Risk Factors of Whiplash, Chronic Pain

A number of studies have been published that help us understand which patients may be at a greater risk of long-term problems from whiplash injuries. The following is a summary of these new findings.

Generalized Pain

Some patients experience a car crash and suffer minor and localized symptoms; a substantial minority of patients, however, experience symptoms that don't resolve, and may even spread to other parts of the body. This generalized pain pattern has been recognized as a risk factor by numerous studies, and a current study looked specifically at this issue.

In this study by Peolsson et al.¹, the authors examined 275 whiplash patients with chronic pain. They gave each patient a battery of pain, psychological, and disability surveys and recorded the number of painful regions that each patient reported.

“According to the present cross-sectional study, widespread pain in chronic WAD is associated with negative consequences with respect to pain intensity, prevalence of other symptoms (including depressive symptoms), some aspects of coping, life satisfaction/quality and general health. Our results indicate that, in different ways, the subgroup with widespread pain had a more fragile life situation than those with more local or regional WAD. Based on our results, we argue that a preventive perspective might be urgent and that clinical rehabilitation requires a broad assessment of the spread of pain, cognitive, and neuropsychological symptoms, and depressivity and catastrophizing thoughts or strategies.”

Central Nervous System Hypersensitivity

CNS hypersensitivity is related to generalized pain, but this recent report by Jull et al.² examined the patients much more thoroughly, and specifically studied those patients with elevated pressure pain threshold or cold hyperalgesia tests. These two tests are useful in detecting an underlying central nervous system “overstimulation” that can occur in some whiplash patients.

In this study, 71 patients with whiplash were given two different treatments; one group was treated with physiotherapy and the other was given a self-management program.

The authors found that the physiotherapy group had more improvement, but “that relief was marginal in the subgroup with both widespread mechanical and cold hyperalgesia.” This study reinforces the idea that those with wider CNS responses to injury are more resistant to effective treatment.
Occupation and Arm and Shoulder Symptoms

Another new study³ looked at what factors influenced recovery in patients who were involved in litigation after their injury. 134 patients were interviewed an average of 11 months after their injury. The authors found the following:

• Patients who experienced “arm pain, upper limb numbness or paraesthesia and bilateral trapezius pain” were more likely to experience long-term problems than those who did not.
• Patients who had jobs that were more physically demanding were more likely to recover early. This is consistent with the previous literature that speculates that those patients with smaller muscle mass (in particular, women) are more likely to be injured than those with larger muscle mass.
• Not surprisingly, this study also found that patients with long-term symptoms were also more likely to seek out physiotherapy treatment of their injuries.

Body Mass Index Not Related to Recovery

This Canadian study⁴ looked at the medical records 4,395 whiplash patients between 1994 and 1995; 87.7% of these individuals had recovered by November 1997.

“In the current study, body mass index was not associated with delayed recovery from whiplash injury. Compared with individuals who were normal weight, participants who were underweight, overweight, or obese had similar rates of recovery. The results challenge the view that being overweight or obese is a risk factor for chronic pain and disability following whiplash injuries.”
Peolsson M, Borsbo B, Gerle B. Generalized pain is associated with more negative consequences than local or regional pain: a study of chronic whiplash-associated disorder. Journal of Rehabilitation Medicine 2007;39:260-268.

1. Jull G, Sterling M, Kenardy J, Beller E. Does the presence of sensory hypersensitivity influence outcomes of physical rehabilitation for chronic pain? A preliminary RCT. Pain 2007;129:28-34.
2. Karnezis IA, Drosos GI, Kazakos KI. Factors affecting the timing of recovery from whiplash neck injuries: study of a cohort of 134 patients pursuing litigation. Archives of Orthopeadic and Trauma Surgery 2007;May 9.
3. Yang X, Cote P, Cassidy JD, Carroll L. Association between body mass index and recovery from whiplash injuries: a cohort study. American Journal of Epidemiology 2007;165(9):1063-1069.