Variation In Mortality Research Articles

Variation in death rate after abdominal aortic aneurysmectomy in the United States: impact of hospital volume, gender, and age.

To determine whether high-volume hospitals (HVHs) have lower in-hospital death rates after abdominal aortic aneurysm (AAA) repair compared with low-volume hospitals (LVHs). Select statewide studies have shown that HVHs have superior outcomes compared with LVHs for AAA repair, but they may not be representative of the true volume-outcome relationship for the entire United States. Patients undergoing repair of intact or ruptured AAAs in the Nationwide Inpatient Sample (NIS) for 1996 and 1997 were included (n = 13,887) for study. The NIS represents a 20% stratified random sample representative of all U.S. hospitals. Unadjusted and case mix-adjusted analyses were performed. The overall death rate was 3.8% for intact AAA repair and 47% for ruptured AAA repair. For repair of intact AAAs, HVHs had a lower death rate than LVHs. The death rate after repair of ruptured AAA was also slightly lower at HVHs. In a multivariate analysis adjusting for case mix, having surgery at an LVH was associated with a 56% increased risk of in-hospital death. Other independent risk factors for in-hospital death included female gender, age older than 65 years, aneurysm rupture, urgent or emergent admission, and comorbid disease. This study from a representative national database documents that HVHs have a significantly lower death rate than LVHs for repair of both intact and ruptured AAA. These data support the regionalization of patients to HVHs for AAA repair.

Death rate variation in US subpopulations.

To account for variations in death rates in population subgroups of the USA. Factors associated with age-adjusted death rates in 366 metropolitan and non- metropolitan areas of the United States were examined for 1990-92. The rates ranged from 690 to 1108 per 100 000 population (mean = 885 +/- 78 per 100 000). Least squares regression analysis explained 71% of this variance. Factors with the strongest independent positive association were ethnicity (African-American), less than a high school education, high Medicare expenditures, and location in western or southern regions. Factors with the strongest independent negative associations were employment in agriculture and forestry, ethnicity (Hispanic) and per capita income. Additional research at the individual level is needed to determine if these associations are causal, since some of the factors with the strongest associations, such as education, have long latency periods.

Very-low-birth-weight infant outcomes in 11 South American NICUs.

To describe and analyze outcomes in very-low-birth-weight (VLBW) infants treated in 11 Neonatal Intensive Care Units (NICUs) from four South American countries. This study is the first of a multination collaboration and can serve as a baseline for future quality and resource utilization efforts. Biodemographic data and multiple outcome measures were prospectively collected from October 1997 until August 1998. A logistic regression model was used to define risk factors in primary outcome measures, death, and bronchopulmonary dysplasia (BPD). Center differences were compared using chi-squared analysis. In 385 VLBW infants enrolled, mortality rate was 27%, with a range from 11% to 51% among NICUs. A lower BW, lower gestational age (GA), lack of antenatal steroids (AS), and air leaks (AL) were associated with increased risk of death. A lower BW, lower GA, AL, need for surfactant, necrotizing enterocolitis, and need for intubation were associated with increased risk of BPD. This study provides actual information about VLBW infants' prognosis in a SA region. Mortality rate variability among NICUs may be explained by differences in population and resources, but also by lack of implementation of proven beneficial therapies such as AS administration.

Evaluating inter‐hospital variability in mortality rates over time, allowing for time‐varying effects

In outcome studies, quality of care in various institutions is typically assessed by comparing observed to expected outcome rates, after adjusting for patients' case-mix factors in logistic regression models. However, differences in patterns of outcome rates over time, especially when there is a distinction between the determinants affecting early and later events, are rarely studied. We use six-month mortality after coronary artery bypass graft operation (CABG) as an example. We present a statistically valid approach to estimate expected survival curves for different subgroups, based on a Cox survival model with time-varying effects. Bootstrap confidence intervals around the expected survival curves are constructed. This approach is applied for examining the pattern of deviation of high-mortality hospitals after CABG. Implications for quality assessment in comparative outcome studies are discussed.

Viability of the southern elephant seal population of the Falkland Islands

AbstractAccurate long‐term series of demographic data are available for most populations of southern elephant seals. However, research on the elephant seals of the Falkland Islands began only recently, and information for an accurate forecasting of the future of this population is lacking. In this paper we present data on the current status of the population and its trend in size during the last 11 years. We built an age‐structured model of the population and analyzed the effect of variation in demographic parameters on population growth. Elasticity analysis demonstrated that variation in mortality has a more pronounced effect on instantaneous growth rate than an equivalent variation in fecundity. We examined the effects of environmental variability, inbreeding and catastrophes on population viability by a computer simulation using the VORTEX PVA programme. In the stochastic model, the most important factor affecting extinction risk was variability in mortality rates, in particular of the adult classes. We concluded that, although the population does not appear to be at immediate risk of extinction, its small size and isolation make it necessary to accurately monitor the population trends and to acquire additional information on life history and feeding strategies.

Heterogeneity in Individual Mortality Risk and Its Importance for Evolutionary Studies of Senescence.

Mortality was simulated under the assumption of heterogeneity in individual age-specific mortality risk. Heterogeneity was modeled by assigning each individual its own Gompertz mortality function. Means and variances of the Gompertz intercept and slope parameters were based on published data for Drosophila melanogaster. Simulations of large cohorts reproduced mortality plateaus similar to those observed for actual cohorts of flies. Catastrophic late-age mortality was not observed except when heterogeneity was very low and rates of senescence were very high. A second set of simulations was designed to mimic experiments that have investigated age-specific patterns of genetic variance in mortality rates. Within-genotype heterogeneity in mortality risk resulted in a decline in genetic variance of mortality rates at old ages. That result suggests that the decline in genetic variance at old ages that has been observed in some experiments is an artifact of heterogeneity. Mortality rate plateaus, decrease in genetic variance of mortality rates at old ages, and absence of catastrophic late-age mortality all appear to contradict predictions of the evolutionary theory of senescence. Heterogeneity in mortality risk may explain those contradictions.

The Impact of COPD on Lung Health Worldwide: Epidemiology and Incidence

Information on the prevalence of COPD was obtained from vital statistics, health interview surveys, hospital charge records, national publications, and the World Health Organization (WHO). These data indicate that COPD is a common disease with implications for global health. In the United States, morbidity caused by COPD is 4%, making COPD the fourth leading cause of death, exceeded only by heart attacks, cancer, and stroke. Internationally, there is substantial variation in death rates possibly reflecting smoking behavior, type and processing of tobacco, pollution, climate, respiratory management, and genetic factors. The Global Obstructive Lung Disease Initiative, initiated by the National Heart, Lung, and Blood Institute and the WHO, aims to raise awareness of the increasing burden of COPD, decrease morbidity and mortality, promote further study of the condition, and implement programs to prevent COPD.

Women's heart problems are poorly understood.

Why and when women develop heart disease is both poorly understood and studied, said experts at the 21st Congress of the European Society of Cardiology, held in Barcelona. “Men and women are similar with regard to risk factors,” said John Martin, MD, of the University of London Cardiology Group. These similar heart disease risk factors include high blood pressure, high cholesterol, smoking, and age, said Dr Martin. Yet, he said, women with diabetes often have a higher risk of heart disease than men with diabetes. Women are also more likely to die of a first heart attack than men. As with men, death rates from heart disease in women vary from country to country. Heart disease death rates for women are lowest in Spain and highest in Scotland, he said. Again, as with men, this variation in rates is not well-understood. Even more puzzling are the variations in death rates, particularly in the acute phase just after a heart attack, when the patient is hospitalized. In a recent study in the New England Journal of …

Mortality in end-stage renal disease: a reassessment of differences between patients treated with hemodialysis and peritoneal dialysis.

Recent registry studies comparing mortality between peritoneal dialysis (PD) and hemodialysis (HD) patients show conflicting results. The purpose of this study is to determine whether previously published results showing higher mortality for patients treated with PD versus HD in the United States continue to hold true over the period 1987-1993. National mortality rates for PD and HD were extracted from the U.S. Renal Data System (USRDS) annual reports for the cohort periods: 1987-1989, 1988-1990, 1989-1991, 1990-1992, and 1991-1993. Using Poisson regression, death rates per 100 patient years were compared between PD and HD for each cohort period controlling for age, gender, race, and cause of end-stage renal disease (diabetes versus nondiabetes). When incident patients and patients with a prior transplant were included in the analysis, starting with the 1989-1991 cohort, we found little or no difference in the relative risk (RR PD:HD) of death between PD and HD (1987-1989: RR = 1.17, P < 0.001; 1988-1990: RR = 1.12, P < 0.001; 1989-1991: RR = 1.06, P = NS; 1990-1992: RR = 1.06, P = NS; 1991-1993: RR = 1.08, P = 0.043). After a test for goodness-of-fit, separate analyses for diabetic patients and nondiabetic patients were done to examine unexplained variation in death rates. For nondiabetic patients, there was less than a 1% difference in the adjusted 1-yr survival between PD and HD from 1989-1993 (1989-1991: RR = 1.05, P = NS; 1990-1992: RR = 1.04, P = NS; 1991-1993: RR = 1.07, P < 0.01). Among diabetic patients, the PD:HD death rate ratio varied significantly according to gender and age. For the average male diabetic patient, there was little or no difference in risk between PD and HD from 1989-1993 (1989-1991: RR = 1.02, P = NS; 1990-1992: RR = 1.05, P = NS; 1991-1993: RR = 1.08, P < 0.01). For diabetic patients under the age of 50, those treated with PD had a significantly lower risk of death than those treated with HD (1989-1993: 0.84 < or = RR < or = 0.89, P < 0.005). Over the same period, female diabetic patients treated with PD had a higher risk, on average, than HD (1.18 < or = RR < or = 1.19, P < 0.001) as did diabetic patients over the age 50 (1.28 < or = RR < or = 1.30, P < 0.001). Unlike previously published results that were restricted to prevalent-only patients, this national study of both prevalent and incident patients found little or no difference in overall mortality between PD and HD. The recent trends in mortality likely reflect the inclusion of incident patients, but they may also reflect changes in case-mix differences and/or improved PD practice. Additional incident-based studies that allow for additional case-mix adjustments are needed to better compare outcomes between HD and PD.

Multi‐level modelling of geographically aggregated health data: a case study on malignant melanoma mortality and UV exposure in the European Community

A multi-level modelling approach is used to examine the variance in mortality rates from malignant melanoma at different geographical scales within nine European nations with reference to exposure to ultraviolet light (UVB). For males and females, the greatest variations in the relationship between UVB exposure and mortality are seen between nations, rather than regions and sub-regions within nations. This suggests that factors and characteristics acting at a national scale, such as genetic and behavioural differences, are of importance. Multi-level modelling is used to show how a previous suggestion of a quadratic association between UVB exposure and malignant melanoma across Europe is unlikely to be true. The general usefulness of multi-level modelling in the analysis of disease data which is structured in a hierarchy is discussed, with particular reference to geographical analyses of small area data. © 1998 John Wiley & Sons, Ltd.

Multi-level modelling of geographically aggregated health data: a case study on malignant melanoma mortality and UV exposure in the European Community.

A multi-level modelling approach is used to examine the variance in mortality rates from malignant melanoma at different geographical scales within nine European nations with reference to exposure to ultraviolet light (UVB). For males and females, the greatest variations in the relationship between UVB exposure and mortality are seen between nations, rather than regions and sub-regions within nations. This suggests that factors and characteristics acting at a national scale, such as genetic and behavioural differences, are of importance. Multi-level modelling is used to show how a previous suggestion of a quadratic association between UVB exposure and malignant melanoma across Europe is unlikely to be true. The general usefulness of multi-level modelling in the analysis of disease data which is structured in a hierarchy is discussed, with particular reference to geographical analyses of small area data.

Using Admission Characteristics to Predict Short-term Mortality From Myocardial Infarction in Elderly Patients

To develop a prediction model of death within 30 days of hospital admission for Medicare patients with acute myocardial infarction that would permit use of risk-adjusted mortality rates as hospital quality measures. Retrospective cohort study using data created from medical charts and administrative files. All acute care hospitals in Alabama, Connecticut, Iowa, or Wisconsin. A cohort of 14,581 patients with acute myocardial infarction covered by Medicare in 1993. The unadjusted 30-day mortality rate was 21%, ranging from 18% in Connecticut to 23% in Alabama. The 4 largest contributors to variability in mortality rates were mean arterial pressure, age, respiratory rate, and serum urea nitrogen level. The area under the receiver operator characteristic curve was 0.79 in a developmental sample of 10 936 patients and 0.78 in a validation sample of 3645 patients. Based on admission variables, we were able to explain 27% of the variability in 30-day mortality rates. During the index admission, aspirin, beta-blockers, angiotensin-converting enzyme inhibitors, and thrombolytic agents were used in 72%, 39%, 32%, and 15% of patients, respectively. Explained variation increased by 6 percentage points to 33% when drug therapies and revascularization procedures performed during the index admission were added to the model predictors. Short-term mortality remains high for elderly patients with acute myocardial infarction, and a large percentage of variation remains unexplained after controlling for admission severity. Part of the unexplained variability can be explained by the location of the admitting hospital; some of the remaining unexplained variation may reflect differences in quality of care or unmeasured differences in disease severity. Researchers should develop quality indicators based on process measures for acute myocardial infarction and should incorporate these measures into mortality models to determine whether quality accounts for variation in 30-day mortality rates beyond that explained by clinical status at admission.

Geographic variation in vascular mortality in eurasia: Relationship between mortality variables and risk factors

This study was based on a sample of 68 populations from 42 countries of Eurasia. Most of the data were from the MONICA Project, while additional information was from the abundant literature. Mortality rates (from cardiovascular, cerebrovascular and ischaemic heart diseases, and death rate from all causes) and related to them potential risk factors (systolic and diastolic blood pressure, total serum cholesterol and body mass index) were described for men and women, separately for 5 age cohorts, ranging between 25 and 64 years. The results showed that, in contrast to the studies carried out on theintrapopulational level, in our work risk factors did not demonstrate any strong association with mortality rate variables. Moreover, it was found that the vascular mortality on theinterpopulational level explains between 57% and 71% in total mortality and could serve as a quite fair indicator of the populational well-being in general. Although mortality rate from vascular diseases in women was much lower than in man of equal ages, geographic variation of the above mentioned death rates has showed a very similar pattern in the two sexes: the death rate is high in women when it is high in men.

Components of small area variation in death rates: a method applied to data from Sweden.

The study aimed to develop and evaluate a method for small area analysis of different non-random components of the variation in death rates. The method was applied to incidence and mortality data for selected malignant neoplasms in 26 administrative health areas in Sweden. Variation in mortality and incidence rates for malignant neoplasms of the trachea, bronchus, and lung; colon; rectum; and cervix uteri in the 26 health areas were analysed after standardisation for age. In addition, the systematic and random components of variance were estimated. The systematic component of variance in mortality was divided into two additive components-one component was dependent on the variation in the corresponding incidence rates and the other remained after adjustment for incidence. SETTING AND PARTICIPANT: All cases diagnosed between 1972 and 1983 and all deaths between 1974 and 1985 for selected malignant neoplasms in Swedish citizens and other residents in Sweden, aged between 0 and 64 years, were analysed. Much of the observed variation in mortality was explained by the estimated random variation. For malignant neoplasms of the trachea, bronchus, and lung the systematic variation in mortality was mainly explained by the variation in incidence. For cancer of the cervix uteri, alone, there was significant systematic variation of moderate magnitude that was not explained by the incidence rates. These methods made it possible to divide the observed variance in mortality into different components. Random effects and variance in incidence rates were found to be of great importance when analysing the variance in death rates between health areas. By studying different systematic components of variation it is possible to identify fields for in depth studies on the quality of prevention and treatment.

Kinetics and Modeling of Lactic Acid Production by Lactobacillus plantarum

An unstructured model was developed to describe bacterial growth, substrate utilization, and lactic acid production by Lactobacillus plantarum in cucumber juice. Significant lactic acid production occurred during growth, as well as stationary phases. The percentage of acid produced after growth ceased was a function of the medium composition. Up to 51% of the lactic acid was produced after growth ceased when NaCl was not present in the medium, whereas not more than 18% of the total lactic acid was produced after the growth ceased in presence of NaCl, probably because of an increase in the cell death rate. An equation relating the specific death rate and NaCl concentration was developed. With the kinetic model proposed by R. Luedeking and E. L. Piret (J. Biochem. Microbiol. Technol. Eng. 1:393-412, 1958) for lactic acid production rate, the growth-associated and non-growth-associated coefficients were determined as 51.9 (+/-4.2) mmol/g of cells and 7.2 (+/-0.9) mmol/g of cells h respectively. The model was demonstrated for batch growth of L. plantarum in cucumber juice. Mathematical simulations were used to predict the influence of variations in death rate, proton concentration when growth ceased, and buffer capacity of the juice on the overall fermentation process.

The impact of HIV-1 infection on mortality in children under 5 years of age in sub-Saharan Africa

To estimate the effects of the HIV-1 epidemic on mortality in children under 5 years of age in urban and rural populations in eastern and central, and southern Africa. A lifetable method that allows for the effects of competing causes (i.e., mortality due to HIV and other causes) was used to estimate mortality. Our calculations used published and unpublished data on HIV-1 infection in African adults and children (incidence and prevalence, vertical transmissions, transmission by blood transfusion and natural history), and typical baseline fertility and child mortality data. The results were applied to model rural and urban populations to explore the effects of parameters such as mortality in HIV-1-infected children, fertility in infected mothers and overall population growth. We estimate that child mortality will rise substantially because of the prevalence of HIV-1 in urban areas. There will be little difference in the absolute levels of increase in mortality between areas in eastern and central, and southern Africa with similar levels of HIV infection; however, in relative terms the effect will be more noticeable in southern Africa because of the lower baseline mortality. Towns with severe epidemics (30% adult seroprevalence) might experience a rise in child mortality of one-third in eastern and central Africa and three-quarters in southern Africa. This will cancel or reverse existing advantages in urban over rural levels of child mortality and this effect will be more pronounced in southern Africa. The exact impact of HIV-1 will vary according to mortality among HIV-1-infected children and to fertility among infected women. However, changes in age structure and population growth have relatively little impact on mortality. There are likely to be substantial increases in child mortality in sub-Saharan Africa as a result of HIV-1 infection. The main determinant of childhood infection is the scale of the epidemic among adults. Increases in mortality will depend on local adult seroprevalence but are hard to predict precisely because of possible variation in death rates among HIV-1-infected children. In rural areas with low seroprevalence other diseases will remain the main cause of mortality. However, in urban areas families and health services will have to face considerably increased demands from ill and dying children.

Indicators of "avoidable" mortality in health administrative areas in Sweden 1974-1985.

When comparing health administrative areas in Sweden the variation in death rates for 13 suggested indicators of avoidable mortality was analysed for the time periods 1974-79 and 1980-85. For most indicators the variation was significant. The level of systematic (nonrandom) variance differed between the sexes for certain conditions. According to the theory of mass-significance it would be appropriate to use a sharpened significance test of high SMRs. For certain health policy indicators it was possible to detect areas accounting for nearly all the deviation above the national standard using a sharpened test (p < 0.001). For most medical care indicators, however, the high death rates had a lower level of significance. When sensitivity is given priority an ordinary test (p < 0.05) should be preferred. This means, however, dealing with potential false positive warning signals. Epidemiological surveillance of indicators of avoidable mortality should be the starting point for in-depth studies.

A critical analysis of the design, results and implications of the Mortality and Use of Health Services surveys.

This article is a discussion of the design and methods of program impact surveys conducted as part of the Combatting Childhood Communicable Diseases (CCCD) program. Independent reviews are given of the analysis of results from Liberia and Zaire. The CCCD evaluations aim to examine the performance of routine technologies in national programs rather than to test the efficacy of new technologies and demonstrate the impact on mortality and morbidity. The argument is presented that mortality and morbidity are insufficient indicators of improvements in quality of life of reductions in suffering or of short-term changes in health status. Short-term changes are best measured as mortality based on a full reporting of births and deaths as occurs in a vital registration system over a number of years. Retrospective surveys are considered to be flawed by systematic biases problems of omission and misdating of events. The widely used Brass method is viewed as not producing estimates for exact time periods and data from aged 15-29 years are affected by selection effects. Field conditions have an important effect on results. Sometimes the quality of field work is assessed on the basis of plausibility of results. Interseasonal and interannual variations in death rates can be substantial. Outcomes are unpredictable. Randomized control trials with or without controls for community level factors require large sample sizes but are argued by some researchers to be more successful. Cause specific changes in mortality offer a more useful measure of impact and increase the level of significance of the impact. Limitations are the interaction between causes of death and the unreliability in the identification of causes. Ideally evaluation should involve an estimation of longterm mortality trends documentation of mortality change pre/post-intervention a control group and data on causes of death targeted by the intervention. The surveys in Liberia and Zaire are noteworthy for attempting to rigorously measure program impact but the impact of service delivery and mortality is limited. Concern is raised that poor assessment measures will lead to poor future policy choices.

Reducing coronary heart disease in England: targets and implications

IN a previous paper we reported on the extent of district health authority (DHA) variability in mortal ity from coronary heart disease in England. In this paper we discuss two issues: possible methods for setting target levels of mortality for individual DHAs, and the implications of the variations for action by those involved in health education and health pro motion. We are not suggesting that targets should be 'top down', but that districts should be able to assess an appropriate contribution to a national target, tak ing account of local circumstances. In addition, local targets should not be an excuse for inaction at national level. A commitment is required, not least from central government, in pursuing progressive public health measures, including issues of food pol icy and strict price and advertising control of smok ing.

Environmental findings and sudden infant death syndrome

Sudden infant death syndrome (SIDS) death rates show substantial seasonal variation. Analysis of this variation shows that it is due to postnatal factors. Possible variables are temperature, infection, pollution, and the infants' interaction with the social environment. In England and Wales the temporal pattern of pollution levels and the geographical variation of death rates do not suggest pollution is generally an important factor. Social environment appears the most important. One in three high risk infants are in families with multiple social problems compared with 9% of controls. Further studies of why some infants are at greatly increased risk might identify crucial adverse environmental factors and indicate how some deaths could be prevented.