Neck pain is becoming increasingly common throughout the world. It has a considerable impact on individuals and their families, communities, health-care systems, and businesses. There is substantial heterogeneity between neck pain epidemiological studies, which makes it difficult to compare or pool data from different studies. The estimated 1 year incidence of neck pain from available studies ranges between 10.4% and 21.3% with a higher incidence noted in office and computer workers. While some studies report that between 33% and 65% of people have recovered from an episode of neck pain at 1 year, most cases run an episodic course over a person’s lifetime and, thus, relapses are common. The overall prevalence of neck pain in the general population ranges between 0.4% and 86.8% (mean: 23.1%); point prevalence ranges from 0.4% to 41.5% (mean: 14.4%); and 1 year prevalence ranges from 4.8% to 79.5% (mean: 25.8%). Prevalence is generally higher in women, higher in high-income countries compared with low- and middle-income countries and higher in urban areas compared with rural areas. Many environmental and personal factors influence the onset and course of neck pain. Most studies indicate a higher incidence of neck pain among women and an increased risk of developing neck pain until the 35–49-year age group, after which the risk begins to decline. The Global Burden of Disease 2005 Study is currently making estimates of the global burden of neck pain in relation to impairment and activity limitation, and results will be available in 2011.
Neck pain is a common condition, which causes substantial disability and economic cost . While much of the epidemiological literature on neck pain varies significantly with respect to methodology, which limits the ability to compare and pool data across studies, data consistently show that neck pain is widespread throughout many regions of the world, and appears to be increasing in both the general population and specific occupational groups .
In assessing health priorities, allocating resources and evaluating the potential costs and benefits of public health interventions, governments consider the burden of a disease and its contribution to the overall health of the population relative to other diseases . Burden of disease rankings are based on how much death and disability each disease causes. Global Burden of Disease (GBD) studies provide these rankings for the world and its major regions.
The GBD 2005 study (GBD 2005) is currently being undertaken to estimate the 2005 burden for more than 175 diseases and injuries . The methods used will also be retrospectively applied to 1990 data to revise the original GBD estimates . This is the first time the global burden of neck pain has been assessed using burden of disease methods. Epidemiological parameters, such as prevalence, incidence and remission, are important in the estimation of disease burden. In this article, we describe the process we have adopted to identify data for estimating the global burden of neck pain for GBD 2005. We briefly present a summary of our results together with an overview of the neck pain epidemiological literature.
Case definition
There is extensive variation in the way neck pain is defined in the literature . For the purposes of GBD 2005, the case definition for neck pain needed to be aligned with the epidemiological literature on neck pain to ensure we had sufficient data to support our estimates. The Bone and Joint Decade 2000–2010 Task Force on Neck Pain and its Associated Disorders (BJD–TF–NP) recently conducted a series of reviews of the epidemiological literature, and found more than 300 case definitions for neck pain . In particular, they found variation regarding the specific anatomical region under study and the recall period used. Some studies made estimates for pain in the ‘neck’, while others made estimates for pain in the ‘neck or shoulder’ region, ‘neck or upper thoracic’ region or some other variation. Some provided a diagram to specifically indicate the region that was being studied, while others did not, and some prevalence studies made estimates of ‘current’ neck pain (point prevalence), some made estimates of period prevalence (e.g., one-year, lifetime and so on), and others provided estimates of both point and period prevalence.
The Task Force proposed a framework for defining neck pain in epidemiological studies. This consists of five axes which they recommend are clearly described when reporting on the studies: (1) the source of subjects and data; (2) the setting or sampling frame; (3) the severity of neck pain and its consequences; (4) the duration of neck pain; and (5) its pattern over time . They also recommended studies use a standardised anatomical case definition for neck pain .
Using the five axes described above, we sought epidemiological data from surveys that had mainly focussed on the general population; we included any mildly, moderately or severely activity-limiting neck pain; and the minimum duration of an episode was set at 1 day to exclude trivial pain. For the purpose of GBD 2005, we used the following case definition: ‘Activity-limiting neck pain (±pain referred into the upper limb(s)) that lasts for at least 1 day.’ We used the anatomical definition as recommended by the (BJD–TF–NP) and we included cases that had pain in other areas, such as the head and trunk, provided pain was present in the neck . We assumed ‘neck or shoulder’ pain is a proxy for ‘neck’ pain.
For case definitions that differed from this, we used a Bayesian function of a program called DisMod III to convert these to our GBD case definition. This will be reported on in more detail in a later publication.
Functional health states
We developed a set of discrete health states to describe the severity levels and disabling consequences of neck pain. These were chosen and defined according to the natural history of neck pain, identification of paths within that natural history that result in a significant loss of functioning and the availability of sufficient epidemiological data on these health states to enable their use in the calculation of the burden of neck pain.
The International Classification of Functioning, Disability and Health (ICF) states that disability may constitute impairments of body functions and structures, activity limitations and/or participation restrictions . While loss of function in burden of disease terminology can be defined as any departure from an ‘ideal health state’, for the purpose GBD 2005, functional loss is limited to impairments of body structures and functions and activitylimitation. The GBD methods do not take into account burden that may result from broader constructs, such as participation, well-being, increased pressure on health-care systems or economic cost, and this needs to be considered when interpreting burden of disease study results. With regard to activity limitation, we attempted to count ‘any’ activity-limiting neck pain, irrespective of whether it was mildly, moderately or severely activity-limiting.
Similar to other diseases in GBD 2005, it was not possible for us to list every imaginable health state for neck pain due to the time and resources required for estimating burden for each of these. As such, only the most common health states causing the greatest burden were selected. Each was defined in technical and lay terms according to a specific set of domains relating to bodily impairment and activity limitation. A health state value was derived through community and health professional surveys to reflect the severity of each of the health states on a continuum between zero (equivalent to full health) and one (equivalent to death). Lay descriptions had to be concise as pre-testing found lengthy descriptions often confused survey participants. The health states for neck pain are shown in Table 1 .
| Health state | Technical definition | Lay description |
|---|---|---|
| Acute neck pain with arm pain | Activity-limiting neck pain (with pain referred into either upper limb) that lasts for at least one day and resolves either temporarily or permanently in less than three months. | This person has severe neck pain, and difficulty turning the head and lifting things. The person gets headaches and arm pain, sleeps poorly, and feels tired and worried. |
| Acute neck pain without arm pain | Activity-limiting neck pain (with no pain referred into either upper limb) that lasts for at least one day and resolves either temporarily or permanently in less than three months. | This person has neck pain, and difficulty turning the head and lifting things. |
| Chronic neck pain with arm pain | Activity-limiting neck pain (with pain referred into either upper limb) that lasts for three months or more. | This person has constant neck pain and arm pain, and difficulty turning the head, holding arms up, and lifting things. The person gets headaches, sleeps poorly, and feels tired and worried. |
| Chronic neck pain without arm pain | Activity-limiting neck pain (with no pain referred into either upper limb) that lasts for three months or more. | This person has constant neck pain and difficulty turning the head, holding arms up, and lifting things. |
Functional health states
We developed a set of discrete health states to describe the severity levels and disabling consequences of neck pain. These were chosen and defined according to the natural history of neck pain, identification of paths within that natural history that result in a significant loss of functioning and the availability of sufficient epidemiological data on these health states to enable their use in the calculation of the burden of neck pain.
The International Classification of Functioning, Disability and Health (ICF) states that disability may constitute impairments of body functions and structures, activity limitations and/or participation restrictions . While loss of function in burden of disease terminology can be defined as any departure from an ‘ideal health state’, for the purpose GBD 2005, functional loss is limited to impairments of body structures and functions and activitylimitation. The GBD methods do not take into account burden that may result from broader constructs, such as participation, well-being, increased pressure on health-care systems or economic cost, and this needs to be considered when interpreting burden of disease study results. With regard to activity limitation, we attempted to count ‘any’ activity-limiting neck pain, irrespective of whether it was mildly, moderately or severely activity-limiting.
Similar to other diseases in GBD 2005, it was not possible for us to list every imaginable health state for neck pain due to the time and resources required for estimating burden for each of these. As such, only the most common health states causing the greatest burden were selected. Each was defined in technical and lay terms according to a specific set of domains relating to bodily impairment and activity limitation. A health state value was derived through community and health professional surveys to reflect the severity of each of the health states on a continuum between zero (equivalent to full health) and one (equivalent to death). Lay descriptions had to be concise as pre-testing found lengthy descriptions often confused survey participants. The health states for neck pain are shown in Table 1 .
| Health state | Technical definition | Lay description |
|---|---|---|
| Acute neck pain with arm pain | Activity-limiting neck pain (with pain referred into either upper limb) that lasts for at least one day and resolves either temporarily or permanently in less than three months. | This person has severe neck pain, and difficulty turning the head and lifting things. The person gets headaches and arm pain, sleeps poorly, and feels tired and worried. |
| Acute neck pain without arm pain | Activity-limiting neck pain (with no pain referred into either upper limb) that lasts for at least one day and resolves either temporarily or permanently in less than three months. | This person has neck pain, and difficulty turning the head and lifting things. |
| Chronic neck pain with arm pain | Activity-limiting neck pain (with pain referred into either upper limb) that lasts for three months or more. | This person has constant neck pain and arm pain, and difficulty turning the head, holding arms up, and lifting things. The person gets headaches, sleeps poorly, and feels tired and worried. |
| Chronic neck pain without arm pain | Activity-limiting neck pain (with no pain referred into either upper limb) that lasts for three months or more. | This person has constant neck pain and difficulty turning the head, holding arms up, and lifting things. |
Descriptive epidemiology
The major indicators of disease occurrence at a population level are incidence (number of new cases of a disease in a given time period) and prevalence (number of individuals with existing disease at a given point in time) . Most people experience neck pain at some stage in their lives . Neck pain is usually first experienced in childhood or adolescence , and, like low back pain, runs an episodic course over a person’s lifetime . Therefore, estimating the incidence of neck pain is problematic, as the cumulative incidence of first-ever episodes of neck pain is already high by early adulthood , and symptoms tend to recur over time .
In addition, fewer incidence studies have been performed as these are expensive and require longitudinal studies in comparison to cheaper cross-sectional studies that can be performed to measure prevalence. There is also substantial methodological variation between neck pain incidence studies with differences in the length of the follow-up period; baseline inclusion criteria; the case definition, including the anatomical location of neck pain and the minimum duration of the episode; and whether the number of people with one or more neck pain episodes, or the number of episodes, including repeat episodes in one individual, were being counted.
As part of GBD 2005, we conducted systematic reviews to determine the incidence, remission and prevalence of neck pain throughout the world. For each of these reviews, we searched Ovid Medline, Embase, Cinahl, CAB abstracts, WHOLIS and SIGLE databases. We sought both published and unpublished population-based studies published or performed from 1980 to 2009 inclusive. There were no language, age, gender or setting restrictions. Reference lists of the full articles retrieved for further assessment were also examined to identify additional potentially relevant articles. Studies were excluded, if they were not representative of the population as a whole (e.g., judo athletes, pregnant women, miners, military, etc., or hospital- or clinic-based); provided no prevalence, incidence or remission data (e.g., a commentary piece, risk factor analysis, and so on); included only a specific subset of neck pain sufferers; had a sample size less than 150; or were reviews.
We developed a tool to assess the risk of bias of the included studies . In brief, the tool was modified from an existing checklist developed by Leboeuf-Yde and Lauritsen to assess the methodological quality of epidemiological surveys reporting on the occurrence of low back pain . The final risk of bias tool consisted of 10 items. Response options for each item were low and high risk of bias. Each study was also given an overall rating of high, moderate or low risk of bias. The tool was found to have a high level of inter-rater agreement (overall agreement 93%, Kappa statistic 0.83; agreement for individual items ranged from 83% to 100%, Kappa statistics 0.43–1.0) .
Incidence of neck pain
The following terms were used to identify studies for the systematic review of the incidence of neck pain in the general population: ‘neck pain’, ‘neck ache’, ‘neckache’ and ‘ cervical pain’ individually and combined with each of the following: ‘ incidence’, ‘cohort study’ and ‘longitudinal study’.
Five studies met our inclusion criteria . One was considered to have a moderate risk of bias , and the other four high risk of bias . All studies measured recurrences as well as first-ever episodes of neck pain, and all measured the number of people with an episode of neck pain as opposed to the number of episodes. The 1 year incidence of neck pain measured in four studies ranged from 10.4% to 21.3% ( Table 2 ).
| Citation | Country | Age range (years) | Inclusion criteria at baseline | Case definition a | Incidence (%) | Standard error (%) | Risk of bias |
|---|---|---|---|---|---|---|---|
| Ehrmann Feldman et al. | Canada | 10 to 14 | No neck pain at least once/week over previous six months | Neck pain at least once a week over previous six months | 10.4 | 1.9 | High |
| Stahl et al. | Finland | 9 to 12 | Seldom or no neck pain over previous three months | Neck pain at least once a month over previous three months | 21.3 | 3.0 | High |
| Croft et al. | United Kingdom | 18 to 75 | No neck pain | Neck pain | 17.9 | 1.3 | High |
| Côté et al. | Canada | 20 to 69 | No neck pain | Neck pain | 13.3 | 1.5 | Moderate |
Previous reviews have found that the incidence of neck pain varies between occupations. Côté et al. determined that office and computer workers had the highest incidence of neck disorders with an annual incidence of neck pain of 57% of asymptomatic office workers in the USA, 36% of Swedish municipal administrative workers and 34% of Finnish municipal employees . They also reported a high incidence of neck pain in health-care workers and transit operators .
Remission of neck pain
Disease burden for the purpose of GBD 2005 is calculated according to the following formula: Disability-Adjusted Life Years (DALYs) = Years of Life Lost (YLL) + Years of Life lived with a Disability (YLD), where YLD = incidence × duration ×disability weight. If incidence and duration are unavailable or the data are not robust, then DisMod III is used to derive these parameters . DisMod III requires at least three of the following parameters to produce estimates for incidence and/or duration: prevalence, remission, duration, incidence, relative risk mortality, case fatality and cause-specific mortality.
For the purpose of estimating burden of disease for GBD 2005, remission is defined as the rate at which people stop having the disease, for example, by means of a cure. If a chronic–episodic view is taken, remission using this definition is often zero, that is, the person continues having the disease until they die despite inter-episodic periods of lesser or no disability. However, many neck pain epidemiological studies consider remission to be the transition into an asymptomatic state, regardless of whether the person has subsequent episodes at some point in the future. This is being taken into account when interpreting neck pain remission data for use in GBD 2005.
For the systematic review of remission of neck pain, the following terms were used: ‘neck pain’ , ‘ neck ache’ , ‘ neckache ’ and ‘ cervical pain ’ individually and combined with each of the following: ‘ duration’, ‘ remission ’, ‘ cohort study ’ and ‘ longitudinal study’.
No population-based studies that met our inclusion criteria and provided relevant information on the remission of neck pain were identified. We therefore broadened our inclusion criteria to include study populations derived from clinic or health-care facilities. Using this strategy, we identified five studies; four from the Netherlands and one from Sweden . One of the studies was considered to have an overall low risk of bias , and the other four studies had a moderate risk of bias .
The studies varied with respect to the inclusion criteria at baseline, the case definition of neck pain and follow-up times, which varied from 6 weeks to 5 years. The average time between onset of pain and consultation was also unclear in most of the studies, making it difficult to accurately estimate the time to remission. We also noted that cases with continued neck pain at a particular follow-up time point (e.g., 6 months) might have had asymptomatic periods between this point and the baseline or other follow-up points. This may result in an underestimation of remission. Data from four studies indicated that remission at 1 year ranged from 33% to 65% ( Table 3 ).
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