Epidemiological aspects on pain in whiplash-associated disorders

Sammanfattning: Introduction: Whiplash-associated disorders (WAD) are common after car collisions. Little is known about risk factors for onset of the injury or about factors influencing the recovery. Objective: The general objective of this thesis was to assess the influence of psychosocial factors on pain and disability in WAD. The aim of papers I and II was to assess the associations between pre-injury factors and neck pain intensity within 30 days of a motor vehicle collision. The aims of paper II were to assess the incidence and course of widespread pain in persons with WAD and to investigate factors associated with the onset of widespread pain. The aim of paper IV was to assess if injured persons´ expectations for recovery are a prognostic factor for recovery from WAD. Materials and Methods: The thesis is based on two populations of insurance claimants who have reported WAD as a result of being vehicle occupants in traffic collisions. Participants answered questionnaires at baseline and at several follow-up periods. The follow-up times differed depending on the study population. The definition of WAD was based on neck injury specific items in the questionnaires. Papers I and II are based on injury claimants from Saskatchewan, Canada and include persons injured between July 1, 1994 and December 31, 1995. Paper I includes baseline information on 5,970 persons. Pain intensity was measured with a visual analogue scale 0-100 mm (VAS), and was categorized into mild, moderate, and severe pain. Paper II includes 266 persons who reported localized spinal pain at baseline and responded to at least one of the follow-up questionnaires at six weeks, four, eight, and 12 months. The identification of cases with widespread pain was based on pain drawings completed at the follow up. Papers III and IV are based on a Swedish cohort including persons injured between January 15, 2004 and January 12, 2005, who filed a claim to either of two insurance companies. Paper III includes baseline information on 1,187 persons. Pain intensity was measured with the VAS 0-100 mm, and categorized in the same way as in paper I. Paper IV includes 1,032 persons, who did not have a full recovery when they responded to the baseline questionnaire and who were successfully followed. Disability due to pain was measured with the Pain Disability Index at follow up. Results and Conclusions: Neck pain intensity within the first month after WAD was influenced by several factors, in addition to the physical injury. Female gender, low socio- economic status, and poor prior health were associated with more severe pain intensity. In addition, having the head rotated or not knowing the head position at the time of collision was associated with more severe pain (Papers I and III). Subsequent widespread pain mostly occurred soon after the injury (Paper II). Continuous widespread pain was rare, even though 21% report such condition at some point over a one-year follow-up period. Depressive mood, intense neck pain, having several associated symptoms, and having more than three of five anatomic regions in pain early after the injury were all associated with the onset of widespread pain (Paper II). Those who thought they were less likely to make a full recovery after the injury were at higher risk to have moderate or severe disability at the follow up, compared to those who thought they were very likely to make a full recovery (Paper IV). In summary, the results indicate that pain and disability in persons with WAD are influenced by psychosocial factors at various time points after the injury. In the early management of persons with WAD it is important to consider psychological status, expectations for recovery, and social circumstances in addition to the biomedical components of the injury.