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PubMed1999

Individual causal models and population system models in epidemiology.

A group of individuals behaves as a population system when patterns of connections among individuals influence population health outcomes. Epidemiology usually treats populations as collections of independent individuals rather than as systems of interacting individuals. An appropriate theoretical structure, which includes the determinants of connections among individuals, is needed to develop a "population system epidemiology." Infection transmission models and sufficient-component cause models provide contrasting templates for the needed theoretical structure. Sufficient-component cause models focus on joint effects of multiple exposures in individuals. They handle time and interactions between individuals in the definition of variables and assume that populations are the sum of their individuals. Transmission models, in contrast, model interactions among individuals over time. Their nonlinear structure means that population risks are not simply the sum of individual risks. The theoretical base for "population system epidemiology" should integrate both approaches. It should model joint effects of multiple exposures in individuals as time related processes while incorporating the determinants and effects of interactions among individuals. Recent advances in G-estimation and discrete individual transmission model formulation provide opportunities for such integration.

Causality↗
PubMed2000

Equipment malfunctions and attribution of causality.

The purpose of this study was to test whether individuals would be more likely to attribute the cause for the malfunction of a new piece of equipment as a manufacturing problem in the equipment or as an inability on their part to properly work with the equipment. The subjects were 600 residents of Florida, selected by a stratified random sample and interviewed in a statewide telephone survey. Subjects were more likely to attribute the cause to themselves rather than the machine. Overall, 71% attributed the cause to themselves, while only 24% said the machine was at fault. There was also an interaction effect in terms of income, with middle-income users more likely to blame the machine and upper-income users more likely to blame themselves. Further, there was also a significant relationship between attribution of cause and age, with older respondents being more likely to attribute cause to themselves. These results imply that attribution may differ when the potential object of attribution is a machine rather than another person.

Adolescent↗
PubMed1999

Credit programs for the poor and reproductive behavior in low-income countries: are the reported causal relationships the result of heterogeneity bias?

Group-based lending programs for the poor have drawn much attention recently. As many of these programs target women, an important research question is whether program participation significantly changes reproductive behavior and whether the gender of the participant matters. Using survey data from 87 Bangladeshi villages, we estimate the impact of female and male participation in group-based credit programs on reproductive behavior while attending to issues of self-selection and endogeneity. We find no evidence that women's participation in group-based credit programs increases contraceptive use or reduces fertility. Men's participation reduces fertility and may slightly increase contraceptive use.

Adult↗
PubMed2000

[Causal interactions of estrogens and alcohol in cancer of the breast].

BACKGROUND: The majority of studies and meta-analyses tend to show a very slight increase of risk of beast cancer in post-menopausal women receiving hormone replacement therapy (HRT). Such results must however be interpreted in light of biases including intensive follow-up in women taking HRT and unknown or new parameters. DATA: Several publications have demonstrated an increased relative risk of breast cancer in women consuming alcohol. This increase rises linearly with the level of alcohol intake. To date, this parameter has been neglected in post-menopausal women taking HRT. Two studies have demonstrated a rise in breast cancer in women taking HRT who drink alcohol. No particular explanation is put forward. INTERPRETATION: Based on an experimental human study, E. Ginsburg has shown that there is a considerable and long-duration increase in estradiolemia in women on HRT who also drink alcohol. This hyperestradiolemia could exceed the promotion threshold of breast carcinogenesis. This new parameter must be taken into consideration as effective preventive measures can be implemented: convincing women taking HRT to limit their alcohol intake.

Alcohol Drinking↗
PubMed1999

[Hyperglycemia and atherosclerosis. Causal relation or association?].

Hyperglycemia may lead to atherosclerosis by different pathogenic mechanisms. Nonenzymatic glycation and oxidation of LDL may increase its atherogenicity. Glycation may modify some arterial wall structural proteins. Increased blood glucose leads to hypertriglyceridemia which results in decrease of HDL-cholesterol level and in increase of atherogenic dense LDL particles. Hyperglycemia also adversely affects processes of platelet aggregation, hemocoagulation and fibrinolysis. It accelerates the development of diabetic nephropathy--a condition with a high prevalence of macrovascular diseases. Prospective epidemiologic studies have shown that diabetic patients in worse metabolic control had an increased cardiovascular morbidity and mortality. Therapeutic randomized studies in type 1 (DCCT) and type 2 (UKPDS) diabetic patients have shown that better diabetes control had a preventive effect against development of microvascular complications. The incidence of macrovascular complications both in type 1 diabetic patients on intensive insulin or sulfonylurea treatment has been decreased on the level of borderline statistical significance. Metformin lead to a significant decrease in myocardial infarction incidence in the subgroup of obese type 2 diabetic patients. In conclusion, maximal possible metabolic control of diabetes prevents the development of microvascular complication, but more impressive decrease in macrovascular disease incidence probably requires to affect another important risk factors for atherosclerosis, such as dyslipidemia and hypertension.

Arteriosclerosis↗
PubMed2001

[Causality and psychopathological course in a cannabis dependency case].

We analyzed the behavior of teenagers who use cannabis in order to identify the drive leading to cannabis abuse and the perceived benefit which apparently sustains dependency. This analysis pointed out the following issues: identification, alterity modulation, modification of thinking activity, pursual of a psychopathological state of deterioration. This short clinical dissertation should be completed by further more deeply oriented clinical research.

Adolescent↗
PubMed2001

[Causal factors of decline disease in exotic pine (Pinus taeda and P. elliottii) plantations].

Investigation on the cause of the decline of exotic pine plantations in Anhui Province was carried out from 1995 to 2000. The results showed that the cause might develop from the interaction of three or more sets of factors. The first group of factors called as predisposing factors were high and low temperature and rainfall, poor soil fertility, and excessive soil bulk density, soil moisture, and of stand density; the second group of factors called as inciting factors were insect defoliators, damaging diseases of needles, late spring frost, severe drought, and excessive resin-tapping, and the third group of factors called as contributing factors were several biotic agents such as shoot blight infected by Sphaeropsis sapinea, decay wood and root rot by fungi, and bark beetles and wood borers.

Causality↗