healthcare service use and costs for CLBP patients with and without neuropathic components in the general US population. Data were analyzed from PharMetrics IMS LifeLinkTM US Claims Database 2006-2008. Patients >18 years, with 36 months continuous enrollment, ICD 9 code for low back pain and claims in 3 out of 4 consecutive months in the 12-month prospective period were included and classified as chronic low back pain (CLBP). Patients were further classified as CLBP with neuropathic component (wNP) and those without a neuropathic component (woNP) based on ICD 9 codes. Hospitalization, emergency room (ER) visits, diagnostic, minimally invasive and major procedures, physical therapy, prescription medication use and associated costs were assessed for period 1 January 2008 to 31 December 2008. 39,425 patients were identified with CLBP; 90.4% wNP. Patients wNP were slightly older, with a higher proportion of women and clinically diagnosed depression. A significantly higher proportion of CLBP patients wNP used: any prescription medication at index event, opioids (particularly Schedule II) and healthcare resources (hospitalizations, ER, diagnostics, minimally invasive and major procedures). Total direct medical costs of CLBP related resource use were approximately $96 million over 12 month follow-up. CLBP wNP accounted for 96% of total costs. Mean annual cost of care per patient for CLBP wNP is approximately 140% higher than those with CLBP woNP ($2,426 vs. $1,007). The disproportionately high share of interventional resource use in CLBP wNP suggests greater need for new treatment options that more comprehensively manage the range of pain symptoms and signaling mechanisms involved to help improve patient outcomes and reduce the economic burden on health care systems.
(141) A pain in the neck? Which regions of body pain are most associated with pain interference and other health outcomes 6 weeks after motor vehicle collision K Whittington, A Bortsov, A Soward, J Jones, D Peak, R Swor, D Lee, N Rathlev, R Domeier, P Hendry, W Maixner, G Slade, and S McLean; University of North Carolina , Chapel Hill, NC Traditionally, studies examining persistent post-motor vehicle collision (MVC) pain have focused on the neck region (Whiplash-Associated Disorders), however several recent studies have demonstrated that persistent post-MVC pain is not limited to the neck region. We assessed which regions of body pain are most associated with pain interference and other health outcomes 6 weeks after MVC using data from a prospective, multisite, longitudinal study of patients (n = 427) enrolled in the emergency department after MVC. Among patients reporting persistent post-MVC pain in one or more body regions 6 weeks after MVC (n = 321), we examined the strength of association (assessed via unstandardized beta regression coefficient) between pain severity (0-10 numeric rating scale) in each body region (Regional Pain Scale) and MVC-related pain interference (Brief Pain Inventory subscales) and other health outcomes: post-traumatic stress disorder (PTSD) symptoms (Impact of Events Scale-Revised), depressive symptoms (Center for Epidemiological Studies Depression Scale), and mental and physical health (Short Form 12 Health Survey MCS, PCS). For each outcome, pain regions were then ranked according to strength of association, and mean rankings across pain interference subscales were calculated. Pain in the neck region had the highest mean ranking across pain interference subscales 6 weeks after MVC, followed by pain in the abdomen, upper back, head, and lower back regions. Pain in the neck region was also most strongly associated with depressive symptoms, physical health, and mental health. Pain in the abdominal region was the next most strongly associated with these three outcomes, and was the pain region most strongly associated with comorbid PTSD symptoms. These findings broadly support an emphasis on the neck region when examining post-MVC pain outcomes, while highlighting the important influence of pain in a number of body regions on pain interference and emotional and physical health outcomes. Funded by NIH 1R01AR056328.
The Journal of Pain
P11
A09 Prediction of Outcome (142) Experimental pain sensitivity does not differ three months after surgery in patients with high and low clinical pain intensity C Valencia, R Fillingim, and S George; University of Florida, Gainesville, FL The transition to a chronic pain state could be influenced by neuroplastic changes in the central nervous system (CNS) induced by surgery. Conditioned pain modulation (CPM), temporal summation (TS), and hyperalgesia have been linked to the development of chronic pain, but have not been widely studied in post-operative models. The purposes of this study were to investigate: 1) baseline differences in CPM, TS and pain threshold between patients having shoulder surgery and healthy controls, and 2) whether CPM, TS and pain threshold differentially change over time between patients with high and low clinical pain. TS was generated with repeated thermal stimuli, CPM was assessed using TS as the experimental stimulus and cold water bath as the conditioning stimulus, and threshold was assessed with thermal stimuli. Three months after surgery patients were classified by the Brief Pain Inventory (BPI) into high and low clinical pain intensity groups. There were no baseline differences on CPM, TS, and threshold among the 3 groups (2 patient groups and age, sex matched controls). Furthermore, there were no differential changes for CPM, TS or threshold between the high and low clinical pain groups. The results of the present study revealed that for this surgical model there was no evidence of: 1) enhanced CNS processing of pain at baseline, and 2) changes in CNS processing during 3 month post-operative period. These results suggest that 3 months may not be a sufficient time period to reveal neuroplastic changes in the CNS, or that development of chronic pain may occur through different pathways for this patient population. Grant #AR055899 from NIAMS/NIH.
(143) Vitamin D deficiency as a mediator of ethnic differences in experimental pain: preliminary findings T Glover, B Goodin, L Kindler, C King, K Sibille, A Horgas, C Peloquin, J Riley, R Staud, L Bradley, and R Fillingim; University of Florida, Gainesville, FL Ethnic differences in quantitative sensory testing have previously been demonstrated along with separate studies showing greater vitamin D deficiency in ethnic minorities. While preliminary reports suggest that vitamin D deficiency is implicated in several health conditions, few studies have investigated whether ethnic differences in pain might be explained by differences in vitamin D levels. The purpose of this study was to examine whether vitamin D levels mediate ethnic differences in experimental pain. Serum was collected for vitamin D analyte (25-hydroxyvitamin D (25[OH]D). The sample consisted of 64 (68% female) ethnically diverse (63% Caucasian, 36% African American) community-dwelling middle-aged and older adults with a mean age of 57 years. Controlling for sex, age, and presence of knee pain, regression analysis revealed that ethnicity was significantly related to pressure pain threshold (b=.26; p=.04) and heat pain tolerance (b=.44; p<.001) but not heat pain threshold (b=.07; p=.58) assessed at the knee. In general, African Americans demonstrated greater pain sensitivity than their Caucasian counterparts. Further, ethnicity was significantly related to vitamin D level (b=.47; p<.001) with African Americans demonstrating greater vitamin D deficiency than Caucasians. Controlling for previously mentioned covariates and ethnicity, diminished vitamin D was significantly related to lower pressure pain thresholds (b=.29; p=.04) but not heat pain tolerance (b=.19; p=.17). Using a bias-corrected bootstrapped confidence interval, results showed that diminished vitamin D significantly mediated the relationship between ethnicity and pressure pain threshold (95% BC CI: .054 to .946 with 1000 resamples) assessed at the knee. To our knowledge, these data are the first to support that ethnic differences in pain are mediated by differences in vitamin D level. Vitamin D deficiency may be a risk factor for increased pain experience in African Americans. As data collection progresses, relationships between vitamin D levels, pain, and ethnicity will be more fully explored.
(141) A pain in the neck? Which regions of body pain are most associated with pain interference and other health outcomes 6 weeks after motor vehicle collision K Whittington, A Bortsov, A Soward, J Jones, D Peak, R Swor, D Lee, N Rathlev, R Domeier, P Hendry, W Maixner, G Slade, and S McLean; University of North Carolina , Chapel Hill, NC Traditionally, studies examining persistent post-motor vehicle collision (MVC) pain have focused on the neck region (Whiplash-Associated Disorders), however several recent studies have demonstrated that persistent post-MVC pain is not limited to the neck region. We assessed which regions of body pain are most associated with pain interference and other health outcomes 6 weeks after MVC using data from a prospective, multisite, longitudinal study of patients (n = 427) enrolled in the emergency department after MVC. Among patients reporting persistent post-MVC pain in one or more body regions 6 weeks after MVC (n = 321), we examined the strength of association (assessed via unstandardized beta regression coefficient) between pain severity (0-10 numeric rating scale) in each body region (Regional Pain Scale) and MVC-related pain interference (Brief Pain Inventory subscales) and other health outcomes: post-traumatic stress disorder (PTSD) symptoms (Impact of Events Scale-Revised), depressive symptoms (Center for Epidemiological Studies Depression Scale), and mental and physical health (Short Form 12 Health Survey MCS, PCS). For each outcome, pain regions were then ranked according to strength of association, and mean rankings across pain interference subscales were calculated. Pain in the neck region had the highest mean ranking across pain interference subscales 6 weeks after MVC, followed by pain in the abdomen, upper back, head, and lower back regions. Pain in the neck region was also most strongly associated with depressive symptoms, physical health, and mental health. Pain in the abdominal region was the next most strongly associated with these three outcomes, and was the pain region most strongly associated with comorbid PTSD symptoms. These findings broadly support an emphasis on the neck region when examining post-MVC pain outcomes, while highlighting the important influence of pain in a number of body regions on pain interference and emotional and physical health outcomes. Funded by NIH 1R01AR056328.
The Journal of Pain
P11
A09 Prediction of Outcome (142) Experimental pain sensitivity does not differ three months after surgery in patients with high and low clinical pain intensity C Valencia, R Fillingim, and S George; University of Florida, Gainesville, FL The transition to a chronic pain state could be influenced by neuroplastic changes in the central nervous system (CNS) induced by surgery. Conditioned pain modulation (CPM), temporal summation (TS), and hyperalgesia have been linked to the development of chronic pain, but have not been widely studied in post-operative models. The purposes of this study were to investigate: 1) baseline differences in CPM, TS and pain threshold between patients having shoulder surgery and healthy controls, and 2) whether CPM, TS and pain threshold differentially change over time between patients with high and low clinical pain. TS was generated with repeated thermal stimuli, CPM was assessed using TS as the experimental stimulus and cold water bath as the conditioning stimulus, and threshold was assessed with thermal stimuli. Three months after surgery patients were classified by the Brief Pain Inventory (BPI) into high and low clinical pain intensity groups. There were no baseline differences on CPM, TS, and threshold among the 3 groups (2 patient groups and age, sex matched controls). Furthermore, there were no differential changes for CPM, TS or threshold between the high and low clinical pain groups. The results of the present study revealed that for this surgical model there was no evidence of: 1) enhanced CNS processing of pain at baseline, and 2) changes in CNS processing during 3 month post-operative period. These results suggest that 3 months may not be a sufficient time period to reveal neuroplastic changes in the CNS, or that development of chronic pain may occur through different pathways for this patient population. Grant #AR055899 from NIAMS/NIH.
(143) Vitamin D deficiency as a mediator of ethnic differences in experimental pain: preliminary findings T Glover, B Goodin, L Kindler, C King, K Sibille, A Horgas, C Peloquin, J Riley, R Staud, L Bradley, and R Fillingim; University of Florida, Gainesville, FL Ethnic differences in quantitative sensory testing have previously been demonstrated along with separate studies showing greater vitamin D deficiency in ethnic minorities. While preliminary reports suggest that vitamin D deficiency is implicated in several health conditions, few studies have investigated whether ethnic differences in pain might be explained by differences in vitamin D levels. The purpose of this study was to examine whether vitamin D levels mediate ethnic differences in experimental pain. Serum was collected for vitamin D analyte (25-hydroxyvitamin D (25[OH]D). The sample consisted of 64 (68% female) ethnically diverse (63% Caucasian, 36% African American) community-dwelling middle-aged and older adults with a mean age of 57 years. Controlling for sex, age, and presence of knee pain, regression analysis revealed that ethnicity was significantly related to pressure pain threshold (b=.26; p=.04) and heat pain tolerance (b=.44; p<.001) but not heat pain threshold (b=.07; p=.58) assessed at the knee. In general, African Americans demonstrated greater pain sensitivity than their Caucasian counterparts. Further, ethnicity was significantly related to vitamin D level (b=.47; p<.001) with African Americans demonstrating greater vitamin D deficiency than Caucasians. Controlling for previously mentioned covariates and ethnicity, diminished vitamin D was significantly related to lower pressure pain thresholds (b=.29; p=.04) but not heat pain tolerance (b=.19; p=.17). Using a bias-corrected bootstrapped confidence interval, results showed that diminished vitamin D significantly mediated the relationship between ethnicity and pressure pain threshold (95% BC CI: .054 to .946 with 1000 resamples) assessed at the knee. To our knowledge, these data are the first to support that ethnic differences in pain are mediated by differences in vitamin D level. Vitamin D deficiency may be a risk factor for increased pain experience in African Americans. As data collection progresses, relationships between vitamin D levels, pain, and ethnicity will be more fully explored.