Academic journal article Bulletin of the World Health Organization

Differences in Prevalence of Pre-Existing Morbidity between Injured and Non-Injured Populations

Academic journal article Bulletin of the World Health Organization

Differences in Prevalence of Pre-Existing Morbidity between Injured and Non-Injured Populations

Article excerpt


WHO has predicted that injury will be the second leading cause of the world disease burden by the year 2020 (1, 2). A limitation in the current process of deriving population estimates of the burden attributable to injury is the failure to take into account pre-existing morbidity. If injured people differ from the general population in terms of pre-existing morbidity, then observed outcomes in injured samples that are attributed to injury may in part be due to pre-existing morbidities rather than to the injury in question.

The Australian Burden of Disease study acknowledged the importance of co-existing conditions in estimating the attributable burden of particular conditions (3). Mathers et al. (3) concluded that several methodological issues relating to comorbidity remain to be addressed if burden of disease models are to be advanced. These issues include how comorbidities affect long-term disability; which comorbidities are relevant; and how to deal with the logistics of modelling large numbers of combinations of comorbidities (3).

Although some attempts have been made to look at differences in health status in patients pre- and post-injury using self-reported retrospective recall (4), investigators using this method acknowledge inevitable biases (5 9). Bias is better managed by ascertaining pre-injury morbidity at a point in time before the injury was sustained. Although rare in injury outcome studies (10, 11), the use of comorbidity indices based on administrative claims data recorded prior to the index event is well established in other fields of research such as cancer, cardiovascular disease and diabetes (12-14).

Global burden of disease estimates currently assume that the distribution of morbidity in the community is independent of injury status. Outcome studies of clinical case series cannot test this assumption and few population-based studies that compare injured and non-injured people have been reported in the literature (10). The present study used administrative health databases to compare the frequency and distribution of morbidity in people in the 12 months prior to their sustaining an injury with the health status of the general non-injured population.


Study design

The study described in this paper is an examination of tile prevalence of pre-existing disease in two samples drawn from administrative health data from Manitoba, Canada. The two samples were originally identified on the basis of exposure to injury, for the purposes of conducting a matched, population-based retrospective cohort stud> with a follow-up period of 10 years. The University of Manitoba Research Ethics Board and the Health Information Privacy Committee of Manitoba Health approved this study. Data extractions were completed by Manitoba Health and all identifying variables were removed from the data before the study investigator was granted access to them.

Data sources

The province of Manitoba provides universal health-care coverage for a population of 1.14 million residents (15). Manitoba Health maintains databases of claims made by health providers for reimbursement of services (hospital, physician and extended-care services), as well as a population registry of those eligible for health coverage (16). Virtually every resident of Manitoba is covered by the provincial health-care plan (15). The databases have been used extensively in health research and are described in detail elsewhere (17, 18).

Setting and participants

A cohort of injured people (n = 21 032) was identified as all persons aged 18-64 years resident in the province of Manitoba, who had been hospitalized for treatment of an injury between 1 January 1988 and 31 December 1991. The cohort members included all individuals who had an International Classification of Diseases, Ninth edition, Clinical Modification (ICD-9-CM) code 800-995 (excluding late effects from injury 905-909, and allergies from within 995), in the first or second diagnostic fields. …

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