Nicola Torrance

Neuropathic pain in the general population: A systematic review of epidemiological studies

Summary This systematic review includes epidemiological studies of neuropathic pain within the general population. There is a wide range of incidence and prevalence rates. ABSTRACT Most patients with neuropathic pain symptoms present and are managed in primary care, with only a minority being referred for specialist clinical assessment and diagnoses. Previous reviews have focused mainly on specific neuropathic pain conditions based in specialist settings. This is the first systematic review of epidemiological studies of neuropathic pain in the general population. Electronic databases were searched from January 1966 to December 2012, and studies were included where the main focus was on neuropathic pain prevalence and/or incidence, either as part of a specific neuropathic pain‐related condition or as a global entity in the general population. We excluded studies in which data were extracted from pain or other specialist clinics or focusing on specific population subgroups. Twenty‐one articles were identified and underwent quality assessment and data extraction. Included studies differed in 3 main ways: method of data retrieval, case ascertainment tool used, and presentation of prevalence/incidence rates. This heterogeneity precluded any meta‐analysis. We categorised comparable incidence and prevalence rates into 2 main subgroups: (1) chronic pain with neuropathic characteristics (range 3–17%), and (2) neuropathic pain associated with a specific condition, including postherpetic neuralgia (3.9–42.0/100,000 person–years [PY]), trigeminal neuralgia (12.6–28.9/100,000 PY), painful diabetic peripheral neuropathy (15.3–72.3/100,000 PY), glossopharyngeal neuralgia (0.2–0.4/100,000 PY). These differences highlight the importance of a standardised approach for identifying neuropathic pain in future epidemiological studies. A best estimate of population prevalence of pain with neuropathic characteristics is likely to lie between 6.9% and 10%.

Health and quality of life associated with chronic pain of predominantly neuropathic origin in the community.

ObjectivesTo assess the health and quality of life associated with chronic pain of predominantly neuropathic origin (POPNO) on health and daily activity in the general population. MethodsThe Self-complete Leeds Assessment of Neuropathic Symptoms and Signs (S-LANSS) questionnaire, recently validated for identifying pain of predominantly neuropathic origin, was sent to 6000 adults identified from general practices in the United Kingdom, along with chronic pain identification and severity questions, the Brief Pain Inventory (BPI), the Neuropathic Pain Scale, and the SF-36 general health questionnaire. ResultsWith a corrected response rate of 52%, 3 groups of respondents were identified: those without chronic pain (“No Chronic Pain” group, n=1537); those with chronic pain who were S-LANSS positive indicating the presence of POPNO (“Chronic POPNO” group, n =241); and those with chronic pain who were S-LANSS negative [“Chronic Pain (non-POPNO)” group, n=1179]. The chronic POPNO group reported higher pain severity and had significantly poorer scores for all interference items of the BPI than those with chronic pain (non-POPNO). Mean scores from the Neuropathic Pain Scale were also significantly higher for the Chronic POPNO group. There were significant differences between the groups in all domains of the SF-36, with the Chronic POPNO group reporting the worst health. After adjusting for pain severity, age, and sex, the chronic POPNO group was still found to have poorer scores than the other Chronic Pain (non-POPNO) group in all domains of the SF-36 and all interference items in the BPI, indicating poorer health and greater disability. DiscussionThis study confirms the importance of identifying neuropathic pain in the community, and the need for multidimensional management strategies that address all aspects of health.

Chronic pain epidemiology and its clinical relevance

Chronic pain affects ∼20% of the European population and is commoner in women, older people, and with relative deprivation. Its management in the community remains generally unsatisfactory, partly because of lack of evidence for effective interventions. Epidemiological study of chronic pain, through an understanding of its distribution and determinants, can inform the development, targeting, and evaluation of interventions in the general population. This paper reviews current knowledge of risk markers associated with chronic pain and considers how these might inform management and prevention. Risk factors include socio-demographic, clinical, psychological, and biological factors. These are relevant to our understanding of chronic pain mechanisms and the nature of, and responses to, current and future treatments.

Can pain can be more or less neuropathic? Comparison of symptom assessment tools with ratings of certainty by clinicians

Abstract Chronic pain is generally regarded as being divided into two mutually exclusive pain mechanisms: nociceptive and neuropathic. Recently, this dichotomous approach has been questioned and a model of chronic pain being ‘more or less neuropathic’ has been suggested. To test whether such a spectrum exists, we examined responses by patients with chronic pain to validated neuropathic pain assessment tools and compared these with ratings of certainty about the neuropathic origin of pain by their specialist pain physicians. We examined 200 patients (100 each with nociceptive and neuropathic pain) and administered the self‐complete Leeds Assessment of Neuropathic Symptoms and Signs (S‐LANSS score) and the Neuropathic Pain Scale (NPS). Clinicians were asked to rate their certainty of the presence of neuropathic pain mechanisms on a 100 mm visual analogue scale (VAS) (0 = ‘not at all neuropathic in origin’ to 100 = ‘completely neuropathic in origin’). The whole sample was divided into tertiles based on ascending ratings of diagnostic certainty by clinicians using the VAS and labelled ‘unlikely’, ‘possible’ and ‘definite’ neuropathic pain. There were significant differences in median S‐LANSS and NPS composite scores between all tertile groups. There were also significant differences between many S‐LANSS and NPS item scores between groups. We have shown that higher scores on both the S‐LANSS and the NPS are indicative of greater clinician certainty of neuropathic pain mechanisms being present. These data support the theoretical construct that pain can be more or less neuropathic and that pain of predominantly neuropathic origin may be a useful clinical concept.

Severe chronic pain is associated with increased 10 year mortality. A cohort record linkage study

Previous research has clearly demonstrated a link between chronic pain and poor health, and has suggested a link with increased mortality, though the latter is less consistent. In 1996 a cohort of 6940 individuals was recruited, and information collected, about reported chronic pain status, general health and socio‐demographic details. Ten years later, a record linkage was conducted between these data and the routinely collected national dataset for death registration. Primary cause of death was classified according to ICD‐10 codes. Survival analysis was conducted to obtain unadjusted and multi‐adjusted hazard ratios (HR) for all‐cause, system‐specific and disease‐specific mortality by chronic pain status. A total of 5858 (84.4%) of individuals from the original cohort were linked, including 1557 (26.6%) who had died. Survival analysis found significant associations between any reported chronic pain and all‐cause mortality (HR 1.32, 99% CI, 1.14–1.54) and a number of specific causes. However, when we adjusted for socio‐demographic factors and reported long‐term limiting illness, the significant association was lost. Survival among those reporting severe chronic pain was significantly worse than among those reporting mild or no chronic pain. After adjustment for socio‐demographic factors and reported long‐term limiting illness, severe chronic pain remained significantly associated with all‐cause mortality (HR 1.49, 99% CI 1.21–1.84) and all circulatory system disease deaths (HR 1.68, 99% CI 1.20–2.35). The evident association between any chronic pain and increased mortality can apparently be explained by confounding caused by socio‐demographic factors. However, severe chronic pain is associated with increased risk of mortality, independent of socio‐demographic factors.

Epidemiology of Neuropathic Pain and Its Impact on Quality of Life

Epidemiology is an important clinical tool in designing and evaluating management and prevention strategies, and is particularly relevant to neuropathic pain. However, there is a relative lack of accurate information available. In one sense, neuropathic pain describes a symptom or a mechanism, rather than a specific disease; on the other hand, there are sufficient similarities in the effects and response to treatment between different causes to make it worthwhile to consider neuropathic pain as a distinct condition. However, there are important specific disease-based factors that need to be considered separately. Estimates of prevalence that are based on specific causes of neuropathic pain tend to be lower (1–2%) than those that are based on reports of the classic symptoms (6–8%), and further methodological research is needed. All neuropathic pain is associated with poor general health, comparable with other severe chronic diseases. The importance of newly proposed risk factors, including genetic factors, still needs to be assessed at a population level.

Neuropathic pain in the community: More under-treated than refractory?

Summary There is a significant proportion of chronic pain that is persistent and neuropathic, appears undertreated or untreated, and is associated with poor health and quality of life. Abstract Best current estimates of neuropathic pain prevalence come from studies using screening tools detecting pain with probable neuropathic features; the proportion experiencing significant, long‐term neuropathic pain, and the proportion not responding to standard treatment are unknown. These “refractory” cases are the most clinically important to detect, being the most severe, requiring specialist treatment. The aim of this study was to estimate the proportion of neuropathic pain in the population that is “refractory,” and to quantify associated clinical and demographic features. We posted self‐administered questionnaires to 10,000 adult patients randomly selected from 10 general practitioner practices in 5 UK locations. The questionnaire contained chronic pain identification and severity questions, cause of pain, SF‐12, EQ‐5D, S‐LANSS (Self‐administered Leeds Assessment of Neuropathic Signs and Symptoms), PSEQ (Pain Self‐Efficacy Questionnaire), use of neuropathic pain medications, and health care utilisation. These data were combined to determine the presence and characteristics of “refractory” neuropathic pain according to the defining features identified by a Delphi survey of international experts. Graded categories of chronic pain with and without neuropathic characteristics were generated, incorporating the refractory criteria. Completed questionnaires were returned by 4451 individuals (response rate 47%); 399 had “chronic pain with neuropathic characteristics” (S‐LANSS positive, 8.9% of the study sample); 215 (53.9%) also reported a positive relevant history (“Possible neuropathic pain”); and 98 (4.5% of all Chronic Pain) also reported an “adequate” trial of at least one neuropathic pain drug (“Treated possible neuropathic pain”). The most refractory cases were associated with dramatically poorer physical and mental health, lower pain self‐efficacy, higher pain intensity and pain‐related disability, and greater health care service use.

Management of chronic pain in primary care.

Purpose of reviewTo examine recent and current evidence available to guide the management of chronic pain in primary care. Recent findingsThe growing profile of chronic pain has facilitated some important consensus and guideline statements. Pharmacological management, based on available evidence and consensus, is essential in managing chronic pain in primary care, as part of a holistic approach, and with regular review. Studies of primary care management of chronic pain face considerable challenges, with assessment and interventions that are complex, and involving multidisciplinary approaches. Recent research evidence points to the effectiveness and feasibility of multidisciplinary interventions, with appropriate assessment and training. Specifically, a self-management programme, ‘collaborative care’, a cognitive-behavioural approach, and the Alexander technique show evidence of effectiveness in primary care, the latter two also proving cost-effective. SummaryMost chronic pain presents and is managed in primary care; yet, most evidence for its management is difficult to apply in the primary care setting. Despite growing evidence for the management of chronic pain generally, management in primary care must be largely guided by consensus, experience, and judicious extrapolation from research in other contexts or conditions. A need for increased and on-going education and resources is apparent, as is the need for more research based in primary care.

Chronic pain epidemiology - where do lifestyle factors fit in?

Chronic pain is common and complex and has a large impact on individuals and society. Good epidemiological pain data provide key information on the use of resources (both in general practice and in specialist clinics), insight into factors that lead to or favour chronicity and the design of interventions aimed at reducing or preventing the effects of chronic pain. This review aims to highlight the important factors associated with chronic pain, including those factors which are amenable to lifestyle intervention.

Estimating the burden of disease in chronic pain with and without neuropathic characteristics: does the choice between the EQ-5D and SF-6D matter?

&NA; Chronic pain with neuropathic characteristics is associated with significantly lower EQ‐5D and Short Form 6D health utilities scores, with 17% reporting health states “worse than death”. &NA; The EQ‐5D and Short Form (SF)12 are widely used generic health‐related quality of life (HRQoL) questionnaires. They can be used to derive health utility index scores, on a scale where 0 is equivalent to death and 1 represents full health, with scores less than zero representing states “worse than death.” We compared EQ‐5D or SF‐6D health utility index scores in patients with no chronic pain, and chronic pain with and without neuropathic characteristics (NC), and to explore their discriminant ability for pain severity. Self‐reported health and chronic pain status was collected as part of a UK general population survey (n = 4451). We found moderate agreement between individual dimensions of EQ‐5D and SF‐6D, with most highly correlated dimensions found for mental health and anxiety/depression, role limitations and usual activities, and pain and pain/discomfort. Overall 43% reported full health on the EQ‐5D, compared with only 4.2% on the SF‐6D. There were significant differences in mean utilities for chronic pain with NC (EQ‐5D 0.47 vs SF‐6D 0.62) and especially for severe pain (EQ‐5D 0.33 vs SF‐6D 0.58). On the EQ‐5D, 17% of those with chronic pain with NC and 3% without NC scored “worse than death,” a state which is not possible using the SF‐6D. Health utilities derived from EQ‐5D and SF‐12/36 can discriminate between group differences for chronic pain with and without NC and greater pain severity. However, the instruments generate widely differing HRQoL scores for the same patient groups. The choice between using the EQ‐5D or SF‐6D matters greatly when estimating the burden of disease.