Epidemiology and Biostatistics

HIM 3200Session One

Dr. Burton

Course DescriptionThe goals and objectives of epidemiology, its

policy and procedure, and its foundation and support in health care information are the focus of this course. Investigation of an epidemic, measures of mortality, incidence and prevalence, measures of risk, biological variability, probability, screening, sampling, statistical significance, correlation, multiple regression, retrospective and prospective studies, and survival analysis are discussed. Advanced techniques for the statistical analysis of institutional case-mix and quality improvement data are presented.

Course ObjectivesStudents will be able to demonstrate through written

assignments and testing the following:

1. Retrieve patient data from departmental databases.2. Compute routine institutional statistics. 3. Design data tools for research studies to evaluate

patient outcomes.4. Assist in interpretation of data.5. Prepare data for presentation.6. Present data.Perform statistical analysis.7. Design reports using database report generation.8. Design department systems for analysis of patient

data.

Measuring Student Progress

1.      Chapter Exercises & Review Questions 200 (20 points each)2.      Progressive Mastery Exam 250

(Best Score of the three takes)3.      Midterm Exam 2504.      Epidemiologic Analysis 250 Written report (100)

Group Presentation (100) Peer Evaluation (50)5. Final Exam 50

TOTAL 1000

CHAPTER 1

Statistics and How They Are Used

OUTLINE  1.1    The Meaning of Statistics

Formally defines the term statistics and illustrates by describing what a statistic does1.2               

The uses of statisticsShows how descriptive statistics are used to describe data and how inferential statistics are used to reach conclusions from the analysis of data.

1.3                Why study statistics?Explains how the study of statistics is important for research, for writing publishable reports, for understanding scientific journals, and for discriminating between appropriate and inappropriate uses of statistics.

1.4                Sources of DataDiscusses surveys and experiments, two main sources of data, and further classifies surveys as retrospective or prospective and as descriptive or analytical.

1.5                Clinical TrialsDescribes the use of a clinical trial to determine the value of a new drug procedure.

1.6                Planning of SurveysPreviews some hints on how to maximize the value of survey data.

1.7                How to Succeed in StatisticsOffers some tips on getting the most out of class and other resources.

 

LEARNING OBJECTIVES • 1.                   Define statistics

• 2.                   List several reasons for studying statistics

• 3.                   Distinguish clearly between– a.                    descriptive and inferential statistics– b.                   surveys and experiments– c.                    retrospective and prospective studies– d.                   descriptive and analytical surveys

• 4.                   Define bias

• 5.                   Describe the purpose and components of a clinical trial

THE MEANING OF STATISTICS • A.                 What Does Statistics Mean?

– 1.                    Refers to a recorded number

– 2.                    Denotes characteristics calculated for a set of data• a.                   Standard deviation• b.                   Correlation coefficient

– 3.                    A body of techniques and procedures dealing with the collection, organization, analysis, interpretation, and presentation of information that can be stated numerically

• B.                  What Do Statisticians Do?– 1.                    Works on challenging scientific tasks

– 2.                    Primarily concerned with developing and applying methods that can be used in collecting and analyzing data

– 3.                    Tasks are as follows• a.                    To guide the design of an experiment or survey• b.                   To analyze data• c.                    To present and interpret results

 

THE USES OF STATISTICS

A.                 Descriptive Statistics – deals with the enumeration, organization, and graphical representation of data 

Example: Census

 B.                 Inferential Statistics – concerned with reaching conclusions from incomplete information – generalizing from the specific 

Example: Opinion Poll (Gallup Poll) 

C.                  Statistical methods provide a logical basis for making decisions in a variety of areas when incomplete information is available

WHY STUDY STATISTICS?

A.  Essential for both understanding and conducting research

B.  Used to analyze data

C.  Can help to discriminate between fact and fiction

D.  Helpful in knowing when, and for what purpose, a statistician should be consulted

SOURCES OF DATA

A.  Surveys

B.  Experiments

C.  Retrospective Studies (case-control studies)1.  Disadvantage – usually collected for other purposes

and may be incomplete2.  Advantages

a. economicalb. answers usually obtained relatively quickly

SOURCES OF DATA

D. Prospective Studies (cohort studies)

1. Advantages

a.  collect relevant data

b.  collect data under uniform conditions and for specific reasons

c.  better opportunities to draw appropriate conclusions or make appropriate comparisons while limiting or controlling the amount of bias

2.  Disadvantage – typically not used to establish or “prove” a causal relationship because variables cannot be randomly assigned or manipulated

SOURCES OF DATA

E.   Comparison of Ratios

F.   Descriptive Surveys – provide estimates of a populations characteristics

G.  Analytical Surveys – Seek to determine the degree of association between a variable and a factor in the population

CLINICAL TRIALS

A. Definition: a carefully designed experiment that is generally considered to be the best method for evaluating the effectiveness of a new drug or treatment

B.  Protocol1. Describes in detail the design of proposed research

2.  Clearly defined hypothesis

3.  Detailed delineation of inclusion and exclusion criteria for study subjects

4.  Descriptions of the proposed interventions and the randomization process

5.  Detailed explanation of how bias may be minimized

6. Description of the procedures to minimize errors in the collection and analysis of data

CLINICAL TRIALS

C.   Two key features

1.  Blinding – study subjects and/or the investigators do not know who is in the control group and who is in the experimental group with the purpose of reducing bias

2. Randomization – subjects are randomly assigned to either the experimental or control group

Standard 2 X 2 table

a = subjects with both the risk factor and the diseaseb = subjects with the risk factor but not the diseasec = subjects with the disease but not the risk factord = subjects with neither the risk factor nor the diseasea + b = all subjects with the risk factorc + d = all subjects without the risk factora + c = all subjects with the diseaseb + d = all subjects without the diseasea + b + c + d = all study subjects

Present Absent

Present

Absent

Disease status

Risk FactorStatus

aa bb

cc dd

a + ba + b

c + dc + d

a + ca + c b + db + d a+b+c+da+b+c+dTotal

Total

PLANNING SURVEYS

• A.                 Formulate a clear plan of action before starting a survey

• B.                  Outline major steps to be followed

HOW TO SUCCEED IN STATISTICS

• A.                 Scan the chapter outline

• B.                  Read the conclusion and vocabulary list

• C.                  Review the learning objectives before coming to class

• D.                  After class learn relevant terms, concepts, principles, and formulas

• E.                   After doing the assigned exercises, try to reformulate the objectives as questions and then answer them

• F.                   Read essays dealing with the application of statistics to a variety of fields

CONCLUSION

A statistician designs efficient and unbiased investigations that provide data that he or she then analyzes, interprets, and presents to others so that decisions can be made. To do this work the statistician uses techniques that are

collectively called “statistics.”

HAS 3200Intro to Epidemiology

Session One

Dr. Burton

What is epidemiology?

The scientific study and understanding of disease.

Webster: “a branch of medical science that deals with the incidence, distribution and control of diseases in a population.”

Dictionary of Epidemiology: “the study of the distribution and determinants of health-related states or events in specified populations, and the application of this study to the control of health problems.” (Last, 1995)

Factors involved in the natural history of disease

Agent

Vector

Host Environment

HostHost

HostHostThe human body

“Susceptible individual”

Carriers:Active (infected)Incubatory (early stages)Convalescent (recovering)Intermittent (Occasional transmission)

“Web of Causation”

“A number of interrelated causes…and… the relationship is not necessarily a simple, linear, cause-effect progression.”

Agents

Biologic

Chemical

Physical

Social & psychological stressors

Sometimes called pathogens:Characterized by

Virulence (strength)Invasiveness (ability to enter the host)Communicability (ease of the agent’s

spread from one host to the next)

Vectors

Insects (mosquitos)

Arthropods(ticks)

Animals

Other terminology

• Fomites: inanimate objects within the environment such as soiled linen or doorknobs.

• Common vehicle: water or tainted food.

• Serial transfer: STDs from one host to the next.

Environment

Weather

Social

PoliticalEconomic

Reservoirs

Factors

• Host (Individual susceptible) • Agent

– Biologic– Chemical– Physical– Social & psychological stressors

• Vectors– Transmitter (animal, insect, humans,

objects)

• Environment

Definitions

• Epidemic:– An acute outbreak of disease that

reaches levels greater than normal.

• Pandemic:– Global or widespread outbreaks.

• Endemic:– Higher normal levels of disease in

certain populations

BEINGS ModelPreventable causes of disease

BBiologic factors and Behavioral factors

EEnvironmental factors

IImmunologic factors

NNutritional factors

GGenetic factors

SServices, Social factors, and Spiritual factors

Behavioral Factors

• Life Style:– High risk behaviors

Repeat after me:

I will never complain about MY kids again ...

I will never complain about MY kids again ...

I will never complain about MY kids again ...

I will never complain about MY kids again ...

I will never complain about MY kids again ...

Environmental Factors

Immunologic Factors

Herd ImmunityBy immunizing

members of the “herd” the chain of transmission to unimmunized members is disrupted.

Nutritional factors

Denis Burkitt:1. “By world standards, the entire US is

constipated.”2. “Don’t diagnose appendicitis in Africa

unless the patient speaks English.”3. “African medical students go through 5

years of training without seeing coronary heart disease or appendicitis.”

4. “Populations with large stools have small hospitals. Those with small stools have large hospitals.”

Diseases Rare in indigenous Africans:

AppendicitisBreast cancerColon cancerCoronary heart diseaseDiabetes mellitusDiverticulitisGallstonesHemorrhoidsHiatal herniaVericose viens

Genetic Factors

“ …population gene frequencies appear to be stable.”

Services, Social Factors, and Spiritual Factors

Medical Services“Iatrogenic illness and injury”

Social Factors “Support”FamilyFriendsNetworksMemberships

Spiritual

Causal Research

• Two fundamental distinctions– Those who do not have the risk factor

(independent variable)– Those who do have the risk factor (dependent

variable)

• Measurement of contrast– Cohort studies

• Persons exposed to a risk factor• Persons not exposed to a risk factor

– Case-control studies• Case subjects• Control subjects