Variations in 'avoidable' mortality: a reflection of variations in incidence?

Background Variations in 'avoidable' mortality may reflect variations in th e quality of care, but they may also be due to variations in incidence or s everity of diseases. We studied the association between regional variations in 'avoidable' mortality and variations in disease incidence. For a select ion of conditions we also analysed whether the proportion of in-hospital de aths can explain the regional variations in incidence-adjusted mortality. Methods Relative risks for mortality, incidence, incidence-adjusted mortali ty and in-hospital mortality (1984-1994) were calculated by log-linear regr ession. Linear regression was used to examine the relationship between mort ality and incidence on the one hand, and between incidence-adjusted mortali ty and in-hospital mortality on the other. Results Significant regional mortality variations were found for cervical c ancer, cancer of the testis, hypertensive and cerebrovascular disease, infl uenza/pneumonia, cholecystitis/lithiasis, perinatal causes and congenital c ardiovascular anomalies. Regional mortality differences in general were onl y partly accounted for by incidence variations. The only exception was cerv ical cancer, which no longer showed significant variations after adjustment for incidence. The contribution of in-hospital mortality variations to tot al cause-specific mortality variations varied between conditions: the highe st percentage of explained variance was found for mortality from CVA (60.1% ) and appendicitis (29.2%). Conclusions Incidence data are a worthy addition to studies on 'avoidable' mortality. It is to be expected that the incidence-adjusted mortality rates are more sensitive for quality-of-care variations than the 'crude' mortali ty variations. Nevertheless, further research at the individual level is ne eded to identify possible deficiencies in health care delivery.