The journal of pain : official journal of the American Pain Society
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Randomized Controlled Trial
Respiration-induced hypoalgesia: exploration of potential mechanisms.
Slow breathing is used as a means to reduce pain, yet the mechanisms responsible for respiration-induced hypoalgesia are poorly understood. The present study asked 30 healthy participants (M(age) = 21 years, M(education) = 15 years, 80% white non-Hispanic) to breathe at normal, slow (50% normal), and fast (125% normal) rates while constant-intensity, suprathreshold electric stimulations were delivered to the sural nerve to elicit pain and the nociceptive flexion reflex (NFR, a measure of spinal nociception). Stimulations were equally balanced across inhalations and exhalations to determine whether parasympathetic activation during exhalations contributes to hypoalgesia. Respiration rate, heart rate variability (HRV, a measure of parasympathetic activity), heart rate, and subjective arousal were assessed as manipulation checks. Slow breathing reduced pain relative to normal breathing and fast breathing, but NFR was not influenced by breathing. Further, pain and NFR did not differ between exhalations and inhalations, and changes in HRV did not correlate with changes in pain or NFR. Together, these findings suggest that respiration-induced hypoalgesia does not require gating of spinal nociception or changes in parasympathetic activity. ⋯ Slow breathing reduced pain relative to normal and fast breathing. This respiration-induced hypoalgesia does not appear to be due to gating of spinal nociception or changes in parasympathetic activity.
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In the present study, patients with musculoskeletal pain conditions (n = 55) were filmed while performing a lifting task designed to elicit pain behaviors. Patients were asked to perform the lifting task twice, under 2 distinct conditions. In the first condition, patients were asked to rate their pain while lifting a series of weights. In the second condition, patients were asked to estimate the weight of the objects they lifted. The weight estimation condition was conceived as a way to increase the cognitive load associated with the lifting task. The primary purpose of the present study was to examine whether manipulation of cognitive load differentially influenced the expression of pain behaviors in high and low catastrophizers. During the pain rating condition, results indicated that high catastrophizers displayed significantly higher levels of communicative and protective pain behaviors than low catastrophizers. During the weight estimation condition, however, high and low catastrophizers no longer differed in the expression of communicative pain behaviors. These results suggest that increasing cognitive load during a pain-eliciting task may interfere with the expression of communicative pain behaviors in high catastrophizers. The discussion addresses the potential role of automatic and cognitive control processes in the expression of pain behaviors. ⋯ The present study provides new insights into the processes that might underlie the expression of pain behaviors in patients with high levels of catastrophizing. Our findings could have implications for the management of patients presenting with pain conditions, particularly those with high levels of catastrophizing.
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We previously showed evidence for a genetic association of the human leukocyte antigen (HLA) system and complex regional pain syndrome (CRPS) with dystonia. Involvement of the HLA system suggests that CRPS has a genetic component with perturbed regulation of inflammation and neuroplasticity as possible disease mechanisms. However, it is at present unclear whether the observed association with HLA-B62 and HLA-DQ8 in CRPS patients with dystonia also holds true for patients without dystonia. Therefore, we tested the possible association with HLA-B62 and HLA-DQ8 in a clinically homogeneous group of 131 CRPS patients without dystonia. In addition, we investigated the possible association with other alleles of the HLA-A, HLA-B, HLA-C, HLA-DR, and HLA-DQ loci. We showed an increased prevalence of HLA-DQ8 (molecularly typed as HLA-DQB1*03:02; OR = 1.65 [95% CI 1.12-2.42], P = .014) in CRPS without dystonia, whereas no association was observed for HLA-B62 (molecularly typed as HLA-B*15:01; OR = 1.22 [95% CI .78-1.92], P = .458). Our data suggest that CRPS with and CRPS without dystonia may be genetically different, but overlapping, disease entities because only HLA-DQ8 is associated with both. The findings also indicate that distinct biological pathways may play a role in both CRPS subtypes. ⋯ This study is the first to replicate a specific HLA region conferring genetic risk for the development of CRPS. Moreover, associations of HLA-DQ8 with both CRPS with and CRPS without dystonia, and HLA-B62 only with CRPS with dystonia, suggest that these disease entities may be genetically different, but overlapping.
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A cross-sectional nationwide epidemiological study was performed in a random sample of the Portuguese adult population, aiming to describe the prevalence and impact of chronic pain (CP). The 5,094 participants were selected by random digit dialing, between January 2007 and March 2008, and estimates were adequately weighted for the population. Prevalence of CP was 36.7% (95% confidence interval [CI] [35.3-38.2]), based on the definition of the International Association for the Study of Pain. Recurrent or continuous pain was present in 85% of those with CP, and moderate-to-severe intensity and disability were present in 68 and 35%, respectively. Highest CP prevalence was observed among the elderly, retired, unemployed, and less educated. Highest disability was found in relation with family/home responsibilities, recreational activities, occupation/work, and sleep/rest; 13% reported a diagnosis of depression and 49% reported interference in their job. The main factors associated with disability were sex, pain intensity, and depression or depressive symptoms. CP is highly prevalent, causes high personal and social burden, and affects particularly the most vulnerable subgroups. Portugal, depending on CP definition, could be placed in the lower prevalence group in Europe. Improvement in pain intensity management and special attention to affective components of CP are recommended. ⋯ In this cross-sectional nationwide epidemiological study, we showed that chronic pain is a significant problem that is present in 37% of the Portuguese adult general population, is associated with high personal, family, and social burden, and affects in particular the most vulnerable subgroups of the population.
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In 2008, according to the Medical Expenditure Panel Survey (MEPS), about 100 million adults in the United States were affected by chronic pain, including joint pain or arthritis. Pain is costly to the nation because it requires medical treatment and complicates treatment for other ailments. Also, pain lowers worker productivity. Using the 2008 MEPS, we estimated 1) the portion of total U.S. health care costs attributable to pain; and 2) the annual costs of pain associated with lower worker productivity. We found that the total costs ranged from $560 to $635 billion in 2010 dollars. The additional health care costs due to pain ranged from $261 to $300 billion. This represents an increase in annual per person health care costs ranging from $261 to $300 compared to a base of about $4,250 for persons without pain. The value of lost productivity due to pain ranged from $299 to $335 billion. We found that the annual cost of pain was greater than the annual costs of heart disease ($309 billion), cancer ($243 billion), and diabetes ($188 billion). Our estimates are conservative because they do not include costs associated with pain for nursing home residents, children, military personnel, and persons who are incarcerated. ⋯ This study estimates that the national cost of pain ranges from $560 to $635 billion, larger than the cost of the nation's priority health conditions. Because of its economic toll on society, the nation should invest in research, education, and training to advocate the successful treatment, management, and prevention of pain.