What is a cross-sectional study in epidemiology?
Cross-sectional studies measure the cause (exposure) and the effect (disease) at the same point in time. They compare the rates of diseases or symptoms of an exposed group with an unexposed group. Strictly speaking, the exposure information is ascertained simultaneously with the disease information.
What is an ecological study in epidemiology?
Ecological studies are epidemiological evaluations in which the unit of analysis is populations, or groups of people, rather than individuals. Individual-level variables are properties of each person whereas ecological variables are properties of groups, organizations, or places.
What is an ecologic study design?
Ecologic studies are studies in which the unit of observation is a group, not separate individuals, for one or more study variables. For example, exposure and risk factors are known only at the group level, such as the average air pollution concentration in different cities.
What is the difference between an ecological study and a cross-sectional study?
Cross-sectional studies collect the data of the exposure variable and the outcome at the same time, to describe characteristics of the sample or to study associations. Ecological studies describe and analyze correlations among different variables, and the unit of analysis is aggregated data from multiple individuals.
What is a predictive cross-sectional study?
A cross-sectional study involves looking at data from a population at one specific point in time. This method is often used to make inferences about possible relationships or to gather preliminary data to support further research and experimentation.
What are the five levels of ecological study?
Within the discipline of ecology, researchers work at five broad levels, sometimes discretely and sometimes with overlap: organism, population, community, ecosystem, and biosphere.
Is an ecological study descriptive or analytical?
Descriptive studies that examine populations, or groups, as the unit of observation are known as ecological studies. Ecological studies are particularly useful to conduct when individual-level data would either be difficult or impossible to collect, such as the effect of air pollution or of legislation.
Are ecologic studies good for rare diseases?
Ecological studies are often used to measure prevalence and incidence of disease, particularly when disease is rare. They are inexpensive and easy to carry out, using routinely collected data, but they are prone to bias and confounding.
Are ecologic studies expensive?
Ecologic Studies: A- are expensive and require a great deal of time to conduct. D- Exposure and disease histories are collected simultaneously. In case-control studies, the odds ratio is used as an estimate of the relative risk.
Can ecological studies be analytical?
Analytic models in ecologic studies are of different forms: some, but not all, variables are ecological. analyses may simultaneously include individual and ecological variables on the same construct (e.g., income). This could be called multilevel modeling, hierarchical regression, or a mixed effects modeling.
What is cross-sectional correlation?
Think of a cross-sectional study as a snapshot of a particular group of people at a given point in time. For example, a cross-sectional study might be used to determine if exposure to specific risk factors might correlate with particular outcomes.
How is secular trend related to epidemiology?
Explain the relationship between these two terms. Secular trend is a long-term trend that develops or progresses over many years. In terms of epidemiology, secular trend is described as the occurrence of disease over a prolonged period, influenced by the degree of immunity in the population.
When does a stock become a secular trend?
To be considered as such, technical analysts assign the category of secular to patterns that are consistent within at least 10 to 30 years. This is different for cyclical stocks that are more volatile and tend to shift direction many times during that same period. James Markfield is a Senior Economist at Major Bank of London.
When does a programme cause a secular trend?
A programme is considered to cause changes if it makes things happen that were not likely to be caused by the secular trend. Secular trend and risk factors for antimicrobial resistance in Escherichia coli isolates in Switzerland 1997-2007.
How are disease rates determined by the epidemiologist?
Age. In most descriptive analyses, the epidemiologist will determine disease rates by age. This can be as simple as finding that a health event is affecting only a limited age group or as complicated as comparing age-specific rates among multiple groups. Age represents three different categories of determinants of disease risk .