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LETTER |
Correspondence: Requests for reprints should be sent to Bjarne Jansson, DrMedSc, PhD, Department of Public Health Sciences, Division of Social Medicine, Norrbacka Bldg, Karolinska Institutet, S17176 Stockholm, Sweden.
When assigning priorities, it is important to have correct information on the scope and magnitude of a health problem. In the March issue of the Journal, Kannus et al.1 reported an increasing trend in fall-induced injury deaths among the elderly. This is a well-known problem in most industrialized countries. The quality of cause-of-death statistics is regularly reviewed, but most studies compare death certificates with clinical records or autopsy reports. Only a few studies have focused on changes in registration practice, mainly the changeover from the eighth to the ninth revision of the International Classification of Diseases (ICD).2 Reporting errors due to coding errors at national statistics agencies are seldom considered, although a recent study by Graber et al.3 focused on national adaptations of coding instructions.
While epidemiologists are often aware of artifacts due to the implementation of a new version of the ICD, it seems to be less well known that important changes in coding practice may take place at other times. The selection of underlying cause of death is not always the result of strict application of ICD selection rules, but is often more a reflection of what coders feel is the most important condition to be reported on a certificate. Because of differences in the application of ICD selection rules, a condition that is selected as the underlying cause of death in one country might have been regarded as a contributory cause in another country. Therefore, both underlying and contributing causes of death should be analyzed.
When analyzing fall injury mortality, 2 diagnoses are important: pneumonia and fracture of the neck or other parts of the femur. Differences in proportions between underlying and contributing causes have been shown to be as much as 67% for pneumonia and 38% for femur fractures.4 Fife determined that among persons aged 75 years and older, injury deaths may be underestimated by as much as 50% overall.5 The problem occurs when a patient dies of multiple and late complications of an injury. This phenomenon, which has also been shown to occur with fall injuries due to epilepsy,6 will result in a serious underestimation of fall injury mortality. Another hidden problem not shown in national statistics is the concentration of fall injuries among patients with repetitive injuries due to a concentration of risk factors.7
In conclusion, both underlying and contributing cause-of-death statistics should be considered in any analysis of mortality trends. However, it is not always easy to assess the importance of registration practice in relation to other factors, such as changes in the natural history of diseases, altered diagnostic criteria and treatment methods, or even differences in reporting habits among physicians. These factors must be considered when comparing cause-of-death statistics from different countries.
References
1. Kannus P, Parkkari J, Niemi S, Palvanen M. Fall-induced deaths among elderly people. Am J Public Health.2005;95:422–424.
2. Smith GS, Langlois JA, Rocket IR. International comparisons of injury mortality: hypothesis generation, ecological studies and some data problems. Available at: http://www.cdc.gov/nchs/data/ice/ice95v1/c13.pdf. Accessed May 26, 2005.
3. Graber JM, Corkum BE, Sonnenfeld N, Kuehnert PL. Underestimation of cardiovascular disease mortality among Maine American Indians: the role of procedural and data errors. Am J Public Health.2005;95:827–830.
4. Jansson B, Johansson LA, Rosén M, Svanström L. National adaptations of the ICD rules for classification—a problem in the evaluation of cause-of-death trends. J Clin Epidemiol.1997;50(4):367–375.[CrossRef][ISI][Medline]
5. Fife D. Injuries and deaths among elderly persons. Am J Epidemiol.1987;126:936–941.
6. Jansson B, Ahmed N. Epilepsy and injury mortality in Sweden—the importance of changes in coding practice. Seizure.2002;11:361–370.[CrossRef][ISI][Medline]
7. Jansson B, Stenbacka M, Leifman A, Romelsjö A. A small fraction of patients with repetitive injuries account for a large portion of medical costs. Eur J Public Health.2004;14:161–167.
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