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Figure 1 shows values for life expectancy. In the composite group the overall mortality ratio was 1.93 (1.17 to 3.13). We could not therefore distinguish mortality in these patients from that in the general population. In osteogenesis imperfecta type IA the overall mortality ratio was 1.08 (95% confidence interval 0.64 to 1.81). 4 Life expectancy figures were determined by applying the mortality ratios to the life tables for each age group. For each age, sex, or type group we recorded the observed mortality and compared it with that expected from the life tables for 1981. We carried out separate analyses of type IA, type III, and a composite group of moderate severity (types IB, IVA, and IVB). The total number of patient years was 6970 there were 57 deaths. The date of exit was 1 January 1993 or the date of death, if earlier. For each the date of entry was the date of ascertainment those notified before 1 January 1980 were given that date of entry. In all, 743 patients (383 type IA, 77 type IB, 123 type III, 90 type IVA, and 70 type IVB) were included.
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Patients whose survival to 1 January 1993 was uncertain or whose date of death was unknown were excluded. Patients identified only after death were excluded. Patients were excluded if they could not, with confidence, be assigned to one of the Sillence types, 3 or if they had the perinatal lethal form (type II). We limited our survey to patients in England and Wales. We sought to obtain reliable figures for life expectancy from our large survey of patients with osteogenesis imperfecta. In a recent review this is described as a severe disease in which “some patients reach adulthood.” 1 We were stimulated by requests for information for a patient told by an insurer that compensation would be reduced because of “poor life expectancy,” and for an affected child who wished to claim from her father's estate. No information is available on life expectancy in osteogenesis imperfecta it is often assumed that this is impaired. c Department of Management Science, University of Strathclyde, Glasgow G1 1XH.b Department of Epidemiology and Public Health, Ninewells Hospital and Medical School, Dundee DD1 9SY.a Department of Biochemical Medicine, Ninewells Hospital and Medical School, Dundee DD1 9SY.
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Rosalind M Henry, postgraduate student c.Simon A Ogston, lecturer in medical statistics b,.