Variations in hospitalization rates among nursing home residents: the role of discretionary hospitalizations - Methods - Illustration

Health Services Research, August, 2003 by Mary W. Carter

Findings from the larger body of geographic variations research exploring hospital use rates among community-based populations offers insight regarding methods that are likely to be useful in exploring variations in hospitalization rates among nursing home based populations. For example, previous studies have established that community hospital discharge rates for certain low discretionary conditions (e.g., myocardial infarction) exhibit much less dispersion among geographic regions relative to discharge rates for more highly discretionary conditions (e.g., transient cerebrovascular ischemia) (Paul-Shaheen, Clark, and Williams 1987)--where discretionary refers to the degree to which doctors face uncertainty regarding the use of in-hospital treatment versus other treatment options. While there is no consensus, many researchers believe that when clear and compelling medical guidelines are absent, decisions to hospitalize may be influenced by the availability of area resources, leading to what has been called, "supply-sensitive" hospitalizations (Wennberg 2002). Moreover, the extent to which supply-sensitive differences are observed through variations in hospitalization rates appears to vary with the level of professional discretion associated with a particular condition (Fisher et al. 2000; Roos, Wennberg, and McPherson 1988). Thus, it follows that hospitalizations among nursing home residents that can be classified as highly discretionary should also exhibit greater variability compared to less discretionary hospitalizations. In response, this paper posits that the extent to which highly discretionary conditions are more sensitive to contextual and supply-sensitive factors will be reflected in the role of facility-level organizational and structural factors and area-market health delivery factors in explaining variations of nursing home hospitalization rates, after controlling for differences in population case-mix. Since ideally, hospital transfers should be relatively invariant to contextual and market-level attributes, consideration of the discretionary level provides some optimism for expanding our understanding of the contribution of nonclinical factors to variations in hospital use among nursing home residents.

PREVIOUS RESEARCH

Community-based utilization studies have repeatedly shown that hospitalization rates vary widely across small geographic areas (Paul-Shaheen, Clark, and Willams 1987). Although some variation might be expected to occur due to demographic diversity across regions, attempts to adjust for differences in population case-mix have failed to attenuate wide disparities in hospitalization rates across even the most similar geographic areas of study (Wennberg and Gittelsohn 1982). Moreover, the disparity in hospitalization rates across geographic areas has persisted despite extensive changes to health care policy, including implementation of the Medicare and Medicaid programs (Fisher et al. 2000). The failure of factors such as population morbidity levels and insurance coverage rates to account for variations in hospitalization rates across neighboring regional areas underscores the likelihood that the observed disparity in hospital use reflects not only overusage, but underusage as well. Overusage implies unnecessary and costly use of scarce resources, while underusage implies insufficient health care provision to the medically needy.

Given the inability of factors such as differential morbidity and access levels across populations to explain small area variations in hospitalization rates, researchers Wennberg, Barnes, and Zubkoff (1982) advanced the professional uncertainty principle, which focuses on the contribution of the decisional component by physicians to hospital variation rates. The professional uncertainty principle holds that among physicians, a considerable level of professional discretion in deciding whether or not to hospitalize exists, due in part because at times medical conditions may lack widely established treatment protocols or clear and convincing evidence to support one treatment option over another. Thus, when the relative benefit of one procedure is not well known over another procedure, physicians may face considerable uncertainty regarding which course of action to follow. At times, therefore, when standard treatment protocols are not widely established or broadly followed by practitioners, professional judgment to hospitalize may be highly discretionary. Furthermore, when ambiguity regarding treatment for a given condition exists, physicians' decisions may be influenced by the availability of local resources and the tendency to act under the assumption that "more is better," leading to marked variations in hospitalization rates across relatively small and demographically similar regions (Wennberg 2002; Fisher et al. 2000; Wennberg, Barnes, and Zubkoff 1982).

Research findings provide empirical support for the notion of supply-sensitive services contributing to variations in hospital use. For instance, rates of tonsillectomies were shown to vary across six Vermont regions from a low of 8 percent to a high of 65 percent. Interestingly, when the physicians practicing in the area with the highest rate of tonsillectomy referrals were informed of their greater tendency to choose surgery over other treatment options, the rate of tonsillectomy referrals dropped rapidly and significantly. Similar findings for procedures such as hysterectomies, prostatectomies, and varicose veins have also been reported (Wennberg, Barnes, and Zubkoff 1982). More recently, Fisher and colleagues (1994) examined unexplained variations in readmission rates between Medicare beneficiaries residing in two neighboring communities: Boston, Massachusetts, and New Haven, Connecticut. Findings indicated that regardless of the medical condition responsible for the first hospitalization event, Medicare beneficiaries from Boston held odds 1.64 times greater of being rehospitalized than did their New Haven counterparts.