Time to reconsider what Global Burden of Disease studies really tell us about low back pain.

Most of us have read publications where the introduction includes a statistic from one of the Global Burden of Disease (GBD) studies.1 2 We may be told that musculoskeletal conditions are very common,3 low back pain (LBP) is the leading cause of disability worldwide,4 neck pain is most prevalent in Scandinavia3 and the burden of osteoarthritis is increasing,5 but have you ever stopped to think about the data underpinning these claims? In this perspective, we considered three limitations of the GBD Study that need to be borne in mind when considering GBD Study results. We used LBP as an exemplar, but the limitations apply more generally. But first we begin with an introduction to the metrics used in the GBD Study. ### GBD 101 There are four GBD Study metrics commonly used to provide information on the societal impact of LBP: incidence, prevalence, years lived with disability (YLDs) and disability adjusted life years (DALYs). Incidence reflects the number of new cases of LBP. Prevalence describes the proportion of the population experiencing LBP and is important as it drives the final two metrics. YLD estimates the amount of healthy life that is lost due to poor health, where 1 YLD represents the equivalent of 1 full year of healthy life lost. DALYs combine years of life lost (YLL) due to poor health (YLD) and YLL due to premature mortality. One DALY represents 1 year of healthy life lost because of poor health or premature mortality. The GBD Study estimates loss of healthy life with disability weights proportional to the severity of ill health. For LBP, there are six health states representing increasingly severe LBP (table 1). Severity distributions are used to describe the proportion of the population with LBP experiencing each of these six health states. View this table: Table 1 Low back pain (LBP) …