Understanding Studies

8/14/2019 Understanding Studies

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Understanding Studies

Jyothi prasad


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There is a study born every minute and

there are countless suckers out there ready

to believe anything that they read or hear!!!

- P.T. Barnum


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The Pluses and Minuses of Studies


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Main categories of Studies

Observational research

Primarily conducted in a natural setting to study the relationship between a specific factorand some aspect of health and illness.

Eg: Body weight of healthy woman above 50 years and older and their relationship to bloodpressure

Experimental research

Basic research generates data by investigating biochemical substances or biologicalprocesses.

Eg: How Vit E helps prevent the oxidation of LDL which is a precursor of heart disease

Population based interventional trial

Sort of a cross between observational research and Experimental research

Eg: A study of 29,000 male Finnish smokers was released a few years ago, in which thosewho took beta-carotene turned out to be more likely to develop lung cancer than those whodidnt.


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Observational Experimental

Ecological studies

Cohort studies

Case-control studies

Invitro studies

Invivo studies

Controlled studies

Randomized trials

Double blind trials

Epidemiological

studiesLaboratory studies

Controlled studies


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Epidemiological studies What are they?

Epidemiological studies investigate the overall risk of a kind of disease within

specific - groups of people

Eg: For example, an epidemiological study might investigate how diet affects

the risk of breast cancer in African-American women who live in rural areas.

scientists watch whats going on, but they dont try to change it. Strong

evidence can and does arise from epidemiological studies, but remember:

detectives cant build an ironclad case out of circumstantial evidence alone.


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Different Kinds of Epidemiological studies

1. Ecological Studies:

Usually focussed on studying large population groups epidemiology seeks to identify

possible factors that increase risk of probability of disease. This can be either

Analytical, Descriptive orCross sectional

Strengths: Ecologic studies can provide powerful clues pointing in a particular

direction, especially when they compare large populations with different diets

Weakness: Ecologic studies cant prove cause and effect. If a detective keeps noticing a certain

person near the scene of a series of burglaries, he mayconsider the person a

suspect. The Detective needs more evidence!


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2. Cohort Studies/Prospective studies

In a cohort study, scientists select the study population according to their exposure, regardless of

whether the group has the disease or health outcome being studied. The researchers then

determine the outcomes of interest and compare the results on the basis of the individuals'

exposures. Cohort studies are often referred to as prospective studies because they follow the

study population forward in time, from suspected cause to effect. An example would be dividing agroup of people on the basis of their smoking status and following them for 20 years to see if they

develop lung cancer.

Strengths: Cohort studies let researchers study people over the long period of time. A strength of

cohort studies is that many different types of disease can be studied using the same cohort

Weakness: As in any kind of dietary investigation, to pack real scientific and statistical punch,

cohort studies also need to be extremely large and participants followed over a long period of time


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Case Control Studies/Retrospective studies

In a case control study, the research team works backward, from the effect to the suspected cause.

For this reason, case-control studies are often referred to as retrospective studies. Participants are

selected on the basis of the presence or absence of the disease or outcome in question, so there is

one group of people (case-subjects) with the health problem and one without (controls). These groups

are then compared to determine the presence of specific exposures or risk factors. An example of acase-control study would be to select a group of people with lung cancer and a group without and then

compare the two groups for their history of exposure to smoking.

Strengths: With enough subjects in the study and careful selection of controls, case-control

studies provide a cost-effective way to study disease

Weakness: Relies on memory, which is most of the times unreliable. In case-control studies, cases

and controls may remember their past diets differently.


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To sum up Epidemiological Research

1. They are observations of association, nothing more

4. The results do not prove a cause, but can suggest a

relationship between two factors

7. Using the results, they can design future research

studies

10.The results will be more revealing when combinedwith experimental research


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Experimental/Laboratory research

Basic research generates data by investigating biochemical substances or biological processes. It is often

conducted to confirm observations or to discover how a particular process works. For example, an

experiment might be conducted to examine how vitamin E helps prevent oxidation of LDL (low-density

lipoprotein) cholesterol, a process believed to play a role in the development of heart disease. These

studies can be done in two basic ways: In Vitroand In vivo

Invitro: Basic research is often conducted in vitro -- such as in test tubes -- or with animals. These

studies help researchers figure out precisely how and why certain foods or food substances might protect

against diseases.

Strengths: In vitro studies are tightly focused, which means that scientists can control for many

confounding variables. Once an in vitro study finds a suspect - a biological mechanism that might protect

against or add to your risk of disease they can then easily test their suspicions in an animal model.

Weakness: In vitro studies cant tell us if an anti-cancer effect that happens at the cell level also occurs in

the real world of the complex human body. They also cant tell us how much we might have to eat to reap

anti-cancer benefits, and they can only involve food components, not whole foods. You cant feed a cell an

apple.
http://www.aicr.org/site/PageServer?pagename=res_studies_invitroahttp://www.aicr.org/site/PageServer?pagename=res_studies_invitroa


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In vivo studies put diets to the test in complex living organisms. If cell or tissue studies ( in

vitro) provide evidence that nutrient X protects against disease, an in vivo study can give

researchers the next clue.

Strengths: Testing diets in animal models allows scientists much stricter control than with

humans. Unless they lock you in the lab, youre probably going to eat something that isforbidden, but a mouse eats what hes fed - so researchers know exactly whats going in and

whats going out

Weakness: Humans arent mice. While a surprising number of our biological processes may

be similar - especially the cancer process - many things that happen in mice dont happen

the same way in humans, and vice versa


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Controlled trials

This type of study uses human subjects to evaluate the effectiveness and safety of a nutrient or

medical treatment by monitoring its effect on large groups of people. Researchers affiliated with a

hospital or university medical program, independent researchers, or private industry generally

conduct the clinical trials that may be small, with a limited number of participants, or may be large

intervention trials that seek to discover the outcome of treatments on entire populations. The more

participants in the study, the greater the likelihood that the results can be replicated in the general

population.

Strengths: Controlled trials avoid many of the types of bias that can be found in other studies. They

also let scientists keep tight control over the enormous complexity of the study

Weakness: Its hard to blind people to dietary modifications.


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Randomised trial: In experimental research, study subjects (whether

human or animal) are selected according to relevant characteristics and

are then randomly assigned to either an experimental group or a control

group.

Double Blind Placebo trials: Considered the "gold standard" of

clinical research studies, the double-blind, placebo-controlled studyprovides dependable findings that are free of bias introduced by either

the subject or the researcher. In this type of study, neither the subject nor

the researcher conducting the study knows whether the test substance or

a placebo has been administered. For the results to be valid and to

ensure that the subject cannot violate the "blinding," the placebo and thetest substance must be virtually identical (i.e., look, smell, and taste

similar).


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Phases of clinical trial research

Phase I:Researchers test a new treatment or intervention in a small group of people forthe first time to evaluate its safety, determine a safe dosage range, and identify side effects

Phase II: The treatment is given to a larger group of people to see if it is effective and tofurther evaluate its safety

Phase III: The treatment is given to large groups of people to confirm its effectiveness,monitor side effects, compare it to commonly used treatments, and collect information that

will allow the drug or treatment to be used safely

Phase IV:Studies are done after the treatment has been marketed to gather information

about its effect in various populations and any side effects associated with long-term use.

Each phase is designed to answer a separate research question


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How to evaluate Research?

Ask the following questions, before jumping into conclusions

1.Has the study been published in a reputable scientific journal? This certainly lends the

finding more credibility

2.Who were the researchers? Were they hired by someone with a financial interest in

the study's results? This doesn't prove the findings were false, but it does bring them

into question.

3. What limitations were inherent in the type of study?

4. Who (or what) were the study subjects? Can the study's results be generalized to

other groups?

5. How do the results fit in with the body of research on the subject?

6. Has the author omitted important points in the background section of the study?

7. What size was the study group? Obviously, a study of several hundred people should

carry more weight than a study of five


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Communicating Risk

Absolute risk: is defined as the chance of a person developing a specific

disease over a specified time-period. For example, a woman's lifetimeabsolute risk of breast cancer is one in nine. That is to say, one woman in

every nine will develop breast cancer at some point in their lives

Relative risk: puts the chance in comparative terms by describing theoutcome rate for people exposed to the factor in question compared with the

outcome rate for those not exposed to the factor. For example, suppose that

a study shows that a man who brushes his teeth only once a day is 50

percent more likely to have all his teeth fall out in the next 10 years than

others who brush their teeth twice per day


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Tips for decoding Science Speak

May" does not mean "will". You really don't know the odds here

"Contributes to" and "is linked to" does not mean "causes". Other factors may be

more important.

Although scientific studies build on our current knowledge, one study taken alone

seldom proves anything. Subsequent studies may say exactly the opposite.

A "breakthrough" rarely occurs (example, the discovery of penicillin) but the term is

used too often.

"Double the risk" may or may not be meaningful. If your risk was 1 in 1,000,000 it

may now only be 1 in 500,000.

"Significant results" pop up all the time. A result is said to be statistically significant

when the association between the factors has been found to be greater than what

might occur at random. It may not mean "major" or "important".


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Understanding Studies