10/20/2005

Careers in Statistics

The Role of a Biostatistician

Presentation at Central College

Pella, Iowa

10/20/2005

What comes to mind when you hear the word “statistics”?

• Sports statistics?

• Vital health statistics?

• Just numbers?

10/20/2005

Leading causes of death in the U.S.Deaths Per Year (2001)

Percent of All Deaths

Heart Disease 696,947 29.0%Cancer 557,271 22.9%Stroke 162,672 6.8%

Chronic Respiratory Disease 124,816 5.1%Accidents (Unintentional) 106,742 4.2%

Diabetes 73,249 3.0%Influenza / Pneumonia 65,681 2.6%

10/20/2005

Cancer Death Rates*, for Men, US, 1930-2000

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Rate Per 100,000Lung

Stomach

Colon & rectum

Prostate

Pancreas

LiverLeukemia

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Cancer Death Rates*, for Women, US, 1930-2000

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UterusBreast Lung

Colon & rectumStomach

Ovary

Pancreas

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Tobacco Use in the US, 1900-2000

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Per capita cigarette consumption

Male lung cancer death rate

Female lung cancer death rate

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Trends in Overweight* Prevalence (%), Adults 18 and Older, US, 1992-2002

Less than 50% 50 to 55%

More than 55%

State did not participate in survey

*Body mass index of 25.0 kg/m2or greaterSource: Behavioral Risk Factor Surveillance System, CD-ROM (1984-1995, 1998) and Public Use Data Tape (2002), National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention, 1997, 2000, 2003.

1992 1995

1998 2002

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Discipline of Statistics

• The statistics presented here involve massive efforts to collect the data, followed by simple calculations.

• We see differences, but are they meaningful? Could they have happened by chance?

• If we see trends that we do not like, what can we do to effect change?

10/20/2005

Discipline of Statistics

• Numbers carry information, but we need numerical reasoning to make their meaning clear.

• The discipline of statistics uses mathematical tools to quantify uncertainty and assign a likelihood that what we see could have happened by chance.

• Biostatistics is just statistics applied in the health sciences.

• Mathematics and math logic play critical roles.

10/20/2005

Typical Research Questions

• We rely heavily on medications to treat diseases and medical conditions.– How do we know that they work (are

efficacious) and are safe?

• Heart disease is the #1 cause of death. – How can we assess if an intervention is

effective in reducing a person’s risk?

10/20/2005

Competing Possible Errors• Any research study has the possibility of making

one of two types of errors:

– Type I: Declaring a significant effect when in fact there is none.

– Type II: Failing to find a significant difference when there is one.

• In statistics, we use mathematical theory and modeling to find optimal decision rules and choose sample sizes which will reduce the likelihood of these errors to acceptable levels.

10/20/2005

Example: Clinical Trials

• One type of research design to address such questions is known as a clinical trial.

• In a clinical trial, patients are randomly assigned to either the new drug/treatment or “standard care”.

• When possible, both patients and doctors are blinded to the assignment.

10/20/2005

Clinical Trials

IHAST2 Trial

Intraoperative

Hypothermia for

Aneurysm Surgery Trial

Michael Todd MD, Bradley Hindman MD, Michael Todd MD, Bradley Hindman MD, William Clarke PhD, James Torner PhDWilliam Clarke PhD, James Torner PhD

University of IowaUniversity of Iowa and the IHAST2 Investigators.and the IHAST2 Investigators.

Supported by NIH RO1 NS38554Supported by NIH RO1 NS38554

10/20/2005

IHAST1• Hypothermia was first used in neurosurgery in 1955.

• Based on research experience with animals, it was believed that cooling the body before neurosurgery would be protective against central nervous system (CNS) insults.

• At present, at least 50% of current open neurovascular cases are cooled (Pemberton, 2003).

• However, this was being done without a rigorous assessment of outcomes.

10/20/2005

IHAST1• In 1999, U. of Iowa researchers published the results

of a small pilot clinical trial on this*.

• They randomly assigned 114 patients with and without acute aneurysmal subarachnoid hemorrhage (SAH) to either cooling or normal body temperature before surgery– Cooling = target body temperature of 33.5 C – Normal = body temperature 37C

Hindman, Todd, et al. Neurosurgery. 1999 Jan;44(1):23-32; discussion 32-3.

10/20/2005

IHAST1

71

57

0102030405060708090

100

Goo

d

Mod

erat

e

Sever

e

Veget

ativ

eDea

d

SAH (n = 52)

Hypothermia, n=24

Normothermia, n=28

Outcome = Glasgow Outcome Score at Three Months

7776

0102030405060708090

100

Good

Mod

erat

e

Sever

e

Veget

ative

Dead

No SAH (n=62)

Hypothermia, n=30

Normothermia, n=29

10/20/2005

IHAST1• Is it beyond reasonable doubt that hypothermia

is working?

• SAH patients (n=52) : 71% vs. 57% =“good” – Looks like hypothermia is helping.

• No SAH (n=62): 77% vs. 76% = “good”– Looks like little effect of hypothermia.

10/20/2005

IHAST1• Answer:

No - there is reasonable doubt.

• Statistical methods were used to determine(1) These differences, given this sample size, could

have reasonably occurred by chance .

(2) It would need a randomized clinical trial of at least 900 patients to assure that we could detect a 10% improvement (from 65% to 75%) in the Glasgow outcome score at three months with 90% power.

10/20/2005

IHAST2• The follow-up International, multi-center

randomized clinical trial was funded by NIH (IHAST2).

• 1000 SAH patients undergoing craniotomies for aneurysm clipping were randomized to either hypothermia or normal body temperature.

• Primary outcome measure: Glasgow Outcome Score (GOS) at 3 months

10/20/2005

IHAST2: Glasgow outcome score66

63

21 22

7 9.4

0.2 05.8 6.4

0

10

20

30

40

50

60

70

Good ModerateDisability

SevereDisability

Vegetative Dead

Hypothermia, n=499

Normothermia, n=501

The previous 71%-57% difference has now shrunk to a 66%-63% difference

10/20/2005

IHAST2Now, is it beyond reasonable doubt that

hypothermia is working?

• This study had a large enough sample size to find a meaningful difference in “good” outcomes due to hypothermia (should it work) with high probability.*

Beyond reasonable doubt, it simply does not work as believed.

* Many other outcomes were also tested. All consistently showed no benefit.

10/20/2005

Missouri Turkey Hunting Survey

• The Missouri Department of Conservation is interested in turkey hunting success rates.

• Can we obtain an estimate of the hunting success rate in every county on every day of the hunting season even if we don’t have a sample from that county?(small area estimation)

10/20/2005

Missouri Turkey Hunting Survey

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Missouri Turkey Hunting Survey| ( , ) ~ ( , )

log1

represents the effect of county

represents the effect of day j

represents random residuals

ij ij ij ij ij

ijij i j ij

ij

i

j

ij

y n p Binomial n p

pu Z e

p

Z i

e

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Missouri Turkey Hunting Survey

0111

1001

1001

1110

C

I

mmimimi ZCNZZ

1

,~|

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Missouri Turkey Hunting Survey

1

is a measure of correlation

is random error

t t t

t

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What do statisticians do?• Surveys

– political surveys– National Health and Nutrition Examination Survey

• Government Operations– Census Bureau– FDA

• Scientific Research– Cancer trends– Survival probability– Genetics

• Business and Industry– Pharmaceuticals

Source: http://www.amstat.org

10/20/2005

EnvironmentAgriculture,

Ecology, Forestry,Animal Populations

GovernmentCensus, Law,

National Defense

PhysicalSciences

Astronomy,Chemistry, Physics

Areas where STATISTICS

are used

Health & Medicine

Genetics, Clinical Trials,Epidemiology,Pharmacology

BusinessEconomics, Engineering,

Marketing,Computer Science

Source: http://www.amstat.org

10/20/2005

Roles of a Biostatistician• Guardian of the science.

– Help write the proposal to get this study funded.

– Maintain an unbiased perspective.

– Determine which data needed to be collected.

– Determine what methods would be used.

– Anticipate how proposed changes in the program would affect ability to make inferences and argue against them when needed.

– Develop new methods when needed.

10/20/2005

• Keeper of the Data.• Work with different state and federal agencies to obtain

data.

• Check data for recognizable errors.

• Merge data from different sources.

• Maintain and secure the project database.

• Work with others (e.g., national evaluators, statistical coordinating centers) to blend your data with other data.

Roles of a Biostatistician

10/20/2005

• Analytic Support• Investigate the data from many angles.

• Assess assumptions of proposed models.

• Fit statistical models.

• Interpret results of the models for the research team.

• Make sure that the investigators do not draw conclusions beyond what can be supported by the data.

• Author (Write up results / provide graphics.)

Roles of a Biostatistician

10/20/2005

What About Salaries?

• Annual (median) salary with 0-1.9 years of experience for

Masters PhD

- Statistician 60,000 83,000

- Male Statistician 56,500 83,000

- Female Statistician 62,000 83,000

- Assistant Professor (4 year college) 53,000

- Assistant Professor (Research) 63,000

- Pharmaceutical statistician 73,000 83,000

Source: http://www.amstat.org

10/20/2005

Life as a Graduate Student

• What do you do as a graduate student?– Classwork– Teaching assistants– Research assistants– Go to football games!

10/20/2005

Variety of scientific projects

As you can tell, people work on various different projects. The following are brief excerpts from some recent projects.

10/20/2005

Driving Simulator (NADS)

http://www.nads-sc.uiowa.edu/

A shared-use research facility operated by The University of Iowa, The NADS was created to conduct research which will help save lives, reduce the costs of vehicle crashes, and lead to better and safer vehicles, roadways, and drivers.

10/20/2005

Iowa Cochlear Implant Center

While normal hearing has increased significantly, implants still do not reproduce a high quality of music.

Is it beneficial to have two cochlear implants for those who are profoundly deaf?

CNC Words

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10/20/2005

Iowa Bridge to Employment Study• Purpose: To determine if special services provided to Iowans

with disabilities would increase the likelihood of employment.Mental Retardation GroupMental Illness Group

10/20/2005

Wise Woman

10/20/2005

Percent of Iowans Age 65 and Older

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0.05

0.1

0.15

0.2

0.25

1970 1975 1980 1985 1990 1995 2000

Year

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cen

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< 10,000

10,000 - 20,000

> 20,000

MSA

State of Iowa

http://www.public-health.uiowa.edu/FACTBOOK

Cancer Crude Rates

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Year

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> 20,000

MSA

State of Iowa

Total Physicians

10/20/2005

Holden Comprehensive Cancer Center

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(cm

3 )ControlVaccineGITR+Vaccine

Tumor growth curve estimates from a mixed linear models analysis.

Groups n Mean Tumor Size (cm3) p-value Group Comparisons

Control (1) 17 1390.2

0.0006 (1, 23)Vaccine (2) 35 692.0

GITR + Vaccine (3)

38 444.0

Group comparisons indicate differences between specific groups at the 5% level of significance.

10/20/2005

Radon concentrations measured in the basements of homes in Iowa.

Spatial statistics

10/20/2005

Thank you!

Jake OlesonCentral Collegeclass of 1997