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Epidemiologic Methods↗
Biomedical subjects
S McLafferty
Publications and source records attributed to S McLafferty.
Breast cancer in West Islip, NY: a spatial clustering analysis with covariates.
This paper presents the results of an exploratory spatial analysis of breast cancer clustering in the community of West Islip on Long Island. Using address-level data from a survey of women in West Islip, we analyze the existence and locations of breast cancer clusters among long-term community residents. Statistical and geographical methods are used to first, estimate a logistic regression model of disease as a function of known risk factors and second, analyze spatial clustering among the cases of breast cancer not explained by the modeled risk factors. The method determines the actual locations of clusters so that if there is a potential causal factor in the environment it can be identified for further study. Although little evidence of clustering is uncovered, the methods described here have utility for exploratory spatial analysis in many health contexts.
Adult↗
Patient outcomes and regional planning of coronary care services: a location-allocation approach.
We explore the use of patient outcome criteria in planning the locations of critical care health services. Two attributes of the regional distribution of health services which influence health outcomes are: (1) the geographical accessibility of services and (2) the number of patients served by each facility (the patient volume). A model incorporating both factors is developed to determine the number, sizes, and locations of coronary care services in a region in order to maximize patient outcomes. We examine the implications and use of the model in an investigation of the location of coronary care units in rural upstate New York. The results indicate that a system consisting of fewer, well-located coronary care units would be superior for patient survival than the existing system of many dispersed units. Disparities in access to services between urban and rural areas are discussed.
Catchment Area, Health↗
Predicting the effect of hospital closure on hospital utilization patterns.
Geographic patterns of hospital utilization were analyzed before and after the closure of Sydenham hospital in New York City. The purpose was to determine the accuracy with which hospital utilization patterns after closure could be predicted using standard spatial interaction modeling procedures. Gravity models were calibrated to represent travel to hospitals before and after closure for patients residing in Sydenham's primary service area. Using three variables, hospital size, distance and type, the models accurately described utilization patterns in each year. The distance parameter, however, changed substantially between the 2 years. In addition large errors were observed when the model calibrated before closure was used to predict utilization patterns afterward. The geographic distribution and likely causes of errors were analyzed, along with their implications for spatial modeling efforts.
Catchment Area, Health↗
Cholinergic receptor mutants of the nematode Caenorhabditis elegans.
Potential acetylcholine receptor (AChR) mutants of the nematode are selectable by resistance to the neurotoxic drug levamisole, a probable cholinergic agonist. To determine which mutants may have achieved resistance through loss of levamisole receptor function, we have assayed mutant extracts for specific 3H-meta-aminolevamisole binding activity in the presence and absence of mecamylamine. We find that mutants in 3 of the 7 genes associated with extreme levamisole resistance are obviously deficient in saturable specific 3H-meta-aminolevamisole binding activity. Mutants of the 4 other genes have abnormal binding activities that fail to undergo the apparent allosteric activation of saturable specific 3H-meta-aminolevamisole binding activity caused by mecamylamine. Thus, all 7 genes appear to be required to produce a fully functional levamisole receptor. Mutants of several other genes associated only with partial resistance to levamisole have at least grossly normal receptor binding activities.
Animals↗
The levamisole receptor, a cholinergic receptor of the nematode Caenorhabditis elegans.
We describe a glass fiber filter binding assay for the levamisole receptor, a putative acetylcholine receptor of the nematode Caenorhabditis elegans, and we show that receptor detected in vitro binds both levamisole derivatives and cholinergic agonists with the pharmacological specificity expected of the physiologically functional nematode receptor. The receptor is detected by the binding of tritiated meta-aminolevamisole ([3H]MAL, 27 Ci/mmol). In extracts of the wild-type nematode, there is a saturable, high affinity binding activity for [3H]MAL (Kd approximately 5-10 nM). Well fed wild-type worms contain as much as 3 fmol of high affinity binding activity per mg of extract protein (0.14 pmol/g of wet weight of worms) and dauer larvae, a special juvenile stage, contain as much as 15 fmol of activity per mg of protein. Specific binding activity per mg of protein is highest in larval stages and decreases severalfold in the adult worm. The rates of formation and dissociation of the [3H]MAL-receptor complex are relatively slow (dissociation half-life, 17 min), in agreement with physiological studies of levamisole on Ascaris muscle strips. Levamisole derivatives and cholinergic agonists have the same relative potencies in inhibiting [3H]MAL binding as they do in causing nematode muscle contraction. Vertebrate cholinergic antagonists do not inhibit [3H]MAL binding, but several antagonists (mecamylamine, alpha-bungarotoxin, and cobra venom) potentiate the binding of [3H]MAL and can be used to demonstrate more clearly the presence of a second, lower affinity binding activity whose ligand-binding affinity is also potentiated by these agents. Both high and low affinity wild-type binding components are missing in the extremely levamisole-resistant mutant unc-74(x19).
Age Factors↗
The geographical restructuring of urban hospitals: spatial dimensions of corporate strategy.
In response to demographic, economic and regulatory change, hospitals in the United States are increasingly adopting the diverse corporate strategies of private firms. The ability of a hospital to adopt these strategies and survive depends greatly on the nature of the hospital institution and the economic potential of its geographical market area. A typology is developed relating institutional strategies such as merger, expansion, diversification and closure to the size of the hospital and the socio-economic status of the neighborhood in which it is located. Data describing the geographical distribution, since 1967, of hospital closures, mergers and facility expansions in New York City are used to examine institutional strategies in relation to the typology. Closure has been most common among small hospitals located in low SES neighborhoods, whereas facility expansion has been most prevalent among large hospitals located in high status neighborhoods. The result is an increased concentration of patient care in large tertiary hospitals. Mergers have provided a means of not only increasing institutional size and rationalizing services, but also of establishing footholds in 'profitable' marked areas. The final section considers the role of the state in hospital restructuring.
Economic Competition↗
Neighborhood characteristics and hospital closures. A comparison of the public private and voluntary hospital systems.
This paper analyzes the neighborhood distribution of hospital closures in New York City between 1970 and 1981. Discriminant analysis procedures are used to compare the social, economic and health status characteristics of neighborhoods in which hospitals have closed with those of neighborhoods in which facilities have remained open. The results show that overall hospital closures have had a substantial distributional impact, with facilities in low-income, high infant mortality neighborhoods having the highest rates of failure. Closures of voluntary hospitals occurred most frequently in disadvantaged neighborhoods; whereas municipal and proprietary hospital closures showed no differential neighborhood impact. Implications for the geographical accessibility to various groups to health care and for the efficiency and cost of hospital services are discussed.
Catchment Area, Health↗