One of two major approaches in conducting epidemiological
investigations involves observation of the disease, drug use problem,
or other phenomenon of interest. The other major approach, called experimental epidemiology, is discussed in Chapter 4.
Study designs used in observational epidemiology include case
reports, cross-sectional studies, case-control studies, and cohort
studies. Studies can be designed to be retrospective or prospective.
In all of these study designs, sampling, or how people are or are
not chosen to be studied, is an important issue. It is a primary
way to differentiate among designs. In this chapter, each of the major
observational study designs is described, and the process for conducting
them is outlined.
Observational study designs in pharmacoepidemiology produce data
and information that identify the occurrence of drug use problems
and that test hypotheses regarding the probable reasons or causes
of these problems. In some instances, instead of a problem resulting
from drug use, new beneficial uses for a drug product might be identified
for further investigation in clinical trials.
Each epidemiological investigation follows the same general rules
of research design and methodology. First, the problem must be identified
or the research question must be stated. Dependent variable(s),
the outcome(s), and the independent variable(s) are identified.
The causes or things associated with the disease or drug use problem
are the independent variables. Second, cases are defined, or populations
at risk are sampled. Other steps in the process include identifying
and collecting all of the relevant data and information, analyzing
the data according to the study hypotheses or research questions,
and interpreting the results. Analysis may include subdividing the population
according to a certain risk factor and comparing rates for each
Epidemiological study designs also can be described according
to a number of different aspects. One aspect is whether the study
is observational or experimental. Investigators in observational studies
may plan and identify variables to be measured, but human intervention
is not a part of the process. Experimental studies, in contrast,
involve intervention in ongoing processes to study any resulting
change or difference. Epidemiological studies are also descriptive
or analytical in nature. Descriptive studies attempt to uncover
and portray the occurrence of the condition or problem, whereas
analytical studies determine the causes of the condition or problem.
Observational epidemiology provides information about disease
patterns or drug use problems by various characteristics of person,
place, and time. This approach is used by public health professionals
for efficient allocation of resources and to target populations
for education, prevention, and treatment programs. It also is used
by epidemiologists to generate hypotheses regarding the causes of
disease or drug use problems. Some researchers do not consider experimental
studies to be true epidemiological studies in the traditional sense
because they follow clinical or planned research designs. Descriptive
studies provide insight, data, and information about the course
or patterns of disease or drug use problems in a population or ...