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Results for “Confounding Factors, Epidemiologic”

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PubMedDate not supplied

Obstructive sleep apnea and hypertension: from correlative to causative relationship.

Sleep-disordered breathing, manifested by repetitive episodes of partial or complete cessation of breathing during sleep associated with brief arousal and autonomic activation, is estimated to affect as many as 4% of adult men and 2% of adult women. Studies conducted during the 1980s revealed a strong association between sleep-disordered breathing and hypertension. The results of these early studies, which relied on relatively small samples of patients, have been confirmed in recent years by large-scale epidemiologic studies that are controlled for all possible confounding factors. This paper reviews the evidence suggesting a causative relationship between hypertension and disordered breathing in sleep. The authors discuss the possible underlying mechanisms of the two entities and address the clinical implications of this relationship. They conclude by recommending a proactive approach to the diagnosis of breathing disorders in sleep, in order to prevent the cardiovascular sequelae of this syndrome.

Confounding Factors, Epidemiologic↗
PubMedDate not supplied

Dietary differences with green tea intake among middle-aged Japanese men and women.

BACKGROUND: Although several epidemiologic investigations have suggested a protective role of green tea against cardiovascular diseases and cancer, few studies examined how consumption of green tea was associated with intake of other dietary factors. METHODS: In the winters of 1989-1991, 880 men ages 40-49 years were randomly sampled from the general populations of five Public Health Center districts of Japan. Response rate was 72% (n = 634). A convenience sample of 373 spouses also consented to participate. They were interviewed on the frequency of consumption of green tea and 37 food items. A 3-day weighed food record was collected from a subgroup of the subjects (207 men and 164 women) to calculate daily intake of 22 nutrient variables. Consumption of the foods and nutrients was compared with three levels of green tea intake (< 1, 1-4, and > 4 cups/days) after adjustment for potential confounders. RESULTS: Among men, green tea was associated significantly with consumption of 10 foods (P < 0.05) and at borderline significance with 4 nutrients (P < 0.1). These foods and nutrients included fruits (apple, orange juice), vegetables (green, yellow, and pickled), total lipid, cholesterol, and carotene. Among women, green tea was associated with 6 foods and total energy. CONCLUSION: The results indicate that consumption of green tea is associated with diets that could modify the risks of cardiovascular diseases and cancer, especially among men. When the health effects of green tea are examined by observational epidemiologic studies, potential confounding and effect modification by other dietary factors should be controlled thoroughly.

Adult↗
PubMed2000

Epidemiology: theory, study design, and planning for education.

Many health professionals have received formal training in epidemiology; however, much of it has been limited to introductory courses at the undergraduate level. Further, continuing education for health professionals has focused historically on substantive rather than methodologic issues in epidemiology. A methodologic focus is recommended to improve continuing education for the health of the public. It is crucial to equip educators and health professionals with the necessary tools or resources to understand study design, conduct research, analyze and interpret data, and critically evaluate published research. Thus, in this article, a general overview of epidemiologic study design and some of the most common methodologic issues are presented. Issues such as confounding, effect modification, measurement error, and power and sample size are highlighted. A broader recognition of these issues by educators and health professionals may ultimately help to improve public health by facilitating effective educational interventions, proper study design, analysis, interpretation, and application of epidemiologic research.

Confounding Factors, Epidemiologic↗
PubMed1996

Effect of sucrose consumption on level of Streptococcus mutans in saliva.

The aim of the present paper was to study whether sucrose consumption may affect the level of salivary Streptococcus mutans. The study was justified by the disagreement between results of "in vitro", animal and human experiments and results of epidemiological studies made on study-populations. According to experimental research, sucrose availability promotes Streptococcus mutans selection and development in the oral cavity. On the other hand, the results of epidemiological studies run counter to these experiments. In the present study, the main reasons for this disagreement were investigated and identified. From this, an epidemiological study was performed, taking into account these potentially confounding factors. The results show that sucrose consumption is actually able to promote Streptococcus mutans selection and development in the oral cavity, thus increasing the risk of dental caries.

Child↗
PubMed1999

A review of the healthy worker effect in occupational epidemiology.

This review article aims to anatomize sources of the healthy worker effect (HWE) and to summarize advantages and limitations of several approaches frequently proposed to eliminate the HWE. Although the HWE is frequently addressed in the context of selection bias, our review suggests that the selection of occupational cohorts with advantageous health status would preferably be addressed as a source of confounding biases. The authors also conclude that the exclusion of unhealthy workers at employment and the study of active workers are the two main sources of HWE, and that the use of the general population as a comparison group in occupational epidemiology should be avoided if possible. The authors encourage investigators to make distinctions between the underlying factors related to the use of the general population as the comparison group in occupational epidemiology.

Bias↗
PubMed1992

Aspects of misclassification of confounding factors.

Misclassification of exposure in epidemiologic investigations has been extensively studied and is now well understood. In contrast, misclassification of confounding factors has been much less investigated. First, we consider a situation with confounding by age, in which misclassification is introduced through stratification of this inherently continuous variable. This misclassification turns out to be benign: 75% of the original confounding is removed by stratification into two age classes and more than 90% by using three age classes. Second, we consider a situation with serious confounding and serious misclassification of the confounding factor but no misclassification of the exposure. In this situation, the misclassification turns out to be of importance. After stratification for the misclassified confounding factor, it appears as though the exposure has a stronger effect on the incidence than the confounder, which is the reverse of the true situation.

Adult↗
PubMed2003

Causal inference from randomized trials in social epidemiology.

Social epidemiology is the study of relations between social factors and health status in populations. Although recent decades have witnessed a rapid development of this research program in scope and sophistication, causal inference has proven to be a persistent dilemma due to the natural assignment of exposure level based on unmeasured attributes of individuals, which may lead to substantial confounding. Some optimism has been expressed about randomized social interventions as a solution to this long-standing inferential problem. We review the causal inference problem in social epidemiology, and the potential for causal inference in randomized social interventions. Using the example of a currently on-going intervention that randomly assigns families to non-poverty housing, we review the limitations to causal inference even under experimental conditions and explain which causal effects become identifiable. We note the benefit of using the randomized trial as a conceptual model, even for design and interpretation of observational studies in social epidemiology.

Asthma↗
PubMed1999

Confounding by indication: an example of variation in the use of epidemiologic terminology.

Confounding by indication is a term used when a variable is a risk factor for a disease among nonexposed persons and is associated with the exposure of interest in the population from which the cases derive, without being an intermediate step in the causal pathway between the exposure and the disease. However, in the literature, the term confounding by indication is not always used consistently. The authors found three different situations in which the term has been applied or might have been used but was not: confounding by indication as protopathic bias, as confounding by severity, or as a form of selection bias. It might be helpful to limit use of the term confounding by indication to the situation in which the disease that forms the indication acts as a confounder irrespective of its severity and to apply the term confounding by severity if the severity of this disease acts as a confounder. Protopathic bias and selection bias should not be confused with these terms. The use of appropriate terms ultimately will improve communication among researchers and contribute to the clarity of their papers.

Confounding Factors, Epidemiologic↗