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We outline the implementation of a new method of measuring the quality of medical care that counts cases of unnecessary disease and disability and unnecessary untimely deaths. First of all, conditions are listed in which the occurrence of a single case of disease or disability or a single untimely death would justify asking, "Why did it happen?" Secondly, we have selected conditions in which critical increases in rates of disease, disability, or untimely death could serve as indexes of the quality of care. Finally, broad categories of illness are noted in which redefinition and intensive study might reveal characteristics that could serve as indexes of health. We describe how these inth of the general population and the effects of economic, political, and other environmental factors upon it, and to evaluate the quality of medical care provided both within and without the hospital to maintain health and to prevent and treat disease.

Abstract. We prove that for any amenable non-singular countable equivalence relation R <= X x X, there exists a non-singular transformation T of X such that, up to a null set:R={(x, T n x);xeX, neZ}.It follows that any two Cartan subalgebras of a hyperfinite factor are conjugate by an automorphism. Statement of the resultsThe main result of this paper is that, for any amenable non-singular (n.s.) countable equivalence relation R <= X x X, there exists a non-singular transformation T of X such that, up to a null set, •-» (y, z)eR y . If R is given by the (not necessarily free) action of an amenable group, then it is straightforward to see that it is amenable. However, the equivalence relation of a non-singular action of a discrete group F can be amenable even though the group is not amenable. For instance, R. Zimmer [32] showed that, if F is a discrete subgroup of a Lie group, then the action of F on G/P where P is solvable, is amenable. In particular, F acting on the Furstenberg boundary B(G) is amenable. As a rule it is easier to check the amenability of an equivalence relation than to generate it by a single transformation. For instance, let F<=SL(2, R) be discrete. Then it will act amenably on Pi(R). However, to generate the corresponding equivalence relation by a single transformation is delicate even in the simplest case when F = SL (2, Z).Putting together the main result of our paper and the classification of W. Krieger [18] of a non-singular transformation up to weak equivalence, we obtain that the 432 A. Connes, J. Feldman and B. Weiss amenable countable equivalence relations are classified by non-singular flows. The amenability of a countable non-singular equivalence relation follows directly from the amenability of the associated von Neumann algebra (via the so-called 'group measure space construction').This, together with the above-mentioned result, shows that a given amenable von Neumann algebra M arises from at most one countable n.s. equivalence relation, which implies the uniqueness, up to an automorphism of M, of a Cartan subalgebra of M. In the case II X , a Cartan subalgebra is simply a maximal abelian subalgebra si of M whose normalizer generates M (as a von Neumann algebra). In the general case one has to assume further that si is discretely imbedded in M, i.e. that it is contained in the centralizer of a normal state (or equivalently is the range of a normal conditional expectation). BackgroundSince the papers of E. Hopf [15] and the first paper 'On rings of operators ' [21] of Murray and von Neumann, and their construction of factors from non-singular actions of discrete groups on Lebesgue measure spaces, there has been a fruitful interplay between the theory of von Neumann algebras and that part of ergodic theory dealing with orbit equivalence.In [22] Murray and von Neumann showed uniqueness, up to isomorphism, of factors of type Hi which are well approximated by finite dimensional subalgebras; they called this factor 'approximately finite'. Since factors of type Hi were also called fini...

Results indicate that an additional $4.6 billion will be spent over the lifetime of persons who acquired their impairment in 1998. The particularly high costs associated with prelingual onset of severe to profound hearing impairment suggest interventions aimed at children, such as early identification and/or aggressive medical intervention, may have a substantial payback.

The authors examined national changes in socioeconomic differentials in mortality for middle-aged and older white men and women in the United States with the use of 1960 data from the Matched Records Study and 1971-1984 data from the first National Health and Nutrition Examination Survey (NHANES I) Epidemiologic Follow-up Study (NHEFS). In 1960, there was little difference in mortality by educational level among middle-aged and older men. Since 1960, death rates among men declined more rapidly for the more educated than the less educated, which resulted in substantial educational differentials in mortality in 1971-1984. In contrast, among women, death rates declined at about the same rate regardless of educational attainment, so that a strong inverse relation between education and mortality in 1960 remained about the same magnitude during 1971-1984. Trends in educational differentials for heart disease mortality are responsible for much of the change for all causes of death. Relative risk estimates based on the NHEFS indicate that after taking into account selected baseline risk factors the least educated are still at substantially elevated risk of death from heart disease, ranging from a relative risk of 1.38 for men aged 65-74 years at baseline to 2.27 for men aged 45-64 years. Reasons for the observed educational differentials and their changes over time are not easily explained and are likely to be multifactorial.