Case-control studies compare subjects who have a condition (cases) to similar subjects who do not (controls) to identify factors that may contribute to a disease or risk factor. They are useful when experiments are impossible or unethical, and are a relatively inexpensive way to study rare diseases. Advantages include studying rare factors and providing quick, cheap results, but they are prone to bias and recall errors. A case-control study example identified smoking as linked to lung cancer by interviewing patients.

1. UNIT-4
EPIDEMIOLOGY
CASE CONTROL STUDY
SUBMITTED TO: SUBMITTED BY:
DR. ANJALATCHI MEHAK SAINI
M.SC.(N) MD(AM) MBA(HA) M.SC. NURSING 1ST YEAR
ERA COLLEGE OF NURSING ERA COLLEGE OF NURSING

2. LEARNING OBJECTIVES
 AT THE END OF THE LECTURE THE STUDENT WILL:
• DEFINE CASE CONTROL STUDIES
• KNOW THE INDICATIONS FOR CASE CONTROL STUDIES
• KNOW THE ADVANTAGES AND DISADVANTAGES OF C/ C
STUDIES COMPARED TO OTHER EPID. STUDIES
• KNOW THE STEPS FOR CARRYING OUT C/C STUDIES
• NARRATE AT LEAST ONE EXAMPLE OF A C/C STUDY

3. ABBREVIATIONS USED:
C/C STUDIES= CASE CONTROL STUDIES

4. DEFINITION
Case-control studies are studies used to
identify factors that may contribute to a
disease or risk factor by comparing subjects
who have that condition (the 'cases') with
patients who do not have the condition but
are otherwise similar (the 'controls').

5. INDICATIONS FOR C/C STUDIES
 For establishing cause-and-effect relationships, e.g., between
types of sexual behavior and developing cervical cancer
 Instances in which experiments (ideal) would be impossible,
impractical, and/or unethical.
 Case-control studies are a relatively inexpensive and
frequently-used type of epidemiological study that can be
carried out by small teams or individual researchers in single
facilities in a way that more structured experimental studies
often cannot be.

6. ADVANTAGES OF C/C STUDIES
 Case-control studies use patients who already have a disease
or other condition and look back to see if there are
characteristics in these patients that differ from those who
don’t have the disease.
 Good for studying rare diseases or risk factors. In case of rare
disease, studies, which rely on government funding, are
unlikely to be supported because of the low likelihood that
the population will develop the disease.
 Provides a cheaper and quicker study of risk factors.

7. DISADVANTAGES OF C/C STUDIES
They do not give any indication of the absolute risk
of the factor in question. For instance, a case-control
study may tell you that a certain behavior may be
associated with a tenfold increased risk of death as
compared with the control group. Although this
sounds alarming, it would not tell you that the actual
risk of death would change from one in ten million to
one in one million, which is quite a bit less alarming.
For that information, data from outside the case-
control study must be consulted.

8. They are rated as low quality, grade 3, on a
standard scale of medical evidence.

9.  A further problem is that case-control studies depend on
correct and honest reporting of the risk factor, which may be
many years in the past (recall bias) or may be seen socially
undesirable. Case-control studies can be biased if the risk
factor inquired about is incorrectly reported.
 Selection bias is also high: the difference between selection of
study and control groups
 Case-control studies are a valuable investigative tool,
providing rapid results at low cost, but caution should be
exercised unless results are confirmed by other, more robust
evidence.

10. STEPS IN C/C STUDY
 Select the research problem
 Review literature
 State the research problem
 State the hypothesis to be tested
 Write the objectives
 Choose whether retrospective or prospective c/c study
 Select the cases
 Select the controls
 Collect data, analyze and write report and publish

11. EXAMPLE OF A C/C STUDY
In 1950 Sir Richard Doll and his colleagues
interviewed 700 lung cancer patients from 20
hospitals in London, asking them about their
smoking habits and any other questions they
thought might link. This was no proper control group
but he was able to find that tobacco was the only
common factor in all these patients.