Annual Arizona Conference for Tribal BCCEDP Collaboration, Flagstaff, AZ

Inter Tribal Council of Arizona, Inc.
Tribal Epidemiology Center
TEC Director
Jamie Ritchey, MPH, PhD
August 7, 2012

Objectives

• Overview of Inter Tribal Council of
Arizona (ITCA), Inc. Tribal Epidemiology
Center (TEC)

• Epidemiology Basics

• Practical Applications of Epidemiology

Overview of Inter Tribal
Council of Arizona, Inc. (ITCA)
Tribal Epidemiology Center (TEC)


• Who we are

• Where we are

• What services are provided

• How to request services and partnerships

ITCA, Inc. Regional Epidemiology Center:
• Established in 1996

• Mission: Empowering the American Indian Tribes in
Arizona, Nevada, and Utah in the further development
of health services and systems

• Purpose: To support Tribally-driven Health Surveillance
Systems that can assess both individual and community
health status, facilitate planning, and manage existing
health services

• Services
– Community health profile (CHP) assistance
– Epidemiology and other public health trainings
– Study and survey design
– Data collection and analysis
– Technical report creation and review
– Educational materials for health-related topics
– Coordination of services during outbreaks or disease
cluster investigations
– CHP and Community Health Accreditation (CHA) tool kits
for Tribes coming soon!

• How can I request ITCA, Inc. TEC services?
– E-mail ITCA, Inc. TEC for assistance directly at:
TECinfo@itcaonline.com

– TEC staff will respond within 48 hours and provide you with a fillable
form to complete

– TEC staff will meet with you by phone or e-mail to discuss a project
work plan

– TEC staff will decide with you the format and delivery method of the
final product1
1Please allow at least 2 weeks for project completion, possibly longer depending on the
scope of the project

Epidemiology Basics

• Epidemiology
– Definition
– How public health professionals use it
• Types of Epidemiology
• Descriptive Epidemiology
– Person, place, time
– Measures
– Relationship between measures

Epidemiology Basics
Epidemiology is defined as:

“…the study of the distribution and determinants
of health-related states or events in specified
populations and the application of this study to
control of health problems.”1

1 Gordis, L. Modern Epidemiology 2nd Edition. 2000. W.B. Saunders Company, Philadelphia.
ISBN 0-7216-8338-X

Epidemiology Basics
• It enables public health professionals
to:
– Understand the local disease patterns
– Identify populations at risk for disease
– Establish associations with risk factors and
disease
– Determine causes of disease
– Develop new prevention programs and
policies
– Set health-based standards

Epidemiology Basics
• Descriptive epidemiology1
– Person, place, time
– Measures: counts, proportions, rates
– Explains or quantifies a particular disease or problem
(ex. Cancer rates)
• Analytic epidemiology
– Tests a hypothesis
– Measures: relative risk, odds ratios
– Describes associations between a risk factor and a
disease (ex. Smoking and lung cancer relationship)

1Focus for today’s talk

Epidemiology Basics
• Person
– Ex. Diagnosed
Colorectal cancer
cases

• Place
– Arizona
Community Health
Analysis Areas

• Time
– 1995-2000
– 2001-2004

Epidemiology Basics
• Uses statistical measures to describe:

– New cases of disease and death

– People living with disease

– Identify possible risk factors for the disease

Epidemiology Basics

• Counts / Frequency
The number of events (“cases”) that occur
in a population of interest
– Example: There were 87 cancer cases in
Tribe A
• Is this story complete?
• What else would you like to know?

Epidemiology Basics

• Proportions give a magnitude to events
• Useful info might include:
– Time
• 87 cancer cases in 1 year (1999)
– Total Number of Deaths
• 87 cancer deaths/1,000 total deaths = 0.087
• Multiply by 100%  0.087 x 100% =
8.7% of deaths were cancer cases in 1999

Epidemiology Basics

Types of Rates
• Crude rates
• Stratified or Specific Rates
– Better detail
– Uses specific population (age group, sex,
ethnic group, etc.)
– Ex. Cancer death rates in males & females
• Adjusted rates
– age

Epidemiology Basics

• Proportions
– Prevalence (NOT a rate)
– Not directly comparable across groups
– Used for public health planning purposes to
determine the burden of disease
• Rates
– Incidence and Mortality rates
– Allow health comparisons within and between groups

Epidemiology Basics
• Incidence rate: Risk of
disease development in
the population (new
cases)

• Prevalence: Fraction of
population with illness in
population

• Mortality rate: Risk of
Death

• Incidence and prevalence
are related:
I X P = Duration

Epidemiology Basics
• How do epidemiologists know when rates
are statistically different?
There are measures that can determine if
differences are statistically significant…
– P-values of p<0.05 indicate that measures have a statistically
significant difference

– 95% Confidence intervals that do not overlap are considered a
way to tell if measures show a statistically significant
difference. These intervals can also tell us about the
magnitude of the difference.

Epidemiology Basics

Statistical measures are used to tell a
story…but where do I get data to tell it?

Practical Applications
of Epidemiology

Practical Applications of
Epidemiology

• Arizona Cancer Registry

• Statistics for working documents
– Scenarios

Arizona Cancer Registry
• Began in 1981

• Mandatory cancer reporting in
1988 Arizona Revised Statute §36-133

• Rules for case reporting in 1992
Arizona Administrative Code Title 9,
Chapter 4

• Provide data to New Mexico
Tumor Registry for American
Indian registry for SEER
statistics

• Population-based NPCR registry:
Arizona Cancer Registry Home page:
– Cancer site
http://www.azdhs.gov/phs/phstats/acr/
– Case demographics
– Year of cancer diagnosis

Arizona Cancer Registry

What statistical measures are available?
• Cancer case counts
• Cancer incidence rates1
• Cancer mortality rates2
• Population estimates
– Denominator data

1Age-adjusted incidence rates; 2Crude mortality rates per 100,000

Statistics for working
documents
Scenario 1. A Tribal community cancer researcher has heard rumors
from concerned community members that there may be a high risk of
colorectal cancer in her area. From her training, she remembers that
the national trend of age-adjusted incidence rate of colorectal
cancers from 1992-2009 were dropping in the US1. She wants to
determine if her community has a high risk of colorectal cancer
compared to others.

• What are the person, place, and time components?
• What measure is needed to determine risk and can be directly
compared across geographical areas?
• How can I get this information from the Arizona cancer registry?

1 Age-adjusted colorectal cancer incidence rate trend slides from SEER are included in the presentation.

documents
What data does the researcher need?

• Person
– Colorectal cancer cases among AZ residents and Tribal
community members

• Place
– Arizona state in community health analysis areas (CHAAs)1

• Time
– Not specified
– Data lag, limited to what is available2
1Tribespecific data is not publicly available. Community Health Analysis Areas are used to estimate
Incidence rates based on Census blocks in Tribal areas and may include non-Tribal members.
2Cancer data takes at least 18 months to check for completeness from the central registry.
http://azdhs.gov/phs/azchaa/CHAA_FAQ.pdf

documents
What statistics do we use to determine the
risk of colorectal cancer comparing areas?

Use age-adjusted incidence rates:
• Risk of getting disease
• Comparisons of groups

Use 95% confidence intervals:
• Rate differences are statistically significant
• Magnitude of the difference
• Stability of the rates1

1Rates may be unreliable with small numbers of cases. The 95% CIs will often be a wide range.

documents

documents
Three ways to get the
state data:
• From the home page, go
to the Cancer Data Query
System link

• Contact the Arizona
Cancer Registry Data
Section by e-mail or
phone

• Request services from http://www.azdhs.gov/phs/phstats/acr/
TEC

documents
The Cancer Data
Query System,
incidence rates can be
access in two ways:
– Age-adjusted cancer
Incidence rates

– ACR Community
Health Analysis Area
Maps1

documents
Incidence rates and 95%
Confidence Intervals:

– For AZ
– By Year
– All race/ethnicity
– AI/ANs

documents
AZ colorectal cancer age-adjusted
incidence rates show a decreasing
trend from 1995-2009 for both males
and females1

• The age-adjusted incidence rate of
colorectal cancer in 1995 for AZ
men was 57.8 per 100,000 (95% CI:
54.2-61.4) and in 2009 was 40.9
(95% CI: 38.4-43.4) 2

colorectal cancer in 1995 for AZ
women was 38.1 per 100,000 (95%
CI: 35.2-40.9) and in 2009 was 31.8
(95% CI: 29.6-33.9) 2

1 Results from a trend test would tell us if this downward trend is statistically significant
2 Statistically significant difference.

documents
AIs in AZ1:
colorectal cancer in 1995 for AI
men was 50.6 per 100,000 (95% CI:
34.9-66.4) and in 2009 was 32.2
(95% CI: 21.8-42.5). In 2005, the
rate was 41.0 (95% CI: 28.8-53.3).

colorectal cancer in 1995 for AI
women was 9.7 per 100,000 (95%
CI: 3.1-16.3) and in 2009 was 18.4
(95% CI: 10.8-25.9). In 2006, the
rate was 30.5 (20.4-40.5).2

1 Results from a trend test would tell us if this downward trend is statistically significant
2 Statistically significant difference comparing 1995 and 2006 for women.

documents
The Cancer Data Query
System, incidence rates
can be access in two
ways:
Incidence rates

– ACR Community
Health Analysis Area
Maps1

documents
• What is an Arizona Community health analysis
area (CHAA)?
CHAA basics:
– NOT Tribal specific data
– Built on the 2000 Census Block groups
– Contain a range of 5,000-190,000 residents
– Cancer cases are assigned based on place of residence
– PO boxes were assigned to the town of the zip code
– About 2% of cancer cases did not get assigned to CHAA
– Additional information on CHAA:
http://www.azdhs.gov/phs/azchaa/CHAA_FAQ.pdf

documents
• Choose the cancer site and years

documents
• Select colorectal cancers and either
2001-2004 or 1995-2000

documents
• Apply the filter for Indian community „yes/no‟

documents
• 14 CHAA areas had fewer than 10 colorectal cases
• Some CHAA incidence rates appear higher than others
• Navajo Nation CHAA had the highest amount of cases in any CHAA
(n=40) (But not the highest incidence rate!)

documents
CHAA age-adjusted incidence rates
for colorectal cancer from 2001-
20041:
• The 95% CIs indicate that the rates
for Yavapai-Prescott CHAA 282 per
100,000 (95% CI: 0 – 835), Cocopah
CHAA 86.0 (95% CI: 0-254.8) and
other CHAAs with a small number
of cases are unstable2

• The Navajo Nation CHAA has a
stable rate of 13.7 (95% CI: 9.4-
18.0)

1 Limited to Indian Community in CHAAs.
• The Fort Mohave [Mojave] CHAA
2 TECs are formalizing a small numbers protocol. Many
rate of 39.4 (95% CI: 20.8-57.4) and Agencies do not report rates based on fewer than 20 cases.
Salt River CHAA rate of 77.1 (95%
CI: 40.9-113.3), these CHAAs are
fairly stable2

documents
What is the researcher‟s story that describes colorectal cancer?
• National and AZ age-adjusted incidence rates for colorectal cancer are decreasing, but
getting screened for colorectal cancer on an individual level is still VERY important

• Among AIs in AZ, age-adjusted incidence rates may have decreased for AI men and may have
increased for AI women from 1995 to 2009, but data is limited

• Navajo Nation CHAA had the highest case count of colorectal cancer (n=40) from 2001-2004

• The age-adjusted incidence rate of 13.7 (95% CI: 9.4-18.0) for colorectal cancers in the
Navajo Nation CHAA is lower than the state and national rates

• The Navajo Nation CHAA age-adjusted incidence rate is lower than Fort Mohave [Mojave]
CHAA 39.4 (95% CI: 20.8-57.4) and Salt River CHAA 77.1 (95% CI: 40.9-113.3) per 100,000.
These differences are statistically significant.

• Other CHAA areas had higher reported rates, but these rates are unstable due to small
numbers of cases

documents
Scenario 2. A multi-disciplinary team of Tribal cancer researchers want to
propose a case control study with several community members in order to
investigating the relationship between esophageal cancer and arsenic in
the drinking water among AI/AN populations in Arizona from 1995-2004.
Writing the project proposal introduction, the researchers want to know:

• What is the person, place, and time understudy?
• What statistics can the team use to describe the problem of esophageal
cancer in AZ?
• How do we get the descriptive cancer data from the registry?
• Does the registry contain the exposure information (e.g., arsenic levels
or other environmental exposures)?
• Does registry information tell us about the association between cancer
and arsenic in the drinking water?

documents
What data does the researcher need?
• Person
AI/AN esophageal cancer cases1

• Place
Arizona state

• Time
1995-2004
Data lag, limited to what is available2

2Cancer data takes at least 18 months to check for completeness from the central registry.
http://azdhs.gov/phs/azchaa/CHAA_FAQ.pdf

documents
What statistics do we use to determine the
risk of esophageal cancers among AIs in AZ?
Use age-adjusted incidence rates:
• Risk of getting disease
• Comparisons of groups

Use 95% confidence intervals:
• Rate differences are statistically significant
• Magnitude of the difference
• Stability of the rates1

1Rates may be unreliable with small numbers of cases. The 95% CIs will be a wide range.

documents
The Cancer Data Query
System, incidence rates
can be access in two
ways:
Incidence rates

– ACR CHAA Maps

documents

Age-adjusted incidence rates
of esophageal cancer
per 100,000
• All AZ residents 1995-2009:
– 4.3 per 100,000 (95% CI: 4.0-4.9)

• All AZ men:
– 1995: 6.9 (95% CI: 5.5-8.3)
– 2009: 8.0 (95% CI: 6.8-9.2)

• All AZ women:
– 1995: 1.6 (95% CI: 0-2.2)
– 2009: 1.7 (95% CI: 1.1-2.3)

documents

Age-adjusted incidence rates of
esophageal cancer
per 100,000 among AIs
• All American Indians AZ 1995-2009:
– 3.0 per 100,000 (95% CI: 2.1-3.8)

• American Indian men in AZ:
– 1995: 6.6 (95% CI: 0-15)
– 2009: 5.0 (95% CI: 0-10.8)

• American Indian women in AZ:
– 1995: 3.5 (95% CI: 0-9.1)
– 2009: 3.1 (95% CI: 0-7.3)

documents
What is the researchers story for the proposal?
• In AZ, the age-adjusted incidence rate of esophageal cancer is 4.3
per 100,000 (95% CI: 4.0-4.9) from 1995-2009

• Among AIs in AZ, the age-adjusted incidence rate of esophageal
cancer of 3.0 per 100,000 (95% CI: 2.1-3.8) from 1995-2009, which
is lower than the state rate; and, the difference is statistically
significant.

• The registry does not include environmental exposure information
like arsenic

• The registry information does not tell us about associations with
exposure and disease risk

Summary

• Overview of Inter Tribal Council of
Arizona (ITCA), Inc. Tribal Epidemiology
Center (TEC)

• Epidemiology Basics

• Practical Applications of Epidemiology
– Data Scenarios 1 & 2

2214 North Central Avenue, Phoenix, Arizona 85004
p 602.258.4822, f 602.258.4825

www.itcaonline.com

More Statistical Tests

P-values
• Estimated probability of rejecting the null
hypothesis (H0) of a study question.
• Null hypothesis is usually a hypothesis of "no
difference"
– Ex: there is no difference between high perceived risk and low
perceived risk groups
• Alternative hypothesis is a hypothesis of
“difference”
– Ex: there is a difference between high perceived risk and low
perceived risk groups

Statistical Tests

P-values
• To be statistically significant, the p-value
will usually be set to less than 0.05 (p <
0.05)
• If the p-value is less than 0.05, then the
null hypothesis can be rejected and the
alternative hypothesis can be accepted

Statistical Tests

95% Confidence Intervals (95% CIs)
• A CI consists of a range of values that act as
good estimates of the unknown population
parameter
– Ex: A 95% CI is the interval that you are 95% certain
contains the true population value as it might be
estimated from a much larger study.
• It is used to indicate if a measure is statistically
significance of an estimate

Statistical Tests

95% Confidence Intervals (95% CIs)
• Can tell us about the magnitude of measure
– Wide vs. narrow intervals
– Wide intervals can indicate small sample or low
power
– Whether the measure is reliable

Public Cancer Data
Resources
Public cancer data resources
• National Program of Cancer Registries (NPCR)
http://www.cdc.gov/cancer/npcr/
• Surveillance Epidemiology and End Results (SEER)
http://seer.cancer.gov/
• National Cancer Data Base (NCDB)
http://www.facs.org/cancer/ncdb/
• Behavioral Risk Factor Surveillance Survey (BRFSS)
http://www.cdc.gov/brfss/
• Agency for Healthcare Research and Quality – Library
http://www.ahrq.gov/clinic/ehclibrary/reslibcancer.htm

• PubMed
http://www.ncbi.nlm.nih.gov/pubmed/

Annual Arizona Conference for Tribal BCCEDP Collaboration, Flagstaff, AZ

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