The global epidemiology of low back pain

Background Low back pain has been reported to be one of the most common health problems, as well as one of the most frequent activity-limiting complaints and the second leading cause of sick leave. Synthesizing information on the epidemiology of a condition such as low back pain can provide valuable information for health planning. The most recent systematic review on the prevalence of low back pain was undertaken over a decade ago and is consequently out of date. Existing tools for assessing study quality in systematic reviews of prevalence studies are considered to be of poor quality. Burden of Disease studies provide further information on how much death and disability diseases cause. Previous methods for estimating the global burden of low back pain had a number of methodological limitations, resulting in a significant underestimation of the burden of back pain. The Global Burden of Disease 2005 Study (GBD 2005) provided an opportunity to address a number of these limitations. Therefore, this thesis was undertaken to respond to two research needs: firstly, to synthesise information on the epidemiology of low back pain throughout the world; and secondly, to prepare this information for revising the global burden of low back pain as part of GBD 2005. Methods A case definition and sequelae for low back pain were first established. A tool was developed and tested for assessing risk of bias in prevalence studies, which consisted of ten individual items and a summary risk of bias assessment. A series of systematic reviews on the epidemiology of low back pain was then undertaken using best practice methods. The resulting information was synthesized in preparation for estimating the global burden of low back pain. A disease modelling program (DisMod III) was used to manage the main aspects of heterogeneity, derive missing values, ensure internal consistency, and produce a full set of age/sex/region/year-specific estimates for each disease parameter. Results The systematic reviews yielded many studies. For the prevalence review alone, 165 studies from 54 countries were identified. Of these, 64% had been published since the last review. Despite an increase in data since earlier reviews, there continues to be a paucity of information on low back pain in low- and middle-income economies. Low back pain was confirmed as an extremely common problem that most people experience at some point in their life. Most people who experience activity-limiting low back pain go on to have recurrent episodes. After analysis in DisMod III, mean global point prevalence for 2005 was estimated to be 6.2% (95% CI: 5.5 to 6.9). It was higher for acute episodes (5.3%; 95% CI: 5.1 to 5.4) compared with chronic episodes (0.9%; 95% CI: 0.8 to 1.0). Prevalence was highest in women, the 55-64 year age group and in high-income regions compared to low- and middle-income regions. It had increased from 1990 (mean: 5.7%; 95% CI: 5.1 to 6.4) to 2005 (mean: 6.2%; 95% CI: 5.5 to 6.9). In people aged 15 years and above, point prevalence in 2005 was 8.1% (95% CI: 7.2 to 9.1). The global incidence (population rate) of low back pain in 2005 was estimated to be 990 episodes/1,000 people/year (95% CI: 890 to 1,120) for acute episodes and 0.45 episodes/1,000 people/year (95% CI: 0.30 to 0.70) for chronic episodes. This equates to approximately 6.4 billion new episodes of low back pain throughout the world in 2005. Eighty-six per cent (95% CI: 84.9 to 86.7) of people remit by three months after the onset of an episode of activity-limiting low back pain, and for these people, the average time to remit was 21.9 days (95% CI: 21.1 to 22.8). After adjustment in DisMod III, the average duration of low back pain in 2005 was estimated to be 22.6 days (95% CI: 20.3 to 24.8) for acute episodes and 25.3 years (95% CI: 18.3 to 30.5) for chronic episodes. The proportion of time that a person with an episode of low back pain is symptomatic was estimated to be 83.4% (95% CI: 70.7 to 91.3). Implications A number of limitations from previous methods have been addressed in preparing data to estimate the global burden of low back pain. Final burden estimates will be available in 2012, and preliminary analyses suggest the global burden of low back pain will be substantially higher than previously indicated. With aging populations throughout the world, the global burden of low back pain is likely to increase over the coming decades, and further research is urgently needed to develop and evaluate approaches to mitigating this. Researchers are urged to adopt recent recommendations on defining low back pain in epidemiological studies. Importantly, opportunities for collaboration should be encouraged, and research should be owned and driven by local communities, well aligned to existing programs, and build capacity within health systems.