Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “geographic variation”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources
PubMed1994

Why does geographic variation in health care practices matter? (And seven questions to ask in evaluating studies on geographic variation).

One of the most active fields in health services research is the study of "geographic variation," or disparities in rates of certain types of health care practices among large areas (such as countries or regions of a country) or small areas (such as countries or hospital market areas); "small area analysis" in particular has received much attention in journals and the popular press. Increasingly, data upon which to base studies of geographic variation are becoming available. This article poses questions to ask in applying studies on geographic variation to health care settings. Because findings from these studies may ultimately affect patient care, the questions are important for physicians as well as health services researchers. The questions are: 1) What events are to be analyzed? 2) What geographic units are to be analyzed? 3) How good are the data? 4) Are differences in rates due to chance alone? 5) Are high rates too high? 6) How is geographic variation to be explained? 7) What is the role of "presentation style" in explaining geographic variation?

Geography↗
PubMed1997

Geographic variation in stroke mortality in blacks and whites in the United States.

BACKGROUND AND PURPOSE: We sought to determine whether the "Stroke Belt" has continued to shift and to assess variation in geographic patterns by age, sex, and race. METHODS: Mortality data for Health Service Areas for 1988 to 1992 were used for analyses of geographic mortality patterns for stroke by race, sex, and age (50, 70, and 90 years). RESULTS: In 1988 to 1992, considerable geographic variation in stroke mortality was demonstrated for each sex/race group. In black and white women and men, previously described high mortality in the southeastern United States persisted. Mortality rates were generally higher in the South than in the North and in the East than in the West. Compared with data from 1962 to 1988, there was a continuation of the previously described westward shift of high-rate areas to the Mississippi River valley, a trend more marked at age 50 years than at 70 or 90 years. Although rates in the Pacific region were low overall, a surprising area of high rates was seen in southern California among women at all three ages examined. CONCLUSIONS: In whites, rapid declines in stroke mortality in the Southeast have left West South Central states with relatively high mortality rates; this trend may continue as younger cohorts age. However, rates in the Southeast also remain high, especially for blacks.

Black or African American↗
PubMed2001

Mitochondrial DNA variation and GIS analysis confirm a secondary origin of geographical variation in the bushcricket Ephippiger ephippiger (Orthoptera: Tettigonioidea), and resurrect two subspecies.

Geographic variation within species can originate through selection and drift in situ (primary variation) or from vicariant episodes (secondary variation). Most patterns of subspecific variation within European flora and fauna are thought to have secondary origins, reflecting isolation in refugia during Quaternary ice ages. The bushcricket Ephippiger ephippiger has an unusual pattern of geographical variability in morphology, behaviour and allozymes in southern France, which has been interpreted as reflecting recent primary origins rather than historical isolation. Re-analysis of this variation using Geographical Information Systems (GIS) suggests a possible zone of hybridization within a complex pattern of geographical variation. Here we produce a genetic distance matrix from restriction fragment length polymorphism (RFLP) bandsharing of an approximately 4.5 kb fragment of mitochondrial DNA (mtDNA), and compare this with predictions resulting from the GIS analysis. The mtDNA variation supports a postglacial origin of geographical variation. Partial Mantel test comparisons of genetic distances with matrices of geographical distance, relevant environmental characteristics and possible refugia show refugia to be the best predictors of genetic distance. There is no evidence to support isolation by distance. However, environmental contrasts do explain significant variation in genetic distance after allowing for the effect of refugial origin. Also, a neighbour-joining tree has a major division separating eastern and western forms. We conclude that the major source of variation within the species is historical isolation in glacial refugia, but that dispersal, hybridization and selection associated with environmental features has influenced patterns of mtDNA introgression. At least two valid subspecies can be defined.

Animals↗
PubMed1996

Geographical variations in rates of ophthalmic surgery.

AIMS/BACKGROUND: Geographical variations in health care are common. There is, however, no simple explanation for why they arise. Variations in rates of ophthalmic surgery in the population aged 65 and over were investigated, with the aim of determining their cause. METHODS: Routine data sources were used to obtain the 1991-2 age and sex standardised rates for English health districts with an ophthalmic unit. Weighted least squares regression was used to study the relation between these rates and various factors describing the population and the provision of care. RESULTS: Surgery rates varied more than threefold. High rates of surgery were associated with high throughput and bed numbers (both p < 0.001), high proportions of day case surgery (p < 0.001), long waiting lists (p < 0.001), and a high number of theatre sessions (p = 0.002). Conversely, a high percentage of emergency admissions was associated with lower rates of surgery (p = 0.004). These six variables accounted for 58% of the variation. CONCLUSION: Geographical variations were found to exist, less than two thirds being explained by differences in the provision of care. The remaining variation may partly be attributed to private practice and the lack of consensus for many ophthalmic procedures (the 'surgical signature'), including a lowering of the threshold for surgery. These findings have implications for the planning of ophthalmic services.

Aged↗
PubMed1999

Geographic variations in utilization rates in Veterans Affairs hospitals and clinics.

BACKGROUND: In the United States, geographic variation in hospital use is common. It is uncertain whether there are similar geographic variations in the health care system of the Department of Veterans Affairs (VA), which differs from the private sector because it predominantly serves men with annual incomes below $20,000, has a central system of administration, and uses salaried physicians. Thus, it might be less likely to have geographic variations. METHODS: We used VA data bases to obtain information on patients treated for eight diseases (chronic obstructive pulmonary disease, pneumonia, congestive heart failure, angina, diabetes, chronic renal failure, bipolar disorder, and major depression). We analyzed their use of hospital and outpatient services by assessing the risk-adjusted numbers of hospital days (the average number of days a patient spent in the hospital per 12 months of follow-up, regardless of the number of hospital stays), hospital-discharge rates, and clinic-visit rates from 1991 through 1995 for the entire system and within the 22 geographically based health care networks. RESULTS: We found substantial geographic variation in hospital use for all eight cohorts of patients and all the years studied. Variations in the numbers of hospital days per person-year among the networks were greatest among patients with chronic obstructive pulmonary disease (ranging from a factor of 2.7 to a factor of 3.1) during a given year and smallest among patients with angina (ranging from a factor of 1.5 to a factor of 2.1). Levels of hospital use were highest in the Northeast and lowest in the West. The variation in the rates of clinic visits for principal medical care among the networks ranged from a factor of approximately 1.6 to a factor of 4.0; variations in the rates were greatest among patients with chronic renal failure and smallest among patients with chronic obstructive pulmonary disease. There was no clear geographic pattern in the rates of outpatient-clinic use. CONCLUSIONS: There are significant geographic variations in the use of hospital and outpatient services in the VA health care system. Because VA physicians are unable to increase their income by changing their patterns of practice, our findings suggest that their practice styles are similar to those of other physicians in their geographic regions.

Chronic Disease↗
PubMed2001

Extent and sources of geographic variation in Medicare end-stage renal disease expenditures.

Geographic variations in practices and expenditures have been widely documented, leading to concerns that care in some regions is clinically suboptimal and/or economically inefficient. Our objectives are to determine the extent and sources of geographic variation in Medicare expenditures per patient with end-stage renal disease (ESRD) per year. The study population included all patients with ESRD with Medicare as primary payer during 1997 (n = 284,670). Medicare expenditures were summarized at the hospital referral region (HRR) level. Using regression analysis, we estimated the relationship between expenditures and demographics, case mix, dialysis provider characteristics, distribution of patients across renal replacement therapy modalities, standardized hospitalization ratios, and healthcare wages. Spending per patient-year varied threefold across HRRs, ranging from $17,791 to $59,025 (mean, $38,966 +/- $6,774 [SD]). The regression equation explained 80% of this variation. Although several demographic and case-mix indicators that have been related to spending at the individual level were statistically significant predictors of spending at the HRR level, they did not show enough geographic variation to explain a large fraction of spending variation. Rather, patient distributions across renal replacement modalities, hospitalization patterns, and healthcare wages were the most powerful predictors of spending. Compared with Medicare generally, both the mean and SD of ESRD expenditures were approximately seven times larger. The substantial geographic variability in expenditures for patients with ESRD indicates the potential for improving efficiency and quality of care. Interventions designed to increase transplantation rates, ensure access to peritoneal dialysis, and reduce hospitalization appear most promising.

Demography↗
PubMed1993

Explaining geographic variations. The enthusiasm hypothesis.

The causes of geographic variations in the use of health care services continue to puzzle researchers. Some have proposed that physicians in geographic areas with high rates of use provide proportionally more unnecessary care than those in other areas. Available research does not support this hypothesis. Others contend that uncertainty about the effectiveness of health services leads physicians to differing conclusions about when to perform various services and is the primary cause of geographic variations. Available research also does not support this hypothesis. This article proposes a different explanation, i.e., the enthusiasm hypothesis. Currently, research data suggest that geographic differences in the use of health care services are caused by differences in the prevalence of physicians who are enthusiasts for particular services. This analysis explores the validity of the enthusiasm hypothesis using previously published data on carotid endarterectomy.

Attitude of Health Personnel↗
PubMed1990

Geographic variation in sudden coronary death.

To describe geographic variations in an indicator of sudden coronary death, data from the National Center for Health Statistics were examined for deaths occurring out of hospital or in emergency rooms in 1984 to 1986 in 42 states. In white males aged 55 to 64 years, the percent of ischemic heart disease deaths coded as occurring out of hospital or in the ER ranged from 49.6% to 70.4%. The percents tended to be higher in mountain states and around Lake Michigan. However, neighboring states sometimes had very different percents. Within regions, percents were higher in nonmetropolitan than in metropolitan areas. Standard mortality ratios for white males of all ages revealed that several states had relatively high rates of death out of hospital or in the ER. These included New York, Michigan, and Wisconsin. High rates of coronary death out of hospital or in the ER may be due to high overall coronary death rates, high percent of coronary deaths occurring out of hospital or in the ER, or both. Further studies are needed of geographic variation in sudden coronary death and cardiac arrest and factors that might explain the variation such as emergency medical services. Place of death data from death certificates may be useful in monitoring efforts to prevent sudden coronary death.

Coronary Disease↗
PubMed1996

Lack of geographic variation in anonymous nuclear polymorphisms in the American oyster, Crassostrea virginica.

Comparing geographic variation of noncoding nuclear DNA polymorphisms, which presumably are neutral to natural selection, with geographic variation of allozymes is potentially a good way to detect the effects of selection on allozyme polymorphisms. A previous study of four anonymous nuclear markers in the American oyster, Crassostrea virginica, found dramatic differences in allele frequency between the Gulf of Mexico and the Atlantic Ocean. In contrast, 14 allozyme polymorphisms were fairly uniform in frequency between the two areas. This led to the conclusion that all of the allozyme polymorphisms were kept uniform in frequency by balancing selection. To test the robustness of this pattern, six additional anonymous nuclear DNA polymorphisms were surveyed in oysters from Panacea, Fla, and Charleston, S.C. on the Gulf and Atlantic coasts, respectively. Unlike the previously studied DNA markers, the six DNA polymorphisms examined here show geographic variation that is not significantly greater than that of allozymes. The reason for the discrepancy between the two sets of DNA polymorphisms is unclear.

Alleles↗
PubMed1999

Geographical variation in rate of schizophrenia in rural Ireland by place at birth vs place at onset.

This study examined geographical variation in rate of occurrence of schizophrenia by place at birth vs place at onset, among a rural Irish catchment area population of unusual stability and socioeconomic homogeneity. Within a catchment area of 21,520 persons, all cases of schizophrenia were sought using current inpatient and outpatient records and key informants active in the community. Suspected cases were interviewed personally and diagnosed using DSM-III-R criteria. Place at birth and place at onset of psychosis were specified among the 32 District Electoral Divisions constituting the study region. For the 72 cases ascertained, an unremarkable overall prevalence rate/morbid risk obscured substantial and significant geographical variations therein between District Electoral Divisions. Particularly after controlling for high-density families, men demonstrated prominent geographical variation both by place at birth and by place at onset, with most men remaining unmarried and becoming ill at their place of birth; conversely, women demonstrated prominent variation by place at birth but more limited variation by place at onset, despite more frequent transitions from the parental home to the marital home before onset. Even when cases changed their location before the onset of psychosis, geographical variation in rate of occurrence of schizophrenia remained associated more strongly with factors related to the place of their birth.

Adult↗
PubMed2001

Geographic variation in tool use on Neesia fruits in orangutans.

Geographic variation in the presence of skilled behavior may reflect geographic variation in genetic predispositions or ecological conditions (accompanied by reliable expression during development), or it may reflect the vagaries of invention and the appropriate social conditions for persistence. In this study, we compare the feeding techniques and tool-using skills used by orangutans to extract the nutritious seeds from Neesia fruits between Suaq Balimbing on Sumatra and Gunung Palung on Borneo, and map the distribution of Neesia tool use in Sumatran swamps. We show that neither genetics nor ecology is sufficient to explain the distribution of this tool use, confirming earlier findings on chimpanzees. We conclude that the ability to learn to use tools determines the geographic distribution. It is impossible to distinguish between the history of invention and the conditions for social transmission as the causal factors, but the high density and the social tolerance at Suaq Balimbing create propitious conditions for the maintenance of the skill as a tradition once it has been invented. High orangutan densities in the other Sumatran coastal swamps with Neesia tool use support the conclusion that suitable transmission conditions are the critical factor to explain the geographic distribution of skills such as feeding tool use.

Animals↗
PubMed1995

Temporal trends and geographical variations of peptic ulcer disease.

The present review describes the time trends and geographical variations of peptic ulcer disease. The study of the epidemiology of peptic ulcer is a worthwhile scientific endeavour, because it provides the necessary background against which hypotheses about the aetiology of the disease can be tested. For individual subjects, the risk of developing peptic ulcer depends upon their date of birth. The risk of developing peptic ulcer has risen in generations, i.e. birth-cohorts, born before the turn of the century, and declined in all subsequent generations. The birth-cohorts with the highest risk of developing gastric ulcer were born 10-20 years before those with the highest risk for duodenal ulcer. The birth-cohort pattern of peptic ulcer disease is found to be similar in all European countries, the USA, Australia and Japan. In gastric ulcer, the birth-related risk involves all ages over 5 years, while in duodenal ulcer it does not start before the age of 15 years. Gastric and duodenal ulcer are both characterized by marked geographical variations that are similar for both types. The similarity in geographical variation is shared by both sexes and all age groups older than 5 or 15 years in case of gastric and duodenal ulcer, respectively. The existence of a birth-cohort phenomenon implies that exogenous risk factors are responsible for the occurrence of peptic ulcer and that subjects are exposed to these risk factors during a limited period of their childhood or early adulthood. As the amount of exposure changes over time, consecutive generations come to reflect the varying amounts of exposure and risk for developing the disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Australia↗
PubMed1991

Evidence for geographical variations in the prevalence of schizophrenia in rural Ireland.

Geographical variations in the rate of occurrence of schizophrenia have been the subject of much speculation and controversy, but it has proved extremely difficult to establish the existence of the phenomenon within a given study area. Using current inpatient and outpatient records and information from key informants active in the community, this study sought to identify all cases of schizophrenia in 36 District Electoral Divisions, constituting a clinical catchment area of 25,178 persons in a rural Irish county. Though the overall prevalence rate (3.3 per 1000) was unremarkable, this obscured a substantial and significant variation in prevalence rates (from 0.0 to 14.3 per 1000) between District Electoral Divisions. Prevalence rates in five District Electoral Divisions made particular contributions to the overall deviation from a statistical model for random occurrences in space. The results indicate spatial inhomogeneity in the prevalence of schizophrenia in rural Ireland and imply geographical variation in environmental or genetic factor(s) of etiologic relevance.

Adolescent↗
PubMed1993

An assessment of radical prostatectomy. Time trends, geographic variation, and outcomes. The Prostate Patient Outcomes Research Team.

OBJECTIVES: To examine temporal trends and geographic variation in radical prostatectomy rates and short-term outcomes. DESIGN: Population-based study of radical prostatectomy for the years 1984 through 1990. Poisson regression was used to estimate temporal and regional effects. SETTING: The 50 states and the District of Columbia. PARTICIPANTS: A 20% national sample of male Medicare beneficiaries aged 65 years or older. MAIN OUTCOME MEASURES: Rate of radical prostatectomy; 30-day mortality; and major cardiopulmonary complications, vascular complications, or surgical repairs within 30 days of radical prostatectomy. RESULTS: A total of 10,598 radical prostatectomies were identified. The adjusted rate of radical prostatectomy in 1990 was 5.75 times that in 1984. The relative increase was similar in all age groups. Substantial geographic variation existed in rates from 1988 through 1990: all states in the New England and Mid-Atlantic regions had rates equal to or below 60 per 100,000 male Medicare beneficiaries, while all states in the Pacific and Mountain regions had rates equal to or above 130 per 100,000. The mortality and morbidity after radical prostatectomy are not trivial for older men (aged 75 years and older)--almost 2% died and nearly 8% suffered major cardiopulmonary complications within 30 days of the operation. CONCLUSION: The sharp increase and wide geographic variation in radical prostatectomy rates make the evaluation of this surgical procedure a pressing issue. The rising rate of radical prostatectomy among men aged 75 years and older merits special attention.

Aged↗
PubMed2001

Geographical variation in prevalence of hypertension within The Gambia.

Hypertension has become an important public health problem for sub-Sahara Africa. In a previous nationwide study, we observed a high degree of geographical variation in the prevalence of diastolic hypertension. Geographical variation provides essential background information for the development of community randomised trials could suggest aetiological mechanisms, inform control strategies and prompt further research questions. We designed a follow-up study from the nine high-prevalence communities, and from 18 communities where hypertension was found least prevalent (controls). In each community, 50 households were randomly selected. In each household, an (unrelated) man and woman were enrolled. The risk for hypertension (blood pressure > or =160/95 mm Hg) was higher in the high prevalence communities compared to the control villages (adjusted OR = 1.7, 95% CI 1.3-2.2). The observed coefficient of variation in hypertension prevalence, k, was 0.30. Thus we confirmed significant geographical variation in prevalence of hypertension over time, which has implications for planning of interventions.

Adolescent↗
PubMed2001

Variation in clinical decision making is a partial explanation for geographical variation in lower extremity amputation rates.

BACKGROUND: Rates of lower extremity amputation vary significantly both between and within countries. The variation does not appear to support differences in need as an explanation. This study set out to see if variations in clinical decision making might contribute to the explanation. METHODS: Based on an extensive audit database of lower extremity amputations and revascularization operations, a decision model was produced. Drawing on items in this model allowed the selection of six clinical cases that differed in their probability of having amputation as the outcome. Two cases had 80 per cent or more, two cases had 45--55 per cent and two cases had 20 per cent or less probability of amputation. Each of ten consultant vascular surgeons looked at these cases without knowledge of their probability of outcome and decided on amputation or revascularization. RESULTS: Overall the chance-adjusted level of agreement (kappa coefficient) between the decisions made by ten surgeons on the six clinical cases and the actual outcome was 0.46, indicating a moderate level of agreement. The kappa coefficient for individual surgeons showed complete agreement (kappa = 1) for four, substantial agreement (kappa = 0.66) for four, fair agreement (kappa = 0.32) for one and no agreement other than at a chance level (kappa = 0) for one surgeon. CONCLUSION: Variations in the clinical decisions made by vascular surgeons given the same patient are likely to explain at least a part of the observed geographical variation in rates of lower extremity amputation. Consensus guidelines may enable more consistent decision making for this problem.

Aged↗
PubMed1992

Empirical Bayes versus fully Bayesian analysis of geographical variation in disease risk.

This paper reviews methods for mapping geographical variation in disease incidence and mortality. Recent results in Bayesian hierarchical modelling of relative risk are discussed. Two approaches to relative risk estimation, along with the related computational procedures, are described and compared. The first is an empirical Bayes approach that uses a technique of penalized log-likelihood maximization; the second approach is fully Bayesian, and uses an innovative stochastic simulation technique called the Gibbs sampler. We chose to map geographical variation in breast cancer and Hodgkin's disease mortality as observed in all the health care districts of Sardinia, to illustrate relevant problems, methods and techniques.

Bayes Theorem↗
PubMed1985

Geographical variations in use of surgery for glue ear.

Study of geographical variations in the rate of surgery for glue ear reveals striking differences both between English health regions and between health districts. There are two-fold differences between regions and up to seven-fold differences between districts. Analysis of these differences at different levels of population aggregation reveals that professional uncertainty about the indications and value of surgery for this condition is the major factor responsible. In addition, the availability of otolaryngologists influences the surgical rate at district though not at regional level. The method used in this study is unable to determine the part played by geographical variation in patient expectation and morbidity rate. In contrast to the lack of consensus among otolaryngologists regarding the use of surgery for glue ear, there appears to be a high degree of agreement as regards tonsillectomy. The latter has coincided with the end of the decline in the tonsillectomy rate in the late 1970s.

Age Factors↗