Clinical/Medical Research Designs David M. Fresco, Ph.D. Professor Department of Psychological Sciences Kent State University Kent, Ohio, USA

A healthy lifestyle may be the key to a long life

Do Tibetans have a natural immunity to life style diseases? For many years, Tibetans appeared to have an immunity to lifestyle diseases such as high blood pressure Diet? Exercise? Adaptation to living at high altitude? Since the Tibetan Diaspora to India, incidence of lifestyle diseases on the rise among ethnic Tibetans There appears to be relatively less awareness and knowledge about these controllable conditions

Outline of this lecture Using “lifestyle” diseases as an organizing principle: Illustrating important research methodologies commonly used in by Western scientists that might shed light on the effects of lifestyle diseases After, engage in a small group exercise to design methodologically sound studies to explore and interrogate the problems associated with lifestyle diseases among ethnic Tibetans within and outside of Tibet

The Scientific Method Science is the pursuit of systematized knowledge through observation Objectives description prediction control understanding

Study Designs From http://www.cebm.net/index.aspx?o=1039 Doesn’t include before and after studies descriptive studies case report, case series, qualitative study, cross sectional survey show what’s happening in a population and in subgroups analytic studies examine effect of intervention (I)/exposure (E) on outcome (O) compare frequency of outcomes in a comparison (C) group with frequency in intervention or exposed group to quantify effect may be experimental or observational Centre for Evidence Based Medicine, Oxford, UK cebm.net Prospective A prospective study watches for outcomes, such as the development of a disease, during the study period and relates this to other factors such as suspected risk or protection factor(s). The study usually involves taking a cohort of subjects and watching them over a long period. The outcome of interest should be common; otherwise, the number of outcomes observed will be too small to be statistically meaningful (indistinguishable from those that may have arisen by chance). All efforts should be made to avoid sources of bias such as the loss of individuals to follow up during the study. Prospective studies usually have fewer potential sources of bias and confounding than retrospective studies.   Retrospective A retrospective study looks backwards and examines exposures to suspected risk or protection factors in relation to an outcome that is established at the start of the study. Many valuable case-control studies, such as Lane and Claypon's 1926 investigation of risk factors for breast cancer, were retrospective investigations. Most sources of error due to confounding and bias are more common in retrospective studies than in prospective studies. For this reason, retrospective investigations are often criticised. If the outcome of interest is uncommon, however, the size of prospective investigation required to estimate relative risk is often too large to be feasible. In retrospective studies the odds ratio provides an estimate of relative risk. You should take special care to avoid sources of bias and confounding in retrospective studies.  http://www.statsdirect.com/help/basics/prospective.htm

The Correlational Method The correlational method examines the relationship between or among two or more variables The variables are assessed as they exist in nature (no experimental manipulation) Correlational studies seek to determine the magnitude and direction of a relationship among variables e.g. stress and body weight

How to Read a Correlation Coefficient

Observe or Conduct Experiment? Observational cross sectional, case series, case-control studies, cohort studies identify participants observe and record characteristics look for associations Experimental before and after studies, comparative trials, (controlled or head to head), randomized trials place in common context intervene observe/evaluate effects of intervention experimental study researcher manipulates exposure by allocating participants to intervention or exposure group follow up under carefully controlled conditions. Controlled trials, when randomised and blinded, can control for biases analytic observational study case control, cohort, some cross-sectional studies measure exposure in the groups match groups of participants assess associations between exposures and outcomes Centre for Evidence Based Medicine, Oxford, UK cebm.net

The Survey Method Used in both descriptive and correlational research Survey technique asks questions of large numbers of persons to gain information on attitudes and behavior Two main approaches Questionnaires Interviews Interview, mail, phone, internet, etc.

The Survey Method Pros: Good, cheap, anonymous, diverse population, Easy to get random sampling (a sampling that represents your population you want to study) Cons: Low Response Rate Sampling issues People may not respond accurately People Lie or just misinterpret themselves Wording Effects

Random Sampling

The Cross-sectional Method Snap shot Measure exposure and outcome variables at one point in time Main outcome measure is prevalence at this point in time NB Prevalence versus incidence (get over time) Relative prevalence - prev in group with RF compared to those without,

Cross-sectional Study What is the current prevalence of lifestyle diseases among ethnic Tibetans? Image from http://www.fsrrn.net/modules/content/

Cross-sectional Study: Strengths Generalizable results if sample reflects the whole population Can study multiple outcomes and exposures Immediate outcome assessment and no loss to follow-up, therefore faster, cheaper, easier Can measure prevalence Hypothesis generating for causal links Serial surveys to avoid learning effect from baseline measurement with cohort study

Cross-sectional Study: Weaknesses Provides limited information Cannot establish sequence of events establishes association at most, not causality Impractical for rare diseases Prone to bias recall bias social desirability bias Serial surveys to avoid learning effect from baseline measurement with cohort study

Variation on Cross-sectional design with Prospective Assessment Image from http://www.fsrrn.net/modules/content/ Time Present (Red = risk factor present) Future (Red = develops disease)

The Experiment The experiment allows for determination of a causal relation between two or more variables An experiment involves random assignment of subject to experimental conditions manipulation of an independent variable (IV: believed to be a causal variable) measurement of a dependent variable (DV is assumed to the controlled by the IV)

Experimental Study Vocabulary Independent Variable (IV) Factor that is manipulated Dependent Variable (DV) Factor that is measured Extraneous Variables Factors that effect DV, that are not IV Experimental Group Group exposed to IV Control Group Group not exposed to IV Placebo Inert substance that is in place of IV in Control Group

Randomized Controlled Trial (RCT) True experimental design Participants assigned by chance, following consent, to one of at least two conditions Key features of classic experimental design: Random assignment determines who assigned to which group Pre & post tests outcome measured before & after intervention Control group same experiences as experimental group except no exposure to experimental stimulus

Randomized Controlled Trial (RCT) Study designs Centre for Evidence Based Medicine, Oxford http://www.cebm.net/index.aspx?o=1039

Randomized Controlled Trial (RCT) Study designs Centre for Evidence Based Medicine, Oxford http://www.cebm.net/index.aspx?o=1039

Pros and Cons of RCT Advantages Can establish causal relationship between IV and DV Unbiased distribution of extraneous variables Randomization facilitates statistical analysis Disadvantages Expensive: time and money Volunteer bias Ethically problematic at times Study designs Centre for Evidence Based Medicine, Oxford http://www.cebm.net/index.aspx?o=1039

Your Assignment

Your Group Assignment Using the materials provided, design four studies that will help us understand the impact of lifestyle diseases on ethnic Tibetans living in India Survey study Cross-sectional study Prospective study RCT

Survey Study Main Question: What is the current prevalence of lifestyle diseases among ALL ethnic groups in India? Secondary Question: How much knowledge of life style diseases do residents of India possess? Assignment Design a survey study to address these questions Give consideration to sampling (e.g., random vs. volunteers) Give consideration to recruitment strategies and formats for completing assessments

Cross-sectional Study Main Question: What is the association of lifestyle risk factors (e.g., diet, exercise, smoking, etc.) to current prevalence of lifestyle diseases among ethnic Tibetans in India? Secondary Question: Is knowledge of lifestyle diseases associated with lower rates of actual lifestyle diseases once they are formally assessed? Assignment Design a cross-sectional study to address these questions Give consideration to recruitment strategies and formats for completing assessments

Prospective Study Main Question: Among ethnic Tibetans, what is the association of current lifestyle risk factors (e.g., diet, exercise, smoking, etc.) and protective factors (e.g., knowledge of lifestyle diseases) on the likelihood of developing lifestyle disease in the future Assignment Design a prospective study to address these questions Give consideration to recruitment strategies and formats for completing assessments Hint: Consider creating subgroups (e.g., high risk/low knowledge, high risk/high knowledge, etc.)

RCT Study Main Question: Can a program of diet and exercise help reverse or control the effects of lifestyle diseases among ethnic Tibetans who have or are at risk for lifestyle diseases? Secondary Question: Drawing on your knowledge of Tibetan and Indian culture, what are the challenges in persuading participants to remain adherent to the diet and exercise regimen? Assignment Design a RCT to address these questions (e.g., Treatment vs. Control or Treatment versus Placebo, etc.) Give consideration to recruitment strategies and formats for completing assessments Give consideration to describing ways to tailor a program consisting of diet and exercise to make the program maximally appealing to ethnic Tibetans