Original article
The association between neck pain intensity, physical functioning, depressive symptomatology and time-to-claim-closure after whiplash

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Abstract

Time-to-claim-closure is a common outcome in cohort studies of whiplash injuries. However, its relationship to health recovery is unknown. We investigated the association between neck pain, physical functioning, depressive symptomatology and time-to-claim-closure in a Saskatchewan cohort of 5398 whiplash claimants in 1994–1995. Participants were surveyed five times over 1 year. In 1995, the insurance system changed from tort to no-fault, eliminating compensation for pain and suffering. Under tort, a 10-point increase in pain reduced the claim-closure rate by 13–24% while a 10-point increase in physical functioning increased it by 17%. Depressive symptomatology reduced the claim-closure rate by 37%. Under no-fault, a 10-point increase in pain reduced the claim-closure rate by 18% while a 10-point increase in physical functioning increased it by 10–35%. The presence of depressive symptomatology reduced the claim-closure rate by 36%. The results suggests lower pain, better function and the absence of depressive symptoms are strongly associated with faster time-to-claim-closure and recovery after whiplash, independent of the insurance system.

Introduction

Whiplash is an acceleration–deceleration mechanism of energy transfer to the neck that results from motor vehicle collisions. The trauma causes soft-tissue injuries to the cervical spine that may lead to clinical manifestations such as neck pain, headache and dizziness [1]. Whiplash is the most common injury following motor vehicle collisions [2]. In Canada, the incidence of auto insurance claims for whiplash varies across provinces and auto insurance legislation. In 1987, in Quebec, the incidence of whiplash claims was 70 per 100,000 inhabitants under a no-fault system (claimants cannot sue for pain and suffering) while it was 700 per 100,000 in Saskatchewan, which operated under a tort system (claimants can sue through the courts for pain and suffering) [1]. More recently, in Saskatchewan, the 6-month incidence of whiplash claims decreased from 417 to 302 per 100,000 inhabitants after the insurance system changed from tort to no-fault [2].

During the past decade, the views on whiplash have evolved from a mainly biological illness to a complex construct that is influenced by biological, psychological, social, legal and economic forces. Recent evidence indicates that the elimination of legal actions, the introduction of waiting periods and deductible amounts for reimbursement for medical treatment and the absence or elimination of disability compensation for pain and suffering significantly reduce the number of claims and improve the prognosis of whiplash injuries 1, 2, 3, 4, 5, 6. The current paradigm about the course of whiplash injuries calls for the identification of an outcome measure that incorporates claimants' health status into this broader construct of whiplash.

Time-to-claim-closure is a frequently used outcome in automobile insurance and workers' compensation studies 1, 2, 7, 8, 9. This outcome, which corresponds to the date marking the end of payments for medical treatment or income replacement benefits, is sometimes described as a proxy for time-to-recovery. However, time-to-claim-closure and time-to-recovery may not always coincide and it is possible that claimants who settle their claim still experience pain and disability after the closure date [8].

Researchers have criticized the use of time-to-claim-closure as a health status outcome because of its administrative nature, and a lack of validation studies. However, it is arguable that it may be related to health status because injury claims remain open as long as health care is provided. This argument suggests that claim-closure may correspond to maximal medical improvement and recovery.

Clinicians also criticize time-to-claim-closure for being an administrative outcome that has an uncertain association with clinically relevant outcomes such as pain and function [10]. Further, interpreting the clinical significance of time-to-claim-closure is often difficult because it depends on both patients' individual characteristics and on factors that are external to clinical recovery. Among these external factors, workplace psychosocial conditions, involvement of a lawyer, availability of modified work and heaviness of the job have been implicated 1, 2, 7, 11, 12, 13, 14, 15.

Although several studies have built prognostic models predicting time-to-claim-closure, none has yet investigated the association between health indicators of recovery and time-to-claim-closure 1, 7, 11, 12, 13, 14, 15. Two main reasons help explain this lack of research. First, no universally accepted definition of recovery exists and the definition often varies according to the stakeholder involved in the claim process. For example, patients may report recovery when their pain has disappeared, while insurers may infer recovery when maximal improvement is reached at the end of an episode of care. Second, designing a study to assess the relationship between health indicators of recovery and time-to-claim-closure is methodologically challenging. Measuring the health indicators regularly enough to provide a valid indication of a claimant's changing status is expensive and burdensome to claimants.

Because recovery from whiplash is poorly defined and under the influence of many forces, it is unclear whether time-to-claim-closure is a valid measure of recovery. The objective of our study is to prospectively quantify the strength of the association between accepted health indicators of recovery and time-to-claim-closure in a cohort of claimants with whiplash injuries. We hypothesize that lower neck pain intensity, higher functional status and the absence of significant depressive symptomatology are positively associated with faster time-to-claim-closure. Further, we hypothesize that these associations are similar under tort and no-fault auto insurance systems.

Section snippets

Methods

Saskatchewan is a Canadian province of approximately 1 million residents with a single automobile insurer, the Saskatchewan Government Insurance Company (SGI). SGI is a crown corporation that maintains a central database of all claimants. Until December 31, 1994, the automobile insurance system in Saskatchewan operated under tort legislation. However, on January 1, 1995 it changed to no-fault and compensation for pain and suffering was eliminated. The subjects included in the study were

Study sample characteristics

The sociodemographic characteristics of the claimants in each system are presented in Table 1. A higher proportion of younger individuals, males, single individuals and those with an annual family income below $20,000 claimed for whiplash under tort, while a higher proportion of full-time workers and individuals without dependents claimed under no-fault. A higher proportion of tort claimants reported that their general health was excellent before the collision, and the prevalence of

Discussion

Our results support the hypothesis that neck pain intensity, physical functioning and depressive symptomatology are associated with time-to-claim-closure after whiplash injuries. The direction of these associations indicates that throughout an episode of whiplash, higher pain intensity, poorer physical function and the presence of depressive symptomatology are related to slower claim-closure rates. Except neck pain intensity under tort, the strength of association for the other exposures

Acknowledgements

This study was supported by a grant from Saskatchewan Government Insurance and from Health Canada through the National Health Research and Development Program (grant # 6606-6599-004). The participation of Pierre Côté was made possible by a Doctoral Fellowship Training Award from Health Canada through the National Health Research and Development Program and through the Institute for Work & Health by the Workplace Safety and Insurance Board of Ontario. We thank Mrs. Diana Fedesoff for her help

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