Prevalence of chronic pain with neuropathic characteristics in the general population

We conducted a large nationwide postal survey to estimate the prevalence of chronic pain with or without neuropathic characteristics in the French general population. A questionnaire aimed at identifying chronic pain (defined as daily pain for at least 3 months), evaluating its intensity, duration and body locations, was sent to a representative sample of 30,155 subjects. The DN4 questionnaire was used to identify neuropathic characteristics. Of the questionnaires, 24,497 (81.2%) were returned and 23,712 (96.8%) could be assessed. Seven thousand five hundred and twenty-two respondents reported chronic pain (prevalence=31.7%; [95%CI: 31.1-32.3]) and 4709 said the pain intensity was moderate to severe (prevalence=19.9%; [95%CI: 19.5-20.4]). Neuropathic characteristics were reported by 1631 respondents with chronic pain (prevalence=6.9%; [95%CI: 6.6-7.2]), which was moderate to severe in 1209 (prevalence=5.1% [95%CI: 4.8-5.4]). A higher prevalence of chronic pain with neuropathic characteristics was associated with middle age (50-64 years), manual professions and those living in rural areas. It was more frequently located in the lower limbs and its intensity and duration were higher in comparison with chronic pain without neuropathic characteristics. This large national population-based study indicates that a significant proportion of chronic pain patients report neuropathic characteristics. We identified distinctive socio-demographic profile and clinical features indicating that chronic pain with neuropathic characteristics is a specific health problem.     

A longitudinal study of the prevalence and characteristics of pain in the first 5 years following spinal cord injury

A longitudinal cohort study of 100 people with traumatic spinal cord injury (SCI) was performed to determine the prevalence and severity of different types of pain (musculoskeletal, visceral, neuropathic at-level, neuropathic below-level) at 5 years following SCI. Prospective data on the characteristics of pain up to 6 months following injury had been collected previously and allowed comparisons between the presence of pain at different time points. In addition, we sought to determine the relationship between the presence of pain and physical factors related to the injury such as level of lesion, completeness and clinical SCI syndrome. We also obtained information regarding mood, global self-rated health and the impact of pain on function. Of the 100 subjects in the original cohort, 73 were available for follow up. When all types of pain were included, 59 of the 73 subjects (81%) reported the presence of pain. Musculoskeletal pain was the most common type of pain experienced and was present in 43 subjects (59%), at-level neuropathic pain was present in 30 subjects (41%), below-level neuropathic pain was present in 25 subjects (34%) and visceral pain was present in four subjects (5%). Overall, 58% reported their pain as severe or excruciating and those with visceral pain were most likely to rate their pain in these categories. There was no relationship between the presence of pain overall and level or completeness of lesion, or type of injury. However, tetraplegics were more likely to report below-level neuropathic pain. This study prospectively demonstrates the differing time courses of different types of pain over the first 5 years following SCI. There was a strong correlation between the presence of both types of neuropathic pain at 5 years and earlier time points but both visceral pain and musculoskeletal pain demonstrated a poor correlation between time points. Chronic visceral pain occurs in a small percentage of patients and does not correlate with the presence of visceral pain early following injury. Those with neuropathic pain early following their injury are likely to continue to experience ongoing pain and the pain is likely to be severe. In contrast, chronic musculoskeletal pain is more common but less likely to be severe and cannot be predicted by the presence of pain in the first 6 months following injury.     

Comorbidity of obesity and pain in a general population: results from the Southern Pain Prevalence Study.

This cross-sectional study examines the relation between obesity and self-reported pain (moderate or severe pain occurring at least monthly) in a general population sample of adults in the southeastern United States (N = 3637). Results of the study suggest that obese adults (body mass index [BMI] >30) are more likely to experience pain than their normal-weight and underweight counterparts. Respondents classified as class I obese (BMI of 30 to 34.9) were 1.762 times as likely as the underweight and normal weight participants to report severe pain. Class II obese respondents (BMI of 35 to 39.9) were 1.888 times as likely to experience severe pain. Those respondents categorized as class III obese were most likely to report severe pain--2.297 times as likely as the underweight and normal-weight respondents. Analyses demonstrated a similar trend for respondents reporting moderate to severe pain. Adults who are obese are also more likely to report experiencing pain in multiple locations. This study complements clinical research that links pain and obesity and extends it into a general population. Because this is a cross-sectional study, further research is needed to discern causal explanations for the relation between self-reported pain and obesity. PERSPECTIVE: This article provides a population-level depiction of the positive relation between obesity and self-reported pain, which complements clinical research on the topic. It may prompt future research to shape interventions and treatment for both pain and obesity.     

The epidemiology of chronic pain of predominantly neuropathic origin. Results from a general population survey.

Progress in the understanding of chronic pain with neuropathic features has been hindered by a lack of epidemiologic research in the general population. The Leeds Assessment of Neuropathic Symptoms and Signs score (S-LANSS) was recently validated for use in postal surveys, making the identification of pain of predominantly neuropathic origin possible. Six family practices in 3 UK cities (Aberdeen, Leeds, and London) generated a total random sample of 6,000 adults. The mailed questionnaire included demographic items, chronic pain identification, and intensity questions, the S-LANSS, the Level of Expressed Needs questionnaire, and the Neuropathic Pain Scale. With a corrected response rate of 52%, the prevalence of any chronic pain was 48% and the prevalence of pain of predominantly neuropathic origin was 8%. Respondents with this chronic neuropathic pain were significantly more likely to be female, slightly older, no longer married, living in council rented accommodation, unable to work, have no educational qualifications, and be smokers than all other respondents. Multiple logistic regression modeling found that pain of predominantly neuropathic origin was independently associated with older age, gender, employment (being unable to work), and lower educational attainment. Respondents with this pain type also reported significantly greater pain intensity, higher scores on the NPS, higher levels of expressed need, and longer duration of pain. This is the first estimate of the prevalence and distribution of pain of predominantly neuropathic origin in the general population, using a previously validated and reliable data collection instrument. PERSPECTIVE: Chronic pain with neuropathic features appears to be more common in the general population than previously suggested. This type of pain is more severe than other chronic pain but distributed similarly throughout sociodemographic groups.     

Pain report and the relationship of pain to physical factors in the first 6 months following spinal cord injury.

A prospective, longitudinal study of 100 people with traumatic spinal cord injury (SCI) was performed to determine the time of onset. prevalence and severity of different types of pain (musculoskeletal, visceral, neuropathic at level, neuropathic below level) at 2, 4, 8, 13 and 26 weeks following SCI. In addition, we sought to determine the relationship between physical factors such as level of lesion, completeness and clinical SCI syndrome and the presence of pain. At 6 months following SCI, 40% of people had musculoskeletal pain, none had visceral pain, 36% had neuropathic at level pain and 19% had neuropathic below level pain. When all types of pain were included, at 6 months following injury, 64% of people in the study had pain, and 21% of people had pain that was rated as severe. Those with neuropathic below level pain were most likely to report their pain as severe or excruciating. There was no relationship between the presence of pain overall and level or completeness of lesion, or type of injury. Significant differences were found, however, when specific types of pain were examined. Musculoskeletal pain was more common in people with thoracic level injuries. Neuropathic pain associated with allodynia was more common in people who had incomplete spinal cord lesions, cervical rather than thoracic spinal cord lesions, and central cord syndrome. Therefore, this study suggests that most people continue to experience pain 6 months following spinal cord injury and 21% of people continue to experience severe pain. While the presence or absence of pain overall does not appear to be related to physical factors following SCI, there does appear to be a relationship between physical factors and pain when the pain is classified into specific types.     

Risk factors predictive of chronic postsurgical neuropathic pain: the value of the iliac crest bone harvest model

Nerve lesions and secondary hyperalgesia may both be present after surgery, and their relative contributions to chronic postsurgical neuropathic pain (CPSNP) remain unclear. This prospective study explored the roles of these factors in the development of CPSNP after iliac crest bone harvest. CPSNP was defined as pain in the area of hypoesthesia, with a positive Douleur neuropathique 4 questionnaire (DN4) score 3 months after iliac crest bone harvest. The location, intensity, and neuropathic characteristics of pain were evaluated in 82 patients who were followed for 6 months. Neuropathic characteristics were assessed by clinical examination and DN4 questionnaire. The area of secondary hyperalgesia was evaluated 48 h and 1 month after surgery. The area of mechanical hypoesthesia, detection, and mechanical pain threshold were evaluated at 48 h and at 1 and 3 months. Nineteen patients (23%) had CPSNP at 3 months. The patients who developed CPSNP had a larger area of secondary hyperalgesia at 48 h (88 cm(2) vs 33 cm(2); P=.001), higher pain intensity (numerical rating scale 6.7 vs 4.7; P=.02), and higher neuropathic characteristics score on the DN4 questionnaire (4.3 vs 2.3; P=.001). However, neither the area nor the severity of hypoesthesia differed significantly between patients with and without CPSNP. Two independent, additive predictors of CPSNP were identified: area of secondary hyperalgesia (odds ratio 1.02; P=.004) and DN4 score (odds ratio 1.94; P=.001). These findings suggest that both nerve lesions and central sensitization are involved in CPSNP development and could be seen as early warning signs.     

Modelling the prevalence and cost of back pain with neuropathic components in the general population

Background: Although there is increasing knowledge of the prevalence of neuropathic pain, little has been done to isolate the cost of neuropathic pain, especially with reference to the frequent complaint of back pain. Aims: To estimate the prevalence of neuropathic components in back pain and associated costs. Methods: We used available epidemiological data to model the prevalence of neuropathic back pain in the general adult population, combining three studies: painDETECT 1, painDETECT 2, and the German back pain research network (GBPRN) study, representing a total of 21,047 subjects. The painDETECT screening questionnaire was used in the former two surveys to assess neuropathic pain components. Costing data were obtained from 1718 participants in the GBPRN survey. Results: According to our model, approximately 4% of the general adult population experienced back pain with a neuropathic component. Owing to the greater severity of neuropathic pain, its costs were found to be disproportionately high: among patients with persistent back pain, typical costs associated with a person suffering neuropathic back pain were higher than those of an average back pain patient, and as much as 67% higher than those of a patient with nociceptive back pain only. Approximately, 16% of the total costs associated with back pain were attributable to pain with a neuropathic component. Conclusions: Back pain with neuropathic components is likely to affect a relevant proportion of the general adult population and cause a disproportionately high share of back pain‐related costs.     

A prognostic approach to defining chronic pain

This paper develops a prognostic approach to defining chronic back pain. Possible and probable chronic back pain were defined, respectively, by a 50% and an 80% (or greater) probability of future clinically significant back pain. We assessed whether an empirically derived chronic pain classification satisfied these validating criteria among 1213 primary care back pain patients assessed at baseline and at 1, 2 and 5 year follow-ups. From multiple measures of back pain intensity and dysfunction, Latent Transition Regression Analysis empirically identified four pain severity latent classes: no pain; mild pain; moderate pain and limitation; and severe, limiting pain. From one observation point to the next, patients were most likely to remain in the same pain severity class, but chronic pain was better characterized as a dynamic state than a static trait. Among persons with severe, limiting pain, prognostic variables (depression, diffuse pain, pain persistence) improved prediction of future severe, limiting pain. A risk score developed from pain severity and prognostic measures identified risk levels corresponding to 50 and 80% probability thresholds for predicting future clinically significant back pain. At baseline and 1 year, 6.1 and 4.4% of study patients met or exceeded the 80% risk threshold for probable chronic back pain. An additional 20.3% at baseline and 12.5% at 1 year met or exceeded the 50% risk threshold for possible chronic back pain. Defining chronic pain prospectively, by risk thresholds for future clinically significant pain, provides an empirically grounded approach to chronic pain assessment.