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PubMed1990

Can changes in the unemployment rates explain the recent changes in suicide rates in developed countries?

Data were collected on unemployment and suicide rates in 16 developed countries for 1973 and 1983 (suicide rates were three-year averages). Unemployment rates rose appreciably in men and women in all countries. Among men suicide rates rose in 14 of the countries whereas among women they did so in only seven. A mathematical model was developed to investigate, for those countries with increased suicide rates, how much of the increase could be contributed by an increase in the numbers unemployed. It was found that the proportion of the increase that could be 'explained' varied considerably between countries. In general the amount of the increase explained was small, and often a considerable increase in the suicide rates among those employed would be required to account for the observed increase in the suicide in the whole population. It is concluded that unemployment shows an inconsistent relationship with suicide. Further, if a relationship does exist in some countries the effect may be as much a generalized one on the whole population as a specific effect on the unemployed. Finally the possible effects of unemployment on suicide differ appreciably between men and women.

Adolescent↗

PubMed1995

Ways of seeing: explaining variations in use of acute hospital services.

BACKGROUND: In the US Medicare programme, hospitals are paid directly by activity. To provide incentives for efficiency, the US Federal Government has sought objective measures of inpatients' need for resources. In the UK National Health Service, resources are allocated for acute hospital services as part of a global budget to purchasers, who then contract with hospitals. To provide equity in resource allocation, the Department of Health in England, has sought objective measures of populations' need for resources. METHODS: Examination of policy and technology that has used variations in utilization of resources to derive objective measures of efficiency and equity. RESULTS: The technology of developing empirical measures of resources needed by patients has lacked information on outcomes, which is vital for measures of efficiency. The technology of developing empirical measures of resources needed by populations has relied on aggregate data. Analyses of specific procedures and conditions consistently find that these variations are explained by differences in medical practice and not by need. CONCLUSIONS: There is scope for multidisciplinary research to explain small area variations for specific procedures and conditions in resources used by populations. It seems unlikely, however, that governments will be interested in findings from this research.

Health Care Rationing↗

PubMed1996

Alcohol, fish, fibre and antioxidant vitamins intake do not explain population differences in coronary heart disease mortality.

BACKGROUND: Within the Seven Countries Study data we investigated whether population differences in 25-year mortality rates from coronary heart disease could be explained by population differences in alcohol, fish, fibre and antioxidant intake. METHODS: Baseline surveys were carried out between 1958 and 1964, on 12 763 middle-aged men constituting 16 cohorts in seven countries. In 1987 and 1988 equivalent food composites representing the average food intake of each cohort at baseline were collected locally and analysed for their fibre and antioxidant content in one central laboratory. The vital status of all participants was verified at regular intervals over 25 years. RESULTS: Alcohol and fish intake were inversely related to 25-year mortality from coronary heart disease in univariate analyses. These associations became non-significant when the confounding effects of saturated fatty acids, flavonoids and smoking were taken into account. Fibre and antioxidant vitamins intake were not related to coronary heart disease mortality in either uni- or multivariate analysis. CONCLUSION: These cross-cultural analyses show that alcohol, fish, fibre and antioxidant vitamins do not explain population differences in coronary heart disease mortality, independently of saturated fatty acids and flavonoids intake and cigarette smoking.

Adult↗

PubMed1994

Are racial differences in squamous cell esophageal cancer explained by alcohol and tobacco use?

BACKGROUND: In the United States, incidence rates of squamous cell esophageal cancer are more than five times higher among black men than among white men. Reasons that might explain this large racial disparity are being sought. PURPOSE: We evaluated whether differential use of alcohol and tobacco can fully account for the excess of squamous cell esophageal cancer among U.S. blacks. METHODS: We conducted a population-based, case-control study with in-person interviews with 373 squamous cell esophageal cancer case patients (124 white males and 249 black males) and 1364 control subjects (750 white males and 614 black males) from three U.S. geographic areas. Histologically confirmed cases of squamous cell esophageal cancer newly diagnosed from August 1, 1986, through April 30, 1989, among white and black men aged 30-79 years were included. RESULTS: Alcohol use of more than one drink per day and/or current cigarette use of at least one pack per day accounted for 92.7% (95% confidence interval [CI] = 86.8%-98.5%) of the squamous cell esophageal cancers in blacks, versus 86.3% (95% CI = 75.5%-97.1%) in whites, and for 94% of the difference between the black and white annual incidence rates. The interaction between race and the continuous drinking/smoking variable in a logistic regression analysis was statistically significant (two-sided, P = .02). Exposure rates among controls at all levels of combined alcohol and tobacco use examined were slightly higher among blacks and accounted for a small portion of the racial differences in incidence rates. CONCLUSION: Although the vast majority of esophageal cancers in both blacks and whites in our data can be explained by use of alcohol and tobacco, it is not clear why heavy consumption of alcohol and/or tobacco is responsible for 14.9 per 100,000 per year more cases of squamous cell esophageal cancer among blacks than among whites. The differences in the odds ratios appear to account for more of the racial differences in incidence rates than do the prevalences of exposure to alcohol and tobacco alone. The reasons for this apparent racial difference in carcinogenic risk from the same level of alcohol and tobacco use are unknown, but they may include qualitative differences in alcohol consumption, differences in other environmental exposures that interact with alcohol and/or tobacco to modify risks, or differences in susceptibility to these factors.

Adult↗

PubMed1995

A challenge to the concept of tubal reflux to explain the rise and fall of CA125 in serum during the first trimester.

Although amniotic fluid concentrations of cancer antigen (CA) 125 rise during the first two trimesters of pregnancy, the serum concentrations of CA125 peak during the first trimester and drop to non-pregnant values in the second and third trimester. A previous hypothesis to explain this phenomenon was that in the early first trimester decidual CA125 gains access to the maternal compartment via 'tubal reflux' and subsequent absorption by peritoneal lymphatics. However, as pregnancy advances, the decidua capsularis fuses with the decidua parietalis, thus obliterating the endometrial cavity at 10-12 weeks; the Fallopian tubes thus become functionally obstructed. To test this hypothesis, we evaluated early first trimester CA125 concentrations in women conceiving by in-vitro fertilization (IVF) and embryo transfer with patent tubes (group 1) and in those conceiving by IVF and embryo transfer with bilateral tubal occlusion (group 2). We also compared those conceiving with human menopausal gonadotrophin therapy for ovulation induction without assisted reproduction (group 3) and those conceiving without fertility drugs in assisted reproduction (group 4). Mean CA125 concentrations were similar in groups 1-3; the mean CA125 concentration in group 4 was lower but this difference was not statistically significant, probably due to the small sample size. These data do not support the concept that tubal reflux explains the rise and fall of serum concentrations of CA125, since these were equal in IVF conceptions with or without tubal patency.

CA-125 Antigen↗

PubMed1985

Increased daily sperm production in the breeding season of stallions is explained by an elevated population of spermatogonia.

Seasonal variation in number of spermatogonia and germ cell degeneration was evaluated to determine which mechanism might explain seasonal differences in daily sperm production per testis (DSP/testis) or per g parenchyma (DSP/g) in stallions. Comparing 28 adult stallions (4 to 20 yr old) in each of the nonbreeding (December-January) and breeding (June-July) seasons, the population of type A spermatogonia was more than two times greater (P less than 0.01) in the breeding season. While the number of type B spermatogonia also was elevated (P less than 0.01) in the breeding season, the number of type B spermatogonia/type A spermatogonium was similar (P greater than 0.05) between seasons. Daily sperm production/testis based on each cell type from type B spermatogonia to spermatids with elongated nuclei was lower (P less than 0.01) in the nonbreeding season. Based on DSP/g, there was significant degeneration during the meiotic divisions in the nonbreeding season. However, this reduction in potential spermatozoan production was not significant (P greater than 0.05) when considering DSP/testis. Significant germ cell degeneration also occurred in the breeding season between type B spermatogonia and primary spermatocytes. However, the type A spermatogonial population was sufficiently elevated to override this degeneration and to explain elevated production of sperm in the breeding season of stallions.

Animals↗

PubMed1996

What does not explain the variation in the direct costs of graduate medical education.

BACKGROUND: There is considerable variation in the costs of training residents across hospitals. Previous studies have reported training costs that ranged for $7,500 to $200,000 per resident, with means in the $50,000 to $60,000 range. This paper examines the factors associated with the variation in the direct costs of residency education across hospitals. METHODS: Hospital costs, hospital payment rates, various cost-of-living indices, and hospital characteristics for all hospitals in the United States receiving Medicare funds for residency education in fiscal year 1991 were obtained from various public sources. Bivariate and multivariate analyses were performed to determine whether organizational structure of residency training, specialty mix of residents, quality of training, cost of living in the geographic area, patient mix of the hospital, or other factors could explain some or all of the cost variation. RESULTS: Only a small proportion of the variation in the costs of training residents or payments for residency education could be explained by the factors analyzed. CONCLUSION: Much of the current variation in residency costs and payments is attributable to accounting and not structural or locational factors. Institutions looking for ways to become more efficient could compare costs of training across institutions without sophisticated adjusters. Federal policymakers should consider a national payment rate per resident to replace the current system based on hospital-specific costs. This proposal would redistribute dollars across residency programs. The proposal would affect payments for direct medical education in the Medicare program and could form the basis for payment for residency education by all payers.

Accounting↗

PubMed1996

The importance of comorbidities in explaining differences in patient costs.

OBJECTIVES: The authors examine to what extent comorbidities contribute to differences in patient hospital costs. METHODS: The medical record data for this study were collected from 15 metropolitan Boston hospital for 4,439 patients admitted mostly in 1985 for one of eight common conditions. Massachusetts hospital discharge abstract data for 1985 and 1993 also were used. Comorbidities were identified from the medical record for the 15-hospital data set and from discharge abstracts for all cases. Stepwise regression models were used to develop comorbidity scores. RESULTS: Across all conditions, the medical record-based comorbidity score increased the R2 value from .42 in a model with diagnosis-related groups alone to .50. In condition-specific analyses, including the comorbidity score increased the R2 by more than 50% in six of eight conditions, and was more important than several other dimensions of severity in explaining condition-specific costs. When comorbidities were determined from discharge abstract data rather than medical records, only approximately half as much comorbidity was found. Also, there was much less explanatory power: the all-condition R2 only went from .42 to .44. However, a comorbidity score developed from statewide hospital discharge abstract data was more useful in explaining variations in charges in the eight condition-specific analyses conducted on patients 65 years and older. CONCLUSIONS: Comorbidities, particularly when determined from the medical record, are important determinants of patient costs.

Adolescent↗

PubMed1995

'Dynamics of neuronal interactions' cannot be explained by 'neuronal transients'.

In a recent paper, Vaadia et al. demonstrated that patterns of firing correlation between single neurons in the cortex of behaving monkeys can be modified within a fraction of a second. These changes occur in relation to sensory stimuli and behavioral events, and even without modulations of the neurons' firing rates. These findings call for a revision of prevailing models of neural coding that solely rely on single neuron firing rates. In a defense of these models, Friston put forward an alternative explanation, proposing that the observed correlation dynamics emerge solely from co-modulations of the firing rates of each of the neurons, while the strength of their interaction remains constant. To test this possibility we re-examined the data, adopting Friston's 'neuronal transients' model, and the associated equations and procedures. We found that, to explain the dynamic correlation between a pair of neurons, the alternative interpretation requires that each neuron's response to a single stimulus is composed of a relatively large number of independent components, which co-vary with their counterparts in the companion neuron. This large number of components and their shapes lead us to conclude that, although in principle possible, the neuronal transients model: (i) does not provide a simpler explanation of the experimental results; and (ii) cannot explain these results without itself deviating significantly from most rate code models.

Animals↗

PubMed2004

Genomic regionality in rates of evolution is not explained by clustering of genes of comparable expression profile.

In mammalian genomes, linked genes show similar rates of evolution, both at fourfold degenerate synonymous sites (K4) and at nonsynonymous sites (KA). Although it has been suggested that the local similarity in the synonymous substitution rate is an artifact caused by the inclusion of disparately evolving gene pairs, we demonstrate here that this is not the case: after removal of disparately evolving genes, both (1) linked genes and (2) introns from the same gene have more similar silent substitution rates than expected by chance. What causes the local similarity in both synonymous and nonsynonymous substitution rates? One class of hypotheses argues that both may be related to the observed clustering of genes of comparable expression profile. We investigate these hypotheses using substitution rates from both human-mouse and mouse-rat comparisons, and employing three different methods to assay expression parameters. Although we confirm a negative correlation of expression breadth with both K4 and KA, we find no evidence that clustering of similarly expressed genes explains the clustering of genes of comparable substitution rates. If gene expression is not responsible, what about other causes? At least in the human-mouse comparison, the local similarity in KA can be explained by the covariation of KA and K4. As regards K4, our results appear consistent with the notion that local similarity is due to processes associated with meiotic recombination.

Animals↗

PubMed1993

Degree of breast emptying explains changes in the fat content, but not fatty acid composition, of human milk.

We compared within and between breastfeed changes in milk fat to short-term rates of milk synthesis and degree of breast emptying (measured using the Computerized Breast Measurement system) over two 24 h periods for five lactating mothers. The fat content (f) of fore and hind milk samples increased more steeply as the breast was progressively emptied by the infant (degree of emptying, d, range 0-1; f = 21.59 + 9.38d + 70.99d2; P < 0.0001; r2 = 0.68; n = 154). For the nine individual breasts, between 41-95% of the variance of the fat content of milk was explained by degree of breast emptying. We argue that this relationship explains differences in the circadian rhythm of the fat content of milk and allows the accurate calculation of the average fat content of milk consumed by infants (37-66 g/l for the nine individual breasts). The fatty acid composition of the fore and hind milk samples was determined for four of the mothers. We observed within and between breastfeed variability in the relative proportions of the seven major fatty acids of milk fat and these changes are discussed with reference to the control of fat synthesis in the human mammary gland.

Breast↗

PubMed1991

Explaining outputs of primary health care: population and practice factors.

OBJECTIVE: To examine whether variations in the activities of general practice among family health service authorities can be explained by the populations characteristics and the organisation and resourcing of general practice. DESIGN: The family health services authorities were treated as discrete primary health care systems. Nineteen performance indicators reflecting the size, distribution, and characteristics of the population served; the organisation of general practice (inputs); and the activities generated by general practitioners and their staff (output) were analysed by stepwise regression. SETTING: 90 family health services authorities in England. MAIN OUTCOME MEASURES: Rates of cervical smear testing, immunisation, prescribing, and night visiting. RESULTS: 53% of the variation in uptake of cervical cytology was accounted for by Jarman score (t = -3.3), list inflation (-0.41), the proportion of practitioners over 65 (-0.64), the number of ancillary staff per practitioner (2.5), and 70% of the variation in immunisation rates by standardised mortality ratios (-6.6), the proportion of practitioners aged over 65 (-4.8), and the number of practice nurses per practitioner (3.5). Standardised mortality ratios (8.4), the number of practitioners (2.3), and the proportion over 65 (2.2), and the number of ancillary staff per practitioner (-3.1) accounted for 69% of variation in prescribing rates. 54% of the variation in night visiting was explained by standardised mortality ratios (7.1), the proportion of practitioners with lists sizes below 1000 (-2.2), the proportion aged over 65 (-0.4), and the number of practice nurses per practitioner (-2.5). CONCLUSIONS: Family health services authorities are appropriate systems for studying output of general practice. Their performance indicators need to be refined and to be linked to other relevant factors, notably the performance of hospital, community, and social services.

England↗

PubMed1993

Explaining socioeconomic differences in sickness absence: the Whitehall II Study.

OBJECTIVE: To describe and explain the socioeconomic gradient in sickness absence. DESIGN: Analysis of questionnaire and sickness absence data collected from the first phase of the Whitehall II study. Grade of employment was used as a measure of socioeconomic status. SETTING: 20 civil service departments in London. SUBJECTS: 6900 male and 3414 female civil servants aged 35-55 years. MAIN OUTCOME MEASURES: Rates of short spells (< or = 7 days) and long spells (> 7 days) of sickness absence. RESULTS: A strong inverse relation between grade of employment and sickness absence was evident. Men in the lowest grade had rates of short and long spells of absence 6.1 (95% confidence interval 5.3 to 6.9) and 6.1 (4.8 to 7.9) times higher than those in the highest grade. For women the corresponding rate ratios were 3.0 (2.3 to 3.9) and 4.2 (2.5 to 6.8) respectively. Several risk factors were identified, including health related behaviours (smoking and frequent alcohol consumption), work characteristics (low levels of control, variety and use of skills, work pace, and support at work), low levels of job satisfaction, and adverse social circumstances outside work (financial difficulties and negative support). These risk factors accounted for about one third of the grade differences in sickness absence. CONCLUSION: Large grade differences in sickness absence parallel socioeconomic differences in morbidity and mortality found in other studies. Identified risk factors accounted for a small proportion of the grade differences in sickness absence. More accurate measurement of the risk factors may explain some of the remaining differences in sickness absence but other factors, as yet unrecognised, are likely to be important.

Absenteeism↗

PubMed1994

Changes in risk factors explain changes in mortality from ischaemic heart disease in Finland.

OBJECTIVES: To estimate the extent to which changes in the main coronary risk factors (serum cholesterol concentration, blood pressure, and smoking) explain the decline in mortality from ischaemic heart disease and to evaluate the relative importance of change in each of these risk factors. DESIGN: Predicted changes in ischaemic heart disease mortality were calculated by a logistic regression model using the risk factor levels assessed by cross sectional population surveys, in 1972, 1977, 1982, 1987, and 1992. These predicted changes were compared with observed changes in mortality statistics. SETTING: North Karelia and Kuopio provinces, Finland. SUBJECTS: 14,257 men and 14,786 women aged 30-59 randomly selected from the national population register. MAIN OUTCOME MEASURES: Levels of the risk factors and predicted and observed changes in mortality from ischaemic heart disease. RESULTS: The observed changes in the risk factors in the population from 1972 to 1992 predicted a decline in mortality from ischaemic heart disease of 44% (95% confidence interval 37% to 50%) in men and 49% (37% to 59%) in women. The observed decline was 55% (51% to 58%) and 68% (61 to 74) respectively. CONCLUSION: An assessment of the data on the risk factors for ischaemic heart disease and mortality suggests that most of the decline in mortality from ischaemic heart disease can be explained by changes in the three main coronary risk factors.

Adult↗

PubMed1995

Do changes in cardiovascular risk factors explain changes in mortality from stroke in Finland?

OBJECTIVES: To estimate the extent to which the changes in the main cardiovascular risk factors (blood pressure, smoking, and serum cholesterol concentration) can explain the observed changes in mortality from stroke in Finland during the past 20 years. DESIGN: Predicted changes in mortality from cerebrovascular disease mortality were calculated by a proportional hazards model from data obtained in cross sectional population surveys in 1972, 1977, 1982, 1987, and 1992. Predicted changes were compared with the observed changes in mortality statistics. SETTING: North Karelia and Kuopio provinces, Finland. SUBJECTS: 16,741 men and 16,389 women aged 30-59 randomly selected from the national population register, of whom 14,054 men and 14,546 women participated. MAIN OUTCOME MEASURES: Levels of risk factors and predicted and observed changes in mortality from cerebrovascular disease. RESULTS: The observed changes in diastolic blood pressure, total serum cholesterol concentration, and smoking in the population from 1972 to 1992 predicted a 44% fall in mortality from stroke in men and changes in diastolic blood pressure and smoking predicted a 34% fall in women. The observed fall in mortality from stroke was 66% in men and 60% in women. CONCLUSIONS: Two thirds of the fall in mortality from stroke in men and half in women can be explained by changes in the three main cardiovascular risk factors.

Adult↗

PubMed1994

Failure of cigarette smoking to explain international differences in mortality from chronic obstructive pulmonary disease.

STUDY OBJECTIVE: The study aimed to explain international differences in rates and trends of chronic obstructive pulmonary disease (COPD) using two measurements of cigarette smoking, the major risk factor for this disease. DESIGN: Mortality data for COPD were obtained from the World Health Organisation for 31 countries from 1979 to 1988. Smoking data were obtained for most countries. COPD rates were compared to the percentage of current smokers and past levels of cigarette consumption. COPD trends were compared to past consumption trends. MAIN RESULTS: In men, Romania had the highest COPD mortality and Greece the lowest throughout the period. English speaking countries occupy most of the other top positions, and southern European countries and Japan the low positions. Women show a similar ranking to men (r = 0.75; p < 0.01 (1988)). Mortality rates in men are, in general, two to four times those in women. Most countries show either a decrease or no change in COPD mortality over the period. In women the opposite is true--no clear relationships are seen when comparing rates and trends of COPD with measures of smoking. CONCLUSION: This failure to explain international COPD differences suggests that national data on COPD may be unreliable or national cigarette smoking data are inadequate, or both.

Adult↗

PubMed1996

Can regional variation in "avoidable" mortality be explained by deaths outside hospital? A study from Sweden, 1987-90.

STUDY OBJECTIVE: This study aimed to calculate the proportion of deaths outside hospital in Sweden for some conditions for which the acute medical management may be important to the outcome and to analyse whether the proportion of deaths outside hospital can explain regional variations in mortality from these causes of death. DESIGN: The place of death was registered on all death certificates in Sweden during the period 1987-90. The proportion of deaths outside hospital was calculated at the national level for selected causes of death. Variation in cause-specific mortality among the 26 administrative health areas in Sweden was analysed. Death rate ratios were calculated with standardisation for age and sex using the national rate as standard. The correlation between the proportion of deaths outside hospital in each health area and the cause specific mortality irrespective of place of death was calculated. For areas with a significantly high death rate the ratios for mortality outside hospital as well as in hospital were analysed in order to decide which component of mortality represented a high mortality risk. SETTING AND PARTICIPANTS: All death registration in Swedish citizens and other residents in Sweden aged under 70 years between 1987 and 1990 which gave diabetes, asthma, ischaemic heart disease, cerebrovascular diseases, or ulcer of the stomach or duodenum as the underlying cause of death. MAIN RESULTS: For asthma (58%) and ischaemic heart disease (54%), most deaths occurred outside hospital. For most causes of death, however, no correlation was found among the health areas between the proportion of deaths outside hospital and the SMR for mortality irrespective of the place of death. A high death rate was associated with a high proportion of deaths outside hospital, for diabetes in one area in the north of Sweden (Norrbotten) and for ulcer of the stomach and duodenum in one large municipality (Göteborg). CONCLUSIONS: The high proportion of deaths outside hospital at the national level for some of the conditions studied suggests that in-depth studies of the process preceding death and the functioning of medical care are needed. In most cases, however, no evidence was found that regional variation in mortality could be explained by death outside hospital. The results for diabetes in Norbotten and ulcer of stomach and duodenum in Göteborg indicate that in-depth studies on the quality of care are required.

Adolescent↗

PubMed1990

Xenon kinetics in muscle are not explained by a model of parallel perfusion-limited compartments.

Experimental tissue gas kinetics do not follow the prediction for a single stirred perfusion-limited compartment. One hypothesis proposes that the kinetics might be explained by considering the tissue as a collection of parallel compartments, each with its own flow, reflecting the tissue microcirculatory flow heterogeneity. In this study, observed tissue gas kinetics were compared with the kinetics predicted by a model of multiple parallel compartments. Gas exchange curves were generated by recording the time course of tissue radioactivity in the intact calf muscles of anesthetized ventilated dogs exposed to step function changes of 133Xe in the inspired air for 5-h periods. Microcirculatory flow heterogeneity in the same tissue was determined by the radioactive microsphere method. Observed mean tissue transit times were on average longer than predicted by a factor of 6.7. Observed means averaged 52.1 min compared with 8.3 min predicted by the perfusion-limited model. Relative dispersions of tissue transit times were also uniformly larger than predicted. We conclude that Xe gas kinetics in intact canine skeletal muscle are not explained by a model of multiple parallel perfusion-limited compartments. Countercurrent exchange of gas between vessels is a possible explanation.

Animals↗