[Whiplash in insurance medicine: lessons for physicians]. / Whiplash in de verzekeringsgeneeskunde.

The number of employees applying for a labour disability benefit due to whiplash has gradually decreased during the last 25 years in the Netherlands. The total number of applicants seems to stabilise around 30% of the number around the turn of the century. This is surprising given that the professional standards for social insurance physicians emphasise the importance of rehabilitation, while courts hardly ever judge in favour of benefit claimants. We investigate the underlying reasons for the changing statistics and make a recommendation on how social insurance physicians can best approach a claimant.

Long-term follow-up of whiplash injuries reported to insurance companies: a cohort study on patient-reported outcomes and impact of financial compensation.

PURPOSE: The long-term outcome of Whiplash-associated disorder (WADs) has been reported to be poor in populations from medical settings. However, no trials have investigated the long-term prognosis of patients from medico-legal environment. For this group, the "compensation hypothesis" suggests financial compensation being associated with worsened outcome. The aims of this study were to describe long-term (2-4 years) non-recovery rates in participants with WAD recruited from insurance companies and to investigate the association between self-reported non-recovery and financial compensation. METHODS: 144 participants, reporting neck pain after a motor vehicle accident, were recruited from two major insurance companies in Sweden. Self-reported recovery was measured at 6 months and 2-4 years. Those who received financial compensation from an insurance company were compared with those who received no compensation. RESULTS: The overall non-recovery rate after 2-4 years was 55.9% (66/118). In the non-compensated group, the non-recovery rate was 51.0% (25/49) and in the compensated group 73% (27/37) (p = 0.039). Adjusted OR was 4.33 (1.37-13.66). High level of pain at baseline was a strong predictor of non-recovery [OR 46 (4.7-446.0)]. However, no association was found between pain level at baseline and financial compensation. CONCLUSIONS: The non-recovery rate among patients making insurance claims is high, especially among those receiving financial compensation even if causal relationship cannot be determined based on this study. However, lack of association between baseline level of pain and compensation supports the compensation hypothesis.

The Nature of Whiplash in a Compensable Environment: Injury, Disability, Rehabilitation, and Compensation Systems.

Synopsis Whiplash is a compensable injury in many jurisdictions, but there is considerable heterogeneity in the compensation arrangements that apply across jurisdictions, even within some countries. These compensation schemes have, however, been subject to a common set of interrelated concerns, chiefly concerning the incentives, behaviors, and outcomes that may arise when financial compensation for injuries is available to injured parties. This article provides a nontechnical overview of some of those concerns through the lens of economics: principally, insurance economics and health economics, including related subsets such as information economics and agency theory, as well as economics and the law. It notes that because it is generally infeasible to randomize the treatment (ie, compensation) via trials, analyses of observational data are necessary to discover more about the relationship between compensation and health outcomes. This poses the analytical challenge of discovering causal connections between phenomena from nonrandomized data sets. The present article calls for further research that would enable convincing causal interpretations of such relationships via the careful analysis of rich observational data sets using modern econometric methods. J Orthop Sports Phys Ther 2017;47(7):503-508. Epub 16 Jun 2017. doi:10.2519/jospt.2017.7533.

Cost-effectiveness of neck-specific exercise with or without a behavioral approach versus physical activity prescription in the treatment of chronic whiplash-associated disorders: Analyses of a randomized clinical trial.

BACKGROUND: Fifty percent of people injured by whiplash still report neck pain after 1 year and costs associated with whiplash associated disorders (WAD) are mostly attributed to health service and sick-leave costs in chronic conditions. With increasing health care expenditures the economic impact of interventions needs to be considered. OBJECTIVE: To analyze the cost-effectiveness of physiotherapist-led neck-specific exercise without (NSE) or with a behavioral approach (NSEB), or prescription of physical activity (PPA) in chronic WAD, grade 2 to 3. METHODS: This is a secondary cost-effectiveness analysis of a multicenter randomized clinical trial of 216 participants with chronic WAD grade 2 to 3. The interventions were physiotherapist-led neck-specific exercise without or with a behavioral approach, or prescription of physical activity for 12 weeks. Incremental cost-effectiveness ratios (ICERs) were determined after 1 year and bootstrapped cost-effectiveness planes and sensitivity analyses of physiotherapy visits were performed. Health care and production loss costs were included and quality-adjusted life years (QALYs) were estimated, using the Euroqol-5D questionnaire. Comparisons with the Short Form-6D, and neck disability index (NDI) were also made. RESULTS: The 1-year follow-up was completed by 170 participants (79%). Both physiotherapist-led groups improved in health related quality of life. The intervention cost alone, per quality-adjusted life year (QALY) gain in the NSE group was US$ 12,067. A trend for higher QALY gains were observed in the NSEB group but the costs were also higher. The ICERs varied depending on questionnaire used, but the addition of a behavioral approach to neck-specific exercise alone was not cost-effective from a societal perspective (ICER primary outcome $127,800 [95% confidence interval [CI], 37,816-711,302]). The sensitivity analyses confirmed the results. The prescription of physical activity did not result in any QALY gain and the societal costs were not lower. CONCLUSION: Neck-specific exercise was cost-effective from a societal perspective in the treatment of chronic WAD compared with the other exercise interventions. ICERS varied depending on health-related quality of life questionnaires used, but the addition of a behavioral approach was not cost-effective from a societal perspective. The prescription of physical activity did not result in any QALY gain and was thus not considered a relevant option.

The relationship between insurance claim closure and recovery after traffic injuries for individuals with whiplash associated disorders.

PURPOSE: The purpose of this study was to determine if time to claim closure was similar to time to self-reported recovery in a no fault motor vehicle collision insurance system. METHOD: A prospective cohort of traffic injured adults with a whiplash-associated disorder (WAD) was assembled. We excluded participants who applied for benefits after 42 days of the collision, who were in hospital for more than two days and participants who were not followed up at least once after their injury. Questionnaires were completed at baseline, six weeks, three-, six-, nine- and 12-months after the collision. RESULTS: The mean age of the cohort was 39 years and 66% were female. The mean number of days until claim closure and for self-reported recovery was 291days and 134 days, respectively. We found those who had their claim closed at each follow-up period had lower levels of disability and were more likely to report they were recovered than participants with open claims. CONCLUSION: We conclude that time to claim closure could be used as an outcome measure in traffic collision; however, this measure should be used with caution since it over-estimates the true time to recovery. Implications for Rehabilitation Time to claim closure as an outcome measure for whiplash-associated disorders has been criticized in the literature because it is thought that closure is not reflective of the health status of the individual. We found that claim closure was associated with lower levels of disability, but the time to claim closure was significantly longer than the time to self-reported recovery. Time to claim closure may be used with caution as a "proxy" measure of recovery from an injury; however, it must be noted that it over-estimates the true time of recovery.

Economic and Health-Related Quality of Life Outcomes of Whiplash Associated Disorders.

STUDY DESIGN: This study examines the links between severity of whiplash associated disorder and costs and health outcomes. OBJECTIVE: The study aims to estimate the economic costs and health-state utilities associated with disability levels and recovery trajectories after acute whiplash injury. SUMMARY OF BACKGROUND DATA: Data used were from the Managing Injuries of the Neck Trial, which collected information on 3851 people over a 12-month period after acute whiplash injury. METHODS: Effects of whiplash associated disorder severity on economic costs (measured from a societal perspective and separately from a health and personal social services perspective) were estimated using two-part regression models, comprising probability of incurring a cost and the total cost, given one was incurred. Effects on health-state utilities (measured using the EQ-5D and SF-6D) were estimated using ordinary least squares regression, and two-part models as for costs. RESULTS: There was a direct relationship between severity of disability after acute whiplash injury and economic costs. Between baseline and 4 months, average societal costs for those with no disability were £99.55 (UK£, 2009 prices), increasing to £668.53 for those with complete disability. Average societal costs for the whole sample were £234.15 over the first 4 months, decreasing to £127.51 between 8 and 12 months. Conversely, utility scores decreased with increased disability. The average EQ-5D utility score was 0.934 at 4 months for those with no disability, decreasing to 0.033 for those with complete disability. The average EQ-5D utility score for the whole sample increased from 0.587 immediately post-injury to 0.817 at 12 months. Relative costs and disutilities generated by the multivariate models are also presented by disability level and recovery trajectory. CONCLUSION: These results provide estimates of the costs and health-state utilities associated with disability levels and recovery trajectories after acute whiplash injury. They can be used to inform estimates of the cost-effectiveness of interventions targeting whiplash-associated disorders. LEVEL OF EVIDENCE: 3.

How does injury compensation affect health and disability in patients with complaints of whiplash? A qualitative study among rehabilitation experts-professionals.

PURPOSE: To explore rehabilitation professionals' opinions about the influence and the pathways of injury compensation (IC) on health and disability in patients with whiplash associated disorder (WAD). METHODS: Semi-structured interviews were performed among a purposeful selected sample of Dutch expert-professionals in the field of rehabilitation of patients with WAD. Inclusion continued until saturation was reached. Inductive and deductive thematic analyses were performed. RESULTS: Ten rehabilitation expert-professionals (five females), working as physician, psychologist or physiotherapist, were interviewed. All expert-professionals acknowledged that IC can influence rehabilitation, health and disability. The expert-professionals provided three causal pathways; a pathway through prolonged distress, a behavioral pathway, and patient characteristics that may either attenuate or worsen their response. They assess the influence of IC mainly with interview techniques. Most professionals discuss the potential influence of IC with their patients, because they want to give clear information to the patient. Some emphasize that their role is neutral in relation with the IC. Others mention that financial consequences can accompany functional improvement. CONCLUSIONS: Rehabilitation expert-professionals believe that IC may affect rehabilitation, health and disability in patients with WAD. Three pathways are mentioned by the experts-professionals. IMPLICATIONS FOR REHABILITATION: According to rehabilitation expert-professionals, an injury compensation (IC) can lead to distress, by creating a (conscious or unconscious) conflict of interests within a patient between striving for compensation on one hand, and recovery on the other hand. Patient characteristics can either attenuate or worsen IC-related distress. Reliable and valid tools need to be developed to assess the influence of IC on health, disability and rehabilitation, and to limit the negative effects. Rehabilitation professionals can discuss the possible unintended effects of IC with their patients to clarify their current situation.

Course of recovery for whiplash associated disorders in a compensation setting.

CONTEXT: The detailed course of recovery following compensable whiplash associated disorders (WAD) is not well understood. Some people recover within months and others report symptoms for extended periods. Recent research identified distinct recovery pathways. Identifying recovery pathways for people with this condition in compensable settings could assist clinical and claim management. STUDY OBJECTIVE: This study aimed to identify recovery trajectories based on disability, pain catastrophising and mental health and, secondly, to examine developmental linkages between the trajectories. STUDY DESIGN: A cohort of 246 people with compensable WAD were followed for 24 months after a motor vehicle related injury. OUTCOME MEASURES: Functional Rating Index (FRI), Pain Catastrophising Scale (PCS) and the SF36 Mental Component Score (SF 36 MCS). METHOD: Group-based trajectory analytical techniques were used to identify distinct post-injury profiles. Multinominal logistic regression modelling identified factors associated with membership of different trajectories. RESULTS: 246 people were enrolled a median of 72 days after injury. Three trajectories were identified for the measures used and their prevalences, respectively, were: for disability (FRI) they were mild (47%), moderate (31%), and severe (22%); for pain catastrophising (PCS) they were non-catastrophisers (55%), moderate-low catastrophisers (32%) and clinically significant catastrophisers (13%); and, for mental health (SF36 MCS) they were good mental health (40%), moderately low mental health (42%) and severely low mental health (18%). All groups showed no further recovery beyond 12 months after injury. The significant baseline predictors of the severe disability trajectory were: lower (that means worse) bodily pain scores (SF 36 BPS) (p≤0.01); high pain catastrophising (p≤0.01); and, self-reported fair or poor general health (p=0.03). Conditional probabilities for group membership showed that the three trajectories for both PCS and FRI were linked. Dual membership was high for the mild disability and mild pain catastrophising trajectories and, for the severe disability and clinically significant pain catastrophising trajectories. CONCLUSIONS: There is a strong and plausible association between severe disability, clinical levels of pain catastrophising and low mental health. Claimants can be identified at claim notification based on three estimated recovery trajectories. Claim and clinical interventions can be targeted to the profile within each recovery trajectory.

Associations with duration of compensation following whiplash sustained in a motor vehicle crash.

CONTEXT: Continued exposure to compensation systems has been reported as deleterious to the health of participants. Understanding the associations with time to claim closure could allow for targeted interventions aimed at minimising the time participants are exposed to the compensation system. STUDY OBJECTIVE: To identify the associations of extended time receiving compensation benefits with the aim of developing a prognostic model that predicts time to claim closure. STUDY DESIGN: Prospective cohort study in people with whiplash associated disorder. OUTCOME MEASURES: Time to claim closure, in a privately underwritten fault based third party traffic crash insurance scheme in New South Wales, Australia. METHOD: Cox proportional hazard regression modelling. RESULTS: Of the 246 participants, 25% remained in the compensation system longer than 24 months with 15% remaining longer than three years. Higher initial disability (Functional Rating Index≥25 at baseline) (HRR: 95% CI, 1.916: 1.324-2.774, p<0.001); and lower initial mental health as measured by SF-36 Mental Component Score (HRR: 95% CI, 0.973: 0.960-0.987, p<0.001) were significantly and independently associated with an increased time-to-claim closure. Shorter time to claim closure was associated with having no legal involvement (HRR: 95% CI, 1.911: 1.169-3.123, p=0.009); and, not having a prior claim for compensation (HRR: 95% CI, 1.523: 1.062-2.198, p=0.022). CONCLUSIONS: Health and insurance related factors are independently associated with time to claim closure. Both factors need to be considered by insurers in their assessment of complexity of claims. Interventions aimed at minimising the impact of these factors could reduce claimants' exposure to the compensation system. In turn insurers can potentially reduce claims duration and cost, while improving the health outcomes of claimants.

Associations with legal representation in a compensation setting 12 months after injury.

CONTEXT: Many people with Whiplash Associated Disorder (WAD) seek treatment though a compensation system where factors such as legal involvement have been reported as having a negative impact on recovery outcomes. OBJECTIVE: To compare those with and without legal involvement in their compensation claim, and identify associations with legal involvement at 12 months post injury; and longer term disability. STUDY DESIGN: Inception cohort study. PARTICIPANTS: 246 people with WAD compensation claim. OUTCOME MEASURES: Legal involvement and Functional Rating Index at 12 months post injury. METHODS: Participants were recruited from an insurance database. Baseline health (Functional Rating Index, Pain Catastrophising Scale and SF-36), socio-economic, work capacity, and claims data were collected within three months of injury and 12 months. Logistic regression models were used to identify associations with legal involvement at 12 months; and disability (FRI) at 12 months. RESULTS: At baseline 246 participants were enrolled into the study in a median 72 days post injury. At 12 months post injury 52 (25%) had engaged a lawyer. The significant independent associations with legal involvement at 12 months were higher levels of initial disability, work disability, speaking a language other than English at home and lower levels of mental health. Specifically, the odds of lawyer involvement at 12 months post injury was 4.9 times greater for those with work disability; 2.3 times greater for those who spoke a language other than English at home. In terms of health, they had poorer mental health and for every 10 unit increase in the baseline FRI score the odds of having lawyer involvement increased by 38%. DISABILITY: at 12 months (FRI) was significantly independently associated with, PCS-helplessness (p<0.001), age (p<0.001) and prior claim (p=0.001). CONCLUSION: This study suggests the people with lawyer involvement in their claim 12 months after injury have socio-economic disadvantage, have had a prior claim and a worse baseline health profile compared to those without a lawyer. Understanding this profile could allow for improved claims processes and targeted interventions to assist this group through any perceived complexities in the system and address the underlying reasons for lawyer participation within compensation schemes.

Modic changes of the cervical spine in patients with whiplash injury: a prospective 11-year follow-up study.

INTRODUCTION: There are few studies on Modic changes of the cervical spine in patients suffering from whiplash. This study compared Modic changes seen in whiplash patients 10 years after the injury with those observed in asymptomatic volunteers. METHODS: This is a follow-up study of 133 patients who suffered whiplash injuries in 1994-1996 and underwent MRI with a superconductive imager (63 men, 70 women, mean age 49.6±15.3 years, mean follow-up 11.4 years). In addition, 223 healthy volunteers who underwent MRI during the same period were included as controls (123 men, 100 women, mean age 50.5±15.0 years, mean follow-up 11.6 years). All participants underwent follow-up MRI. We examined all participants for Modic changes, and investigated relationships between Modic changes and clinical symptoms or potentially related factors. RESULTS: Modic changes were observed in 4 patients (3%) and at 7 intervertebral levels in the initial study, and in 17 patients (12.8%) and at 30 intervertebral levels at the follow-up. Modic Type 2 changes were the most prevalent in the whiplash patients in both the initial and follow-up studies. There was no significant difference in the percentage of whiplash patients versus control subjects with positive Modic changes, either at the initial study or at follow-up. Modic changes were not related to clinical symptoms present at follow-up, but were associated with preexisting disc degeneration. There was no association between Modic changes and the details of the car accident that caused the injury. CONCLUSIONS: While Modic changes became more common in whiplash patients in the 10-year period after the accident, they occurred with a similar frequency in control subjects. We did not find any association between Modic changes and the nature of the car accident in which the whiplash occurred. Modic changes found in whiplash patients may be a result of the physiological ageing process rather than pathological findings relating to the whiplash injury.

Managing Injuries of the Neck Trial (MINT): a randomised controlled trial of treatments for whiplash injuries.

OBJECTIVES: To examine the clinical effectiveness of a stepped care approach over a 12-month period after an acute whiplash injury; to estimate the costs and cost-effectiveness of each strategy including treatments and subsequent health-care costs; and to gain participants' perspective on experiencing whiplash injury, NHS treatment, and recovery within the context of the Managing Injuries of the Neck Trial (MINT). DESIGN: Two linked, pragmatic, randomised controlled trials. In Step 1, emergency departments (EDs) were cluster randomised to usual care advice (UCA) or The Whiplash Book advice (WBA)/active management advice. In Step 2, participants were individually randomised to either a single session of advice from a physiotherapist or a physiotherapy package of up to six sessions. An economic evaluation and qualitative study were run in parallel with the trial. SETTING: Twelve NHS trusts in England comprising 15 EDs. PARTICIPANTS: People who attended EDs with an acute whiplash injury of whiplash-associated disorder grades I-III were eligible for Step 1. People who had attended EDs with whiplash injuries and had persistent symptoms 3 weeks after ED attendance were eligible for Step 2. INTERVENTIONS: In Step 1, the control intervention was UCA and the experimental intervention was a psycho-educational intervention (WBA/active management advice). In Step 2 the control treatment was reinforcement of the advice provided in Step 1 and the experimental intervention was a package of up to six physiotherapy treatments. MAIN OUTCOME: The primary outcome was the Neck Disability Index (NDI), which measures severity and frequency of pain and symptoms, and a range of activities including self-care, driving, reading, sleeping and recreation. Secondary outcomes included the mental and physical health-related quality-of-life (HRQoL) subscales of the Short Form questionnaire-12 items (SF-12) and the number of work days lost. RESULTS: A total of 3851 patients were recruited to Step 1 of the trial. 1598 patients attending EDs were randomised to UCA, and 2253 were randomised to WBA/active management. Outcome data were obtained at 12 months for 70% and 80% of participants at Step 1 and Step 2, respectively. The majority of people recovered from the injury. Eighteen per cent of the Step 1 cohort had late whiplash syndrome. There was no statistically or clinically significant difference observed in any of the outcomes for participants attending EDs randomised to UCA or active management advice [difference in NDI 0.5, 95% confidence interval (CI) -1.8 to 2.8]. In Step 2 the physiotherapy package resulted in improvements in neck disability at 4 months compared with a single advice session, but these effects were small at the population level (difference in NDI -3.2, 95% CI -5.8 to -0.7). The physiotherapy package was accompanied by a significant reduction in the number of work days lost at 4-month follow-up (difference -40.2, 95% CI -44.3 to -35.8). CONCLUSIONS: MINT suggests that enhanced psycho-educational interventions in EDs are no more effective than UCA in reducing the burden of acute whiplash injuries. A physiotherapy package provided to people who have persisting symptoms within the first 6 weeks of injury produced additional short-term benefits in neck disability compared with a single physiotherapy advice session. However, from a health-care perspective, the physiotherapy package was not cost-effective at current levels of willingness to pay. Both experimental treatments were associated with increased cost with no discernible gain in health-related quality of life. However, an important benefit of the physiotherapy package was a reduction in work days lost; consequently, the intervention may prove cost-effective at the societal level. TRIAL REGISTRATION: Current Controlled Trials ISRCTN33302125. FUNDING: This project was funded by the NIHR Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 16, No. 49. See the HTA programme website for further project information.

Are people who claim compensation "cured by a verdict"? A longitudinal study of health outcomes after whiplash.

This study examines whether the lure of injury compensation prompts whiplash claimants to overstate their symptoms. Claim settlement is the intervention of interest, as it represents the point at which there is no further incentive to exaggerate symptoms, and neck pain at 24 months is the outcome of interest. Longitudinal data on neck pain scores and timing of claim settlement were regressed, controlling for the effect of time on recovery, to compare outcomes in claimants who had and had not settled their compensation claims. The results show clearly that removing the financial incentive to over-report symptoms has no effect on self-reported neck pain in a fault-based compensation scheme, and this finding concurs with other studies on this topic. Policy decisions to limit compensation in the belief that claimants systematically misrepresent their health status are not supported empirically Claimants do not appear to be "cured by a verdict".

Research on injury compensation and health outcomes: ignoring the problem of reverse causality led to a biased conclusion.

OBJECTIVE: This study highlights the serious consequences of ignoring reverse causality bias in studies on compensation-related factors and health outcomes and demonstrates a technique for resolving this problem of observational data. STUDY DESIGN AND SETTING: Data from an English longitudinal study on factors, including claims for compensation, associated with recovery from neck pain (whiplash) after rear-end collisions are used to demonstrate the potential for reverse causality bias. Although it is commonly believed that claiming compensation leads to worse recovery, it is also possible that poor recovery may lead to compensation claims--a point that is seldom considered and never addressed empirically. This pedagogical study compares the association between compensation claiming and recovery when reverse causality bias is ignored and when it is addressed, controlling for the same observable factors. RESULTS: When reverse causality is ignored, claimants appear to have a worse recovery than nonclaimants; however, when reverse causality bias is addressed, claiming compensation appears to have a beneficial effect on recovery, ceteris paribus. CONCLUSION: To avert biased policy and judicial decisions that might inadvertently disadvantage people with compensable injuries, there is an urgent need for researchers to address reverse causality bias in studies on compensation-related factors and health.

Does injury compensation lead to worse health after whiplash? A systematic review.

One might expect that injury compensation would leave injured parties better off than they would otherwise have been, yet many believe that compensation does more harm than good. This study systematically reviews the evidence on this "compensation hypothesis" in relation to compensable whiplash injuries. PubMed, CINAHL, EMBASE, PEDro, PsycInfo, CCTR, Lexis, and EconLit were searched from the date of their inception to April 2010 to locate longitudinal studies, published in English, comparing the health outcomes of adults exposed/not exposed to compensation-related factors. Studies concerning serious neck injuries, using claimants only, or using proxy measures of health outcomes were excluded. Eleven studies were included. These examined the effect of lawyer involvement, litigation, claim submission, or previous claims on pain and other health outcomes. Among the 16 results reported were 9 statistically significant negative associations between compensation-related factors and health outcomes. Irrespective of the compensation-related factor involved and the health outcome measured, the quality of these studies was similar to studies that did not find a significant negative association: most took some measures to address selection bias, confounding, and measurement bias, and none resolved the potential for reverse causality bias that arises in the relationship between compensation-related factors and health. Unless ambiguous causal pathways are addressed, one cannot draw conclusions from statistical associations, regardless of their statistical significance and the extent of measures to address other sources of bias. Consequently, there is no clear evidence to support the idea that compensation and its related processes lead to worse health.

Delayed recovery in patients with whiplash-associated disorders.

BACKGROUND: Prognosis of whiplash injury has been found to be related to a number of sociodemographic, treatment and clinical factors. In the current study, we attempt to identify several novel prognostic factors for delayed recovery in whiplash-associated disorders (WADs), using a validated and reliable measure of recovery. PATIENTS AND METHODS: Retrospective review of a large database of a national network of physiotherapy and rehabilitation service providers in Canada yielded 5581 individuals injured in motor vehicle collisions. Cases were grouped into 3 cohorts based on time lapsed between injury date and initial presentation. Acute (n=3075), early chronic (n=958) and chronic (n=1548) patient cohorts were compared regarding treatment outcome and relative distribution of 29 prognostic factors. Outcome was defined by a minimally important clinical change (10%) on a previously validated disability questionnaire between initial and discharge rehabilitation visits. RESULTS: Analysis demonstrated positive outcomes to be proportionally fewer in the chronic cohort (52.1%) relative to the early chronic (61.4%), which was in turn lower than the acute cohort (72.3%). Furthermore, individuals presenting with chronic pain were more likely to: (1) be female; (2) present with lower limb pain or nonorganic signs; (3) have returned to work; (4) have retained a lawyer; or (5) have undergone previous spinal surgery, and were less likely to: (1) present with neck or midback pain; (2) live in Ontario or Nova Scotia; or (3) have modified duties upon return to work. Acute, early chronic and chronic cohorts were also found to differ in the distribution of several other prognostic factors at initial clinical visit. CONCLUSIONS: Recovery in whiplash-associated disorder appears to be multifactorial with both medical and non-injury related factors influencing outcome. Further characterisation of these factors may prove invaluable in guiding future clinical treatment and referral practices.

Whiplash and the compensation hypothesis.

STUDY DESIGN: Review article. OBJECTIVE: To explain why the evidence that compensation-related factors lead to worse health outcomes is not compelling, either in general, or in the specific case of whiplash. SUMMARY OF BACKGROUND DATA: There is a common view that compensation-related factors lead to worse health outcomes ("the compensation hypothesis"), despite the presence of important, and unresolved sources of bias. The empirical evidence on this question has ramifications for the design of compensation schemes. METHODS: Using studies on whiplash, this article outlines the methodological problems that impede attempts to confirm or refute the compensation hypothesis. RESULTS: Compensation studies are prone to measurement bias, reverse causation bias, and selection bias. Errors in measurement are largely due to the latent nature of whiplash injuries and health itself, a lack of clarity over the unit of measurement (specific factors, or "compensation"), and a lack of appreciation for the heterogeneous qualities of compensation-related factors and schemes. There has been a failure to acknowledge and empirically address reverse causation bias, or the likelihood that poor health influences the decision to pursue compensation: it is unclear if compensation is a cause or a consequence of poor health, or both. Finally, unresolved selection bias (and hence, confounding) is evident in longitudinal studies and natural experiments. In both cases, between-group differences have not been addressed convincingly. CONCLUSION: The nature of the relationship between compensation-related factors and health is unclear. Current approaches to testing the compensation hypothesis are prone to several important sources of bias, which compromise the validity of their results. Methods that explicitly test the hypothesis and establish whether or not a causal relationship exists between compensation factors and prolonged whiplash symptoms are needed in future studies.