Fiona M. Blyth

Chronic pain in Australia : a prevalence study

&NA; This study reports chronic pain prevalence in a randomly selected sample of the adult Australian population. Data were collected by Computer‐Assisted Telephone Interview (CATI) using randomly generated telephone numbers and a two‐stage stratified sample design. Chronic pain was defined as pain experienced every day for three months in the six months prior to interview. There were 17,543 completed interviews (response rate=70.8%). Chronic pain was reported by 17.1% of males and 20.0% of females. For males, prevalence peaked at 27.0% in the 65–69 year age group and for females, prevalence peaked at 31.0% in the oldest age group (80–84 years). Having chronic pain was significantly associated with older age, female gender, lower levels of completed education, and not having private health insurance; it was also strongly associated with receiving a disability benefit (adjusted OR=3.89, P<0.001) or unemployment benefit (adjusted OR=1.99, P<0.001); being unemployed for health reasons (adjusted OR=6.41, P<0.001); having poor self‐rated health (adjusted OR=7.24, P<0.001); and high levels of psychological distress (adjusted OR=3.16, P<0.001). Eleven per cent of males and 13.5% of females in the survey reported some degree of interference with daily activities caused by their pain. Prevalence of interference was highest in the 55–59 year age group in both males (17.2%) and females (19.7%). Younger respondents with chronic pain were proportionately most likely to report interference due to pain, affecting 84.3% of females and 75.9% of males aged 20–24 years with chronic pain. Within the subgroup of respondents reporting chronic pain, the presence of interference with daily activities caused by pain was significantly associated with younger age; female gender; and not having private health insurance. There were strong associations between having interfering chronic pain and receiving disability benefits (adjusted OR=3.31, P<0.001) or being unemployed due to health reasons (adjusted OR=7.94, P<0.001, respectively). The results show that chronic pain impacts upon a large proportion of the adult Australian population, including the working age population, and is strongly associated with markers of social disadvantage.

A systematic review of the global prevalence of low back pain

OBJECTIVE To perform a systematic review of the global prevalence of low back pain, and to examine the influence that case definition, prevalence period, and other variables have on prevalence. METHODS We conducted a new systematic review of the global prevalence of low back pain that included general population studies published between 1980 and 2009. A total of 165 studies from 54 countries were identified. Of these, 64% had been published since the last comparable review. RESULTS Low back pain was shown to be a major problem throughout the world, with the highest prevalence among female individuals and those aged 40-80 years. After adjusting for methodologic variation, the mean ± SEM point prevalence was estimated to be 11.9 ± 2.0%, and the 1-month prevalence was estimated to be 23.2 ± 2.9%. CONCLUSION As the population ages, the global number of individuals with low back pain is likely to increase substantially over the coming decades. Investigators are encouraged to adopt recent recommendations for a standard definition of low back pain and to consult a recently developed tool for assessing the risk of bias of prevalence studies.

The Epidemiology of low back pain.

Low back pain is an extremely common problem that most people experience at some point in their life. While substantial heterogeneity exists among low back pain epidemiological studies limiting the ability to compare and pool data, estimates of the 1 year incidence of a first-ever episode of low back pain range between 6.3% and 15.4%, while estimates of the 1 year incidence of any episode of low back pain range between 1.5% and 36%. In health facility- or clinic-based studies, episode remission at 1 year ranges from 54% to 90%; however, most studies do not indicate whether the episode was continuous between the baseline and follow-up time point(s). Most people who experience activity-limiting low back pain go on to have recurrent episodes. Estimates of recurrence at 1 year range from 24% to 80%. Given the variation in definitions of remission and recurrence, further population-based research is needed to assess the daily patterns of low back pain episodes over 1 year and longer. There is substantial information on low back pain prevalence and estimates of the point prevalence range from 1.0% to 58.1% (mean: 18.1%; median: 15.0%), and 1 year prevalence from 0.8% to 82.5% (mean: 38.1%; median: 37.4%). Due to the heterogeneity of the data, mean estimates need to be interpreted with caution. Many environmental and personal factors influence the onset and course of low back pain. Studies have found the incidence of low back pain is highest in the third decade, and overall prevalence increases with age until the 60-65 year age group and then gradually declines. Other commonly reported risk factors include low educational status, stress, anxiety, depression, job dissatisfaction, low levels of social support in the workplace and whole-body vibration. Low back pain has an enormous impact on individuals, families, communities, governments and businesses throughout the world. The Global Burden of Disease 2005 Study (GBD 2005) is currently making estimates of the global burden of low back pain in relation to impairment and activity limitation. Results will be available in 2011. Further research is needed to help us understand more about the broader outcomes and impacts from low back pain.

The global burden of low back pain: estimates from the Global Burden of Disease 2010 study

Objective To estimate the global burden of low back pain (LBP). Methods LBP was defined as pain in the area on the posterior aspect of the body from the lower margin of the twelfth ribs to the lower glutaeal folds with or without pain referred into one or both lower limbs that lasts for at least one day. Systematic reviews were performed of the prevalence, incidence, remission, duration, and mortality risk of LBP. Four levels of severity were identified for LBP with and without leg pain, each with their own disability weights. The disability weights were applied to prevalence values to derive the overall disability of LBP expressed as years lived with disability (YLDs). As there is no mortality from LBP, YLDs are the same as disability-adjusted life years (DALYs). Results Out of all 291 conditions studied in the Global Burden of Disease 2010 Study, LBP ranked highest in terms of disability (YLDs), and sixth in terms of overall burden (DALYs). The global point prevalence of LBP was 9.4% (95% CI 9.0 to 9.8). DALYs increased from 58.2 million (M) (95% CI 39.9M to 78.1M) in 1990 to 83.0M (95% CI 56.6M to 111.9M) in 2010. Prevalence and burden increased with age. Conclusions LBP causes more global disability than any other condition. With the ageing population, there is an urgent need for further research to better understand LBP across different settings.

Polypharmacy cutoff and outcomes: five or more medicines were used to identify community-dwelling older men at risk of different adverse outcomes

OBJECTIVE This study aimed to determine an optimal discriminating number of concomitant medications associated with geriatric syndromes, functional outcomes, and mortality in community-dwelling older men. STUDY DESIGN AND SETTING Older men aged ≥ 70 years (n=1,705), enrolled in the Concord Health and Aging in Men Project were studied. Receiver operating characteristic curve analysis using the Youden Index and the area under the curve was performed to determine discriminating number of medications in relation to each outcome. RESULTS The highest value of the Youden Index for frailty was obtained for a cutoff point of 6.5 medications compared with a cutoff of 5.5 for disability and 3.5 for cognitive impairment. For mortality and incident falls, the highest value of Youden Index was obtained for a cutoff of 4.5 medications. For every one increase in number of medications, the adjusted odds ratios were 1.13 (95% confidence interval [CI]=1.06-1.21) for frailty, 1.08 (95% CI=1.00-1.15) for disability, 1.09 (95% CI=1.04-1.15) for mortality, and 1.07 (95% CI=1.03-1.12) for incident falls. There was no association between increasing number of medications and cognitive impairment. CONCLUSION The study supports the use of five or more medications in the current definition of polypharmacy to estimate the medication-related adverse effects for frailty, disability, mortality, and falls.

Assessing risk of bias in prevalence studies: modification of an existing tool and evidence of interrater agreement

OBJECTIVE In the course of performing systematic reviews on the prevalence of low back and neck pain, we required a tool to assess the risk of study bias. Our objectives were to (1) modify an existing checklist and (2) test the final tool for interrater agreement. STUDY DESIGN AND SETTING The final tool consists of 10 items addressing four domains of bias plus a summary risk of bias assessment. Two researchers tested the interrater agreement of the tool by independently assessing 54 randomly selected studies. Interrater agreement overall and for each individual item was assessed using the proportion of agreement and Kappa statistic. RESULTS Raters found the tool easy to use, and there was high interrater agreement: overall agreement was 91% and the Kappa statistic was 0.82 (95% confidence interval: 0.76, 0.86). Agreement was almost perfect for the individual items on the tool and moderate for the summary assessment. CONCLUSION We have addressed a research gap by modifying and testing a tool to assess risk of study bias. Further research may be useful for assessing the applicability of the tool across different conditions.

Chronic pain and frequent use of health care.

&NA; Little is known about the relationship between chronic pain status and overall use of healthcare. We examined whether disabling chronic pain was associated with more frequent use of healthcare in three settings: primary care, emergency departments, and hospital admissions. We used data from Computer‐Assisted Telephone Interviews (CATI) of 17,543 residents in New South Wales, Australia aged 16 and over who were randomly sampled using a population‐based two‐stage stratified sample and random digit dialling methods. The overall response rate was 70.8%. Compared to chronic pain respondents with no or limited pain‐related disability, those with most pain‐related disability reported more: primary care visits in the last 2 weeks and last 12 months (adjusted mean number of visits 0.59 vs 0.40 and 10.72 vs 4.81, both P<0.005); hospital admissions (0.46 vs 0.18, P<0.005); and emergency department visits (0.85 vs 0.17, P>0.005). In modelling, having chronic pain per se, or having chronic pain with any level of activity interference predicted health care use after adjusting for age, gender, self‐rated health, psychological distress, comorbidity and access to care. Higher levels of pain‐related disability predicted health care use more than other pain status variables. There was a strong association between pain‐related disability and greater use of services. Further work is needed to understand the nature of this association. Given the fluctuating course of chronic pain over time, there is a significant segment of the population that may be at risk of developing higher levels of disability associated with increased use of services.

Measuring the global burden of low back pain

Low back pain is a major cause of morbidity in high-, middle- and low-income countries, yet to date it has been relatively under-prioritised and under-funded. One important reason may be the low ranking it has received relative to many other conditions included in the previous Global Burden of Disease studies, due in part to a lack of uniformity in how low back pain is defined and a paucity of suitable data. We present an overview of methods we have undertaken to ensure a more accurate estimate for low back pain in the Global Burden of Disease 2005 study. This will help clinicians to contextualise the new estimates and rankings when they become available at the end of 2010. It will also be helpful in planning further population-based epidemiological studies of low back pain to ensure their estimates can be included in the future Global Burden of Disease studies.

What do the numbers mean? Normative data in chronic pain measures

&NA; Although self‐reported measures play a central role in the assessment of pain and its treatment, it has long been recognized that interpretation of these measures is severely limited by the absence of normative data. Despite that, relatively few of the measures used in pain clinics or research studies have normative data for reference. Using a pain centre sample (n = 6124), this paper describes the development of a normative dataset on a number of commonly used pain‐related measures. The measures cover many of the key dimensions in pain assessment, including pain severity/quality, disability (physical functioning), and mood (emotional functioning). Measures of different cognitive and coping constructs are also included. Mean scores are reported for each measure according to age group, gender, pain site, as well as percentiles for different scores for patients with chronic low back pain. The potential uses for datasets of this type include the assessment and evaluation of individual cases, as well as the interpretation of published clinical trials. It is also argued that future systematic reviews of pain treatments should include consideration of such patient characteristics as pain levels, disability and mood in the studies reviewed rather than pain site and chronicity alone.

The global burden of neck pain

Objective To estimate the global burden of neck pain. Methods Neck pain was defined as pain in the neck with or without pain referred into one or both upper limbs that lasts for at least 1 day. Systematic reviews were performed of the prevalence, incidence, remission, duration and mortality risk of neck pain. Four levels of severity were identified for neck pain with and without arm pain, each with their own disability weights. A Bayesian meta-regression method was used to pool prevalence and derive missing age/sex/region/year values. The disability weights were applied to prevalence values to derive the overall disability of neck pain expressed as years lived with disability (YLDs). YLDs have the same value as disability-adjusted life years as there is no evidence of mortality associated with neck pain. Results The global point prevalence of neck pain was 4.9% (95% CI 4.6 to 5.3). Disability-adjusted life years increased from 23.9 million (95% CI 16.5 to 33.1) in 1990 to 33.6 million (95% CI 23.5 to 46.5) in 2010. Out of all 291 conditions studied in the Global Burden of Disease 2010 Study, neck pain ranked 4th highest in terms of disability as measured by YLDs, and 21st in terms of overall burden. Conclusions Neck pain is a common condition that causes substantial disability. With aging global populations, further research is urgently needed to better understand the predictors and clinical course of neck pain, as well as the ways in which neck pain can be prevented and better managed.