The word epidemiology has its origin from the Greek and is distinguished into three words; epi standingfor on then demos (people) and finally logos (study). In general this term deals with the study of what a given population is facing. Epidemiology is the study of identification of health issues within a given population and using the study to control the disease. It also tries to acknowledge a positive health condition. The epidemiology tries to focus on its study on a specific population within a given specific geographical area, and it should be within a specific time and a given country, but also sex,age must also be considered a good example is “survival for the tuberculosis patients from the age of 40 and non patients among the women born in 1963-1983.” The study borrows its principle from the media where they always use the 5w but in this case they use 3ws that is who is affected by the disease, where and when the disease is taking place and within the given population. After taking the data is then keenly studied and estimates are done on the spread of the disease and how the disease is controlled.
Public health has its basics from epidemiology since it depends on the use of probability, statistics and the research methods. It also borrows from the scientific disciplines to explain the health related conditions state and this explain the importance of public health to this field since their action is based on the reasoning and science. The study of epidemiology mostly is concerned with the spread of the disease but not the treatment of the disease just like a preventive medicine, this is a program the tries to check on the effect of the disease to the population thus those whore are receiving the prevention to those that are not receiving the preventive medicine. Through this the preventive measures that have been carried out can be determined.
Data sources for;
The age –standardized morbidity, the hospital admissions and the discharges, the cancer registration of disease events and finally outpatient and the primary health care consultations
Prevalence selected disabling conditions.
The international classification of functioning. Disability and health care (ICF) has been able to achieve this by looking at those who are unable to work and the ones having difficulty in studying on those who are not able to read and looking at those unemployed.
The data source is on the number of mertanal deaths in a given year within the geographic area and also the number of live births which occurred among the population of the given geographic area within that same year.
An example to explain this is the case of the study carried out to show the relationship between the alcohol consumption and the liver treatment within four countries in African continent, if the result shows that countries with a increased rate of consumption of alcohol had higher rates of liver operation, and the investigator decides to conclude that those who consumed alcohol actually had high rate of liver problems then that would be the ecological fallacy since the correlations differs between two ecological variables, within the same population on the individuals.
It is the other term for prevalence studies, and it is a study that an individual’s status regardless of the presence or absence with regards to exposure and disease is assessed at a specific time. And due to both exposure and disease at the same time it is difficult to create a difference on whether the exposure of the disease comes before the disease development and if the disease availability influenced the level of the exposure of the disease. It mainly done to check on the presence of an association than studying on the hypothesis.
Ecologic comparison study
Comparison study is a study that tend to use the data that have been collected on a regular basis from the whole population so as to be able to make a comparison of the disease occurrence frequency between different group of individuals at the same period of time or within the same group of individuals at different time periods. These studies are mainly conducted for the hypothesis formulation but not to be used to test the hypothesis due its acquired disadvantages. This study usually represents the whole populations but not the individuals since one cannot be able to link the disease exposure to the case of disease in a single individual. Example is the case is the relationship between the alcohol consumption and the treatment procedures for the liver treatment in five counties in Canada 2008.
This is a study that tends to study the group rather than concentrating on the individuals during the hypothesis generation. To elaborate this is an example where by a relationship is found on the average sales of reproductive pills and the case of infertility and the occurrence of the unusually high rates of low population. In this observation a test must first be done in order to confirm if there are other factors leading to low population. With the use of the ecological data it can be used to make a comparison of a given population at the same time and comparing the population at different time.
In order to calculate the risk we use the (class of theexposed group was found to be with the disease divided with the whole group that was exposed) divided by( class of theunexposed group was found to be with the disease divided with the whole group that was unexposed)
CIexp = 800/ 20000 = 0.04.
CIunexp = 300/30000 =0.01
RR = 0.04/0.01 =4
Advantages of ecological study
It is always time saving thus it is able to collect data quick if the population data have always been collected on a regular basis and their availability Is guaranteed.
When it comes to association then it is a useful initial step.
When the data sequence is carried out temporarily then the data quality outcome will be poor.
Information is not useful at the hypothesis level.
Advantages of cross sectional study.
It always give rise to the yield prevalence
It is cheaper and faster when it comes to relative risk.
It can carry a study on both several outcomes and exposure at the same time.
Always has a clear control over the selection of the study subjects
Large samples are always time consuming.
It always doesn’t provide a clear scope.
Advantages of case study
It always establishes the absolute risk.
Since the outcome of the study is not always determined at the period when the exposure is measured ,the issue of biasness is done away with.
Multiple outcomes can be assessed. It is more easier to measure potential confounders as compared to case control study.
The certainty of exposure to precede the outcome is usually guaranteed.
It is always a time consuming process.
Long delays before the results are out.
ANS IS 0.957
OR(low-fat diet and colon cancer)=0.6
This study shows that the cases were 0.6 times, more likely than the control to have eaten low fat –diet. Thus this shows that the low fat diet is not the major cause of the colon cancer since the figure is low.
OR (aerobic exercise and dental caries) = 1 (not significant).
This shows that dental carries is not related to those who do the aerobic exercises.
OR (exposure to side stream cigarette smoke and lung cancer) = 1.3.
From the results the cases of lung cancer were1.3 times to have been related to the exposure to side stream cigarette smoking. This result shows that the major cause of this kung cancer is exposure to the cigarette smoking.
OR (infectious disease of the pelvis and ectopic (tubal) pregnancy) = 3.0
The case of ectopic pregnancy is 3.0 times to have been caused due to the pelvis disease infection. Thus the chances of getting an ectopic pregnancy will largely depend by the presence of the disease thus those exposed to the pelvis disease are likely to suffer from ectopic pregnancy.
The relative risk of association is the same is not the same .when It is 2.0 then it indicates that the risk among the exposed factor thus the risk is stronger but when it is 0.5 the it clearly indicates that the risk is negative and the exposure to the disease is decreased.