Vitamin Information Center

Case Control Studies
Definition
Studying infrequent events, such as death from cancer,
using randomized clinical trials or other controlled
prospective studies requires that large populations be
tracked for long periods in order to observe disease
development. Case-control studies use patients who
already have a disease or other condition and look back
to see if there are characteristics of these patients that
differ from those who don’t have the disease. The casecontrol
study provides a much cheaper and quicker
study of risk factors. If the evidence found is convincing
enough, then resources can be allocated to more “credible”
and comprehensive studies. The case-control study
begins with the identification of an outcome or effect
and a number of potential causative factors. A group
of cases which exhibit the outcome under investigation
is selected. A number of control subjects (or controls)
who do not exhibit the outcome or effect under investigation
are then chosen. These controls should match the
cases as closely as possible with respect to the non-risk
variables; this allows the proposed non-risk variables to
be ignored in the analysis. Sometimes more than one
control group is used. The case and control groups are
then compared for the proposed causal factors, and statistical
analysis is used to estimate the strength of association
of each factor with the studied outcome.
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.

Case Cohort Study
Definition
In a case-cohort study, cases are defined as those participants
of the cohort who developed the disease of interest,
but controls are identified before the cases develop.
This means that controls are randomly chosen from all
cohort participants regardless of whether they have the
disease of interest or not, and that baseline data can be
collected early in the study.
Case-cohort studies are very similar to nested casecontrol
studies. The main difference between a nested
case-control study and a case-cohort study is the way in
which controls are chosen. Generally, the main advantage
of case-cohort design over nested case-control
design is that the same control group can be used
for comparison with different case groups in a casecohort
study. The main disadvantages of the case-cohort
design is that it requires a more complicated statistical
analysis and it can be less efficient than a nested casecontrol
study under some circumstances (e. g., in studies
with long follow-up).

ATLANTA, April 14 (UPI) — U.S. researchers say they are learning how vitamins and minerals can stimulate or prevent the development of colon cancer.

Emory University researchers in Atlanta find in a study of 92 patients that supplementing a diet with calcium and vitamin D appears to increase the levels of a protein call Bax — which controls programmed cell death — that may push pre-cancerous cells to self-destruct.

In another, 200-patient, case-control study, led by Dr. Robert Bostick of Emory University, high levels of calcium and vitamin D together are associated with increased levels of E-cadherin, which moderates colon cells’ movement and proliferation.

A third study on the same 200-patients shows high levels of iron in the diet are linked to low levels of APC, a protein whose absence in colon cancer cells leads to their runaway growth.

All three studies — scheduled to be presented at the American Association for Cancer Research meeting in San Diego — use colorectal biopsy samples and are part of a larger effort to identify a portfolio of measurements which taken together could predict the risk of colon cancer.

“We want to have the equivalent of measuring cholesterol or high blood pressure, but for colon cancer instead of heart disease,” Bostick says in a statement.

ATLANTA, April 14 (UPI) — U.S. researchers say they are learning how vitamins and minerals can stimulate or prevent the development of colon cancer.Emory University researchers in Atlanta find in a study of 92 patients that supplementing a diet with calcium and vitamin D appears to increase the levels of a protein call Bax — which controls programmed cell death — that may push pre-cancerous cells to self-destruct.

In another, 200-patient, case-control study, led by Dr. Robert Bostick of Emory University, high levels of calcium and vitamin D together are associated with increased levels of E-cadherin, which moderates colon cells’ movement and proliferation.

A third study on the same 200-patients shows high levels of iron in the diet are linked to low levels of APC, a protein whose absence in colon cancer cells leads to their runaway growth.

All three studies — scheduled to be presented at the American Association for Cancer Research meeting in San Diego — use colorectal biopsy samples and are part of a larger effort to identify a portfolio of measurements which taken together could predict the risk of colon cancer.

“We want to have the equivalent of measuring cholesterol or high blood pressure, but for colon cancer instead of heart disease,” Bostick says in a statement.

Researchers at Emory University are learning how vitamins and minerals in the diet can stimulate or prevent the appearance of colon cancer.

Emory investigators will present their findings on biological markers that could influence colon cancer risk in three abstracts at the American Association for Cancer Research meeting in San Diego.

In a clinical study of 92 patients, supplementing diet with calcium and vitamin D appeared to increase the levels of a protein called Bax that controls programmed cell death in the colon. More Bax might be pushing pre-cancerous cells into programmed cell death, says Emory researcher Veronika Fedirko, who will present her team’s results (abstract 464).

Previous studies have shown that calcium and vitamin D tend to reduce colon cancer risk.

“We were pleased that the effects of calcium and vitamin D were visible enough in this small study to be significant and reportable,” Fedirko says. “We will have to fully evaluate each marker’s strength as we accumulate more data.”

The studies of colorectal biopsy samples are part of a larger effort to identify a portfolio of measurements that together can gauge someone’s risk of getting colon cancer, says Roberd Bostick, MD, MPH, professor of epidemiology at Emory’s Rollins School of Public Health.

“We want to have the equivalent of measuring cholesterol or high blood pressure, but for colon cancer instead of heart disease,” Bostick says. “These measurements will describe the climate of risk in the colon rather than spotting individual tumors or cells that may become tumors.”

More about Bostick’s plans for developing non-invasive blood or urine tests for colon cancer risk is available in an Emory Health Sciences Magazine article: http://whsc.emory.edu/_pubs/hsc/winter08/pdf/hold_out_your_finger.pdf

Another abstract from Bostick and his colleagues (565) demonstrates in a 200-patient case-control study that high levels of calcium and vitamin D together are associated with increased levels of E-cadherin, which moderates colon cells’ movement and proliferation.

A third abstract on the same case-control study (5504) shows that high levels of iron in the diet are linked to low levels of APC, a protein whose absence in colon cancer cells leads to their runaway growth.

Bostick and his colleagues are participating in a ten-year multi-center study of the effects of increased vitamin D and calcium and biomarker-guided treatment of colon cancer recurrence. The study involves almost 2,500 people nationwide who have regular colonoscopies.