European Spine Journal 2010 (Jun); 19 (6): 972–981 ~ FULL TEXT
Paul S. Nolet, Pierre Côté, J. David Cassidy and Linda J. Carroll
Centre of Research Expertise in Improved Disability Outcomes (CREIDO),
University Health Network Rehabilitation Solutions,
Toronto Western Hospital,
Paul S. Nolet,
86 Dawson Road, Unit 3,
Guelph, ON N1H 1A8, Canada
The objective of this population-based cohort study was to investigate the association between a lifetime history of neck injury from a motor vehicle collision and the development of troublesome neck pain. The current evidence suggests that individuals with a history of neck injury in a traffic collision are more likely to experience future neck pain. However, these results may suffer from residual confounding. Therefore, there is a need to test this association in a large population-based cohort with adequate control of known confounders.
We formed a cohort of 919 randomly sampled Saskatchewan adults with no or mild neck pain in September 1995. At baseline, participants were asked if they ever injured their neck in a motor vehicle collision. Six and twelve months later, we asked about the presence of troublesome neck pain (grade II–IV) on the chronic pain grade questionnaire. Multivariable Cox regression was used to estimate the association between a lifetime history of neck injury in a motor vehicle collision and the onset of troublesome neck pain while controlling for known confounders.
The follow-up rate was 73.5% (676/919) at 6 months and 63.1% (580/919) at 1 year. We found a positive association between a history of neck injury in a motor vehicle collision and the onset of troublesome neck pain after controlling for bodily pain and body mass index (adjusted HRR = 2.14; 95% CI 1.12–4.10).
Our analysis suggests that a history of neck injury in a motor vehicle collision is a risk factor for developing future troublesome neck pain. The consequences of a neck injury in a motor vehicle collision can have long lasting effects and predispose individuals to experience recurrent episodes of neck pain.
From the FULL TEXT Article:
Whiplash is an acceleration–deceleration mechanism of energy transfer to the neck that occurs in motor vehicle collisions [10, 24]. The trauma can lead to whiplash-associated disorders (WAD), which includes neck pain and other symptoms such as headache, dizziness, and upper extremity numbness . As many as 83% of individuals involved in traffic collisions suffer from whiplash injuries [10, 24, 26]. Consequently, WAD is a common source of pain, disability, and health care utilization in the Western world.
The recently published report of the Bone and Joint Decade 2000–2010 Task Force on Neck Pain and its Associated Disorders found that a significant proportion of patients with WAD develop persistent or recurrent neck pain. Specifically, more than 50% of patients report neck pain 1 year after their injury . Recovery from WAD is negatively associated with initial symptom severity, post-injury psychological distress, passive coping, and the intense initial health care utilization .
It has been proposed that individuals with a history of whiplash injuries are more likely to suffer from future episodes of musculoskeletal pain, including neck pain, than those without a history of whiplash injuries. This association is supported by five studies conducted in various source populations [4, 7, 11, 15, 16]. However, two Lithuanian studies of individuals sampled from police records did not support this association [18, 23]. The varying evidence reported in the literature is likely attributable to the differences in study samples, exposure and outcome definition and measurement, and to inadequate control of confounding. Therefore, there is a need for a rigorous, population-based cohort study where the association between a lifetime history of neck injury in a motor vehicle collision and future neck pain can be tested with good control of confounding factors. The objective of this study was to determine whether a lifetime history of neck injury in a motor vehicle collision is associated with an incident episode of troublesome neck pain.
Our survey was the first North American cohort study to investigate the association between a lifetime history of neck injury resulting from a motor vehicle collision and the development of troublesome neck pain. Our results suggest that the incidence of troublesome neck pain is higher in individuals who have a history of neck injury in a motor vehicle collision.
Our study has limitations. Neck pain follows a recurrent course and that risk factors for future episodes, such as motor vehicle collisions, may have a mediating effect on the incidence of pain and disability in those with a prior history of neck pain. Future studies need to test this hypothesis.
Our exposure, neck injury in a motor vehicle collision, could suffer from differential misclassification. It is possible that participants with recurrent neck pain were more likely to remember an injury in a traffic collision than those who remained free of neck pain. However, we believe that this bias had minimal impact on our results because it is likely that all participants would remember an event such as being injured in a motor vehicle collision. Data from two studies support the view that individuals can recall injuries sustained in a recent motor vehicle collision. Self-reported motor vehicle collision injuries 12 months earlier in the Canadian National Population Health Survey were not significantly different from the police reported data from Transport Canada . Moreover, in a small sample of young adults, self-reported injury over the previous 3 years was comparable to hospital discharge file data and police motor vehicle collision reports .
Our analysis of attrition suggests that the hazard rate ratio of this study could have been underestimated. A higher percentage of females responded to the follow-up surveys in the non-exposed group, and females are more likely to report neck pain than males .
There were a lower percentage of responders in the exposed group with depression at 6 months, and depression is a risk factor for the development of neck pain . Finally, in the exposed group, participants with headaches that had a moderate to severe impact on health were less likely to respond to the survey at both 6 and 12 months. Attrition varied across employment status, education, and income, but there was no clear trend in attrition to suggest that the results were biased.
Our analysis may have underestimated the true effect of neck injury in a motor vehicle collision on the development of a future episode of troublesome neck pain. It is likely that in excluding subjects with prevalent troublesome neck pain from our cohort, we excluded some subjects that had developed a new episode of troublesome neck pain (incident cases) after exposure to a motor vehicle collision but prior to the baseline survey. Excluding these cases would likely cause an underestimation of the true incidence of troublesome neck pain after a motor vehicle collision.
Our study augments the evidence of a positive association between neck injury in a motor vehicle collision and future neck pain. The strength of our study is in our ability to test for the confounding effect of more variables than prior studies, which mostly controlled for age and gender [4, 7, 15, 16, 18]. In our final model, we controlled for the effects of baseline bodily pain and the BMI. It is possible that bodily pain was in fact a mediating variable that lies on the causal pathway between the exposure to neck injury in a motor vehicle collision and the outcome of troublesome neck pain.
Our results inform the debate surrounding the etiology of neck pain in the population. Neck pain is a recurrent disorder characterized by the periods of the fluctuating pain and disability . To date, few studies have identified risk factors for the recurrent episodes of the neck pain. Our study raises the hypothesis that a past history of a neck injury in a MVC is one of the determinants of recurrent neck pain. Our analysis provides the public, clinicians, and insurers with evidence that a past neck injury in a motor vehicle collision may have a significant role in the development of future episodes of pain and disability. While the causal mechanisms linking a past history of neck injury following a motor vehicle collision and future neck pain remain unknown, it likely involves complex relationships between biological, psychological, and social factors. Future research needs to focus on elucidating these mechanisms within the biopsychosocial model of health.