Predicting persistent neck pain: a 1-year follow-up of a population cohort
Neck pain is a common experience. Within the U.K. general population, around one fifth of adults report the onset of a new episode of neck pain during the previous year; and among European and North American populations, two thirds experience neck pain at some point during their lives. However, although the prevalence is high, it may just reflect recurrent or persistent symptoms, similar to the intermittent pain pattern described for chronic low back pain. Although a number of cross-sectional surveys have been published, there has been little research into persistent neck pain within the general population using longitudinal methods.
Identifying factors that predispose individuals to persistent neck problems may contribute to primary or secondary prevention. Primary prevention is directed toward reducing the risk of initial onset of neck pain, for example, by preventing neck injury. For clinicians treating neck pain, secondary prevention of persistence or of the recurrence of symptoms is a more pragmatic approach and involves addressing those factors that increase the risk for neck pain persisting. It is with this latter issue that the current paper and analysis is concerned.
A number of studies have examined the clinical predictors for chronicity among those who consult health services for neck pain. These include factors such as duration of current episode, disability, expectations of treatment, number of pain sites, and general well-being. In addition, prospective occupational cohort studies have identified workplace risk factors for neck pain, which include physical and psychosocial elements along with job demands and coworker support. New clinical strategies are using this information to develop interventions that aim to prevent acute neck pain from persisting. These interventions recognize that many chronic regional pain syndromes have similar risk factors, including psychosocial factors, general health, and previous pain experience; consequently, such approaches frequently use cognitive behavioral approaches.
However, published literature specifically lacks information regarding the extent of persistent neck pain in the general adult population and the factors that influence chronicity among these individuals. Thus, they focused on a longitudinal study of the general adult population and the aim was twofold: 1) to investigate the prevalence of persistent neck pain at 1-year follow-up; and 2) to explore associations for the first time, between persistence and socio-demographic, health-related, occupational, physical, and lifestyle factors within the community.
This study has been the first to investigate the prevalence of persistent neck pain and the risk factors for persistence by prospectively following a general population neck pain cohort for 1 year. They have found that after 1 year, around half (48%) of their neck pain cohort had persistent pain. This estimate is consistent with results from a 1-year follow-up study of musculoskeletal pain in preadolescents, which reported half with persistent symptoms and also with a shoulder pain population cohort, which reported 54% persistence of pain over 3 years.
They did not aim to establish the nature or pattern of symptoms experienced between baseline and follow-up surveys. However, they defined persistence as neck pain at a point in time 12 months later, recalled as having been present during the previous month and having lasted for a day or longer as indicated on a blank body mannequin, in a cohort of individuals with neck pain at baseline. Consequently, their definition will have included individuals with both recurrent and continuous experiences of neck pain.
Cross-sectional methods of obtaining study cohorts have the disadvantage of being weighted towards chronic cases, so the cohort they followed were already a more persistent pain cohort than a new neck pain cohort. However, half of their baseline cohort had neck pain that resolved by 12 months suggesting that this population was not exclusively chronic. This limitation of selection, together with their attrition rate of 58% may have restricted generalizability, but their investigation of possible response bias using the wave response variable demonstrated that there was little difference in estimates for persistence across mailings. Exposure information was obtained at baseline, and so, any recall bias at baseline could not act as a confounder for associations with persistent neck pain at follow-up. Their initial population sample had a 31% 1-month period prevalence of neck pain. This figure is similar to prevalence estimates from Norwegian and Swedish population studies and consistent with a recent U.K. study, which reported 1-week and 1-year period prevalence as 20% and 34%, respectively.
They investigated factors that predispose individuals in the general population with neck pain to persistent symptoms. The strongest predictor for persistence was age, this being most frequent in those 45 to 59 years of age (62%). This is consistent with consultation rates for dorsopathies presenting to general practice and also compares similarly with low back pain prevalence data. It appears that while gender but not age predicts neck pain onset, it is age rather than gender that predicts persistence. In the primary care setting, age (greater than 40 years) has been reported to be a strong predictor of poor prognosis. One explanation for this finding may be that there could be a higher prevalence of structural cervical spine disease (osteoarthritis or disc degeneration) in this age group, although Bogduk argues that a diagnostic label of osteoarthritis is not a common cause for neck pain.
The increased risk for persistent neck pain in individuals with comorbid low back pain supports previous research. Distinguishing between individuals who suffer isolated chronic neck pain and those who have concurrent chronic regional pain syndromes may also be clinically important. This link between comorbidity and neck pain persistence may be explained by an underlying predisposition to regional musculoskeletal pain syndromes. One such predisposition might be poor psychological health. Their findings suggest that chronic neck pain represents a distinct group among musculoskeletal syndromes and gives some support to the view that psychosocial factors are less important in neck pain than some other regional pain syndromes. The link with low back pain independently of psychosocial status would be consistent with a shared spinal pathology, common mechanical risk factors, or some aspect of central pain processing not measured by their study.
A link between previous neck trauma and neck pain has been reported, and the findings of this study lend further support to this hypothesis. This association was not confounded by time, as there was no difference in time since injury between those with persistent and nonpersistent neck pain. The mechanism for this association has yet to be established.
Among the occupational, physical activity, and lifestyle factors, not working was significantly linked to persistent neck pain, although this probably reflects a healthy worker bias: individuals with persistent pain are more likely to stop working. Interestingly, none of the specific occupational factors looking at exposure to physical demands such as standing, sitting, digging, driving, and lifting were predictive of persistent neck pain. Such factors have been shown to be prognostic for chronicity among occupational cohort studies. Capturing work-related factors that may be associated with chronic pain in the general population setting is clearly a more challenging task.
There is evidence of an association between physical activity and persistent neck pain among the general population. However, neck exercises have been shown to be helpful and are encouraged and frequently used as clinical therapy for neck pain. In their study, physical activity was not a significant independent risk factor in the multivariate analysis, perhaps because of the inclusion of cycling in the same model. Cycling was observed to be a strong independent risk factor for persistent pain, and this may be an underestimate as cyclists with severe neck pain may have been discouraged from continuing this activity. They can conjecture that the cause may be linked to the impact of the postures adopted, vibrations, the neck rotation required, and the active use of neck extensor muscle groups.
To be able to directly relate their findings to clinical secondary prevention strategies, the study would have needed to be more specific to those individuals in their cohort who consulted health care services for their neck problem, and further studies are needed to take this research into the clinical arena. Another weakness was that their study lacked a measure of neck pain severity as a potential risk factor for persistence. Pain severity has been associated with chronicity in clinical studies. However, their study is important for a number of reasons. First, in terms of knowledge, it increases their understanding of the epidemiologic associations for persistent neck pain among population cohorts. Second, in terms of application, these findings help identify those at greater risk of recurrent symptoms and who may benefit most from secondary prevention methods. For example, efficient clinical secondary prevention may revolve around prioritizing patients and targeting effective strategies (e.g., health education or subsidized exercise facilities) for health care that invariably has limited resources. Occupational health strategies may encourage individuals to remain at work while pursuing pain management approaches that address issues of psychological distress. Another interesting question for future studies is whether treating low back pain among neck pain patients will reduce their risk of recurrent symptoms. With any clinical application, however, it is important to stress that their sample was a different population from those who consult health care for neck pain.
It can be seen that roughly half of those with neck pain in the community have persistent symptoms a year later. The factors that particularly predispose individuals in this study to persistence include age, being off work, low back pain, and cycling. The message for secondary prevention is perhaps to focus more on treating those at elevated risk of persistent pain i.e., those 45 to 59 years of age with neck pain, comorbid musculoskeletal pain, and those who regularly cycle. Occupational and psychological factors are reported risk factors for neck pain persistence in the workplace, but their evidence suggests that they were less influential predictors for persistent neck pain in the general population.
Finally, using the data from a published study of neck pain onset, conducted on the same sample population, a comparison of the risk factors for neck pain onset and persistence can be made. The risk factors for onset include female gender, number of children, psychological distress, previous low back pain, and previous neck injury, whereas for persistence they include age, being off work, low back pain, and cycling.