Cross-sectional studies are descriptive observational epidemiological studies which investigates the prevalence or occurrence of a disease in a given community/population. It is the most straightforward type of observational epidemiological study in the sense that it examines a cross-section of a community at one particular point in time and, extrapolates the results of the study to the entire population once the sampling of cross-section of participants is adequately undertaken. Cross-sectional study can also be called disease-frequency or prevalence study. It assesses the disease and exposure at the same point in time, thus cross-sectional study cannot always discriminate whether the presence of the disease affected the individual’s exposure to it or whether the exposure heralded the disease development. Prevalence studies are often carried out in a population to determine the category of people that are suffering from a particular disease, when the disease occurred and where it is occurring. Such studies are barely used for testing a hypothesis; rather they are very useful in raising alarm about the relationship between a disease and exposure, thus assessing the healthcare needs of a given community.
Cross-sectional studies unlike other types of studies (case-control and cohort studies) provides information about a disease on an entire population by understudying the population since only a small fraction of members of that population (i.e. a cross-section) are actually recruited for the study. It should be noted that both case-control and cohort studies are population epidemiological studies while prevalence studies only measures current exposure level in relation to current disease status in a population since its participants (or subjects for the study) are only selected on these two basis (i.e. current disease status and current exposure rate). Cross-sectional studies generally make use of already established data such as that from a hospital record; and when such information are not available; then questions on when, where and persons affected by the disease will be asked by the investigator as a clue to measuring the exposure prevalence of a disease in relation to the disease prevalence in the population.
MERITS OF CROSS-SECTIONAL STUDIES
- Prevalence studies can be taken as census studies.
- They identify the existence of health problems in a population.
- They present a highly generalized result when the study is based on a sample of the general population.
- They are cost-effective or inexpensive in that they can be carried out in a relatively short period of time.
- They yield prevalence, and thus can be used to explain the incidence of a disease in a population.
- They are very simple to conduct, and they do not require a follow-up of the study participants.
DEMERITS OF CROSS-SECTIONAL STUDIES
- Cross-sectional studies cannot tell which came first between exposure and disease. They only study current disease occurrence without taking into cognizance obsolete data regarding the same disease.
- They cannot identify the cause-effect relationship of a disease.
- Cross-sectional studies identify a high proportion of prevalent cases of long duration without looking at those who may have died or recovered from the disease being studied.
- It is not feasible for the study of rare diseases (e.g. cancer) and cannot establish the sequence of events in a disease outbreak.
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