Course and prognostic factors of whiplash: a systematic review and meta-analysis.

We conducted a systematic review and meta-analysis of prospective cohort studies of subjects with acute whiplash injuries. The aim was to describe the course of recovery, pain and disability symptoms and also to assess the influence of different prognostic factors on outcome. Studies were selected for inclusion if they enrolled subjects with neck pain within six weeks of a car accident and measured pain and/or disability outcomes. Studies were located via a sensitive search of electronic databases; Medline, Embase, CINAHL, Cochrane database, ACP Journal club, DARE and Psychinfo and through hand-searches of relevant previous reviews. Methodological quality of all studies was assessed using a six item checklist. Sixty-seven articles, describing 38 separate cohorts were included. Recovery rates were extremely variable across studies but homogeneity was improved when only data from studies of more robust methodological quality were considered. These data suggest that recovery occurs for a substantial proportion of subjects in the initial 3 months after the accident but after this time recovery rates level off. Pain and disability symptoms also reduce rapidly in the initial months after the accident but show little improvement after 3 months have elapsed. Data regarding the prognostic factors associated with poor recovery were difficult to interpret due to heterogeneity of the techniques used to assess such associations and the way in which they are reported. There was also wide variation in the measurement of outcome and the use of validated measures would improve interpretability and comparability of future studies.