Upload
arron-jenkins
View
215
Download
1
Tags:
Embed Size (px)
Citation preview
How do cancer rates in your area
compare to those in other areas?
Understand the use of standardized rates, specific rates, and the limitations of computer mapping
2
Rates
Rates are standardized to a control population
Adjusted
Rates for specific segments/groups of the population (e.g. sex, age, race, cause of death, cancer site)
Specific
Summary rate of the actual number of observed events in a population over a given time period (e.g. all cancer deaths in 2000)
Crude
3
Crude Rates
Estimates the burden of disease in a
population
Not useful for making comparisons between
groups or examining changes over time,
because it depends largely on population
structure
4
Specific Rate Important because outcomes may be profoundly
affected by factors such as age, race, and gender
More precise indicator of risk than a crude rate as
it controls for a particular characteristic of interest
Allows for comparisons between strata or between
groups
5
Age specific rates
Gender specific rates
Race specific rates
Cause specific rates
Site specific rates
Examples of Specific Rates
6
Lung Cancer Deaths by Age Group, United States, 1995
15,420 xxx188,500,741Total
12,356
2,709
303
41
11
Lung Cancer Deaths
12,356 / 31,078,760 = 39.76
2,709 / 42,467,719 = 6.38
303 / 40,873,139 = 0.74
41 / 35,946,635 = 0.11
11 / 38,134,488 = 0.03
Age-Specific Lung Cancer Death Rate
Per 100,000
31,078,76045-54
42,467,71935-44
40,873,13925-34
35,946,63515-24
38,134,4885-14
PopulationAge (years)
Cause Specific Rate = (15,420/188,500,741) x 100,000 = 8.18 / 100,000
7
Adjusted Rate Specific rates are standardized to a control
population and are summarized to produce an
adjusted rate
Used to compare rates of entire populations taking
into account differences in population structure
(e.g., age, gender, race or other variables)
Adjusted rates can be compared if they are
calculated using the same standard population
8
(1) / (2) x (4) = (5)(4)(1) / (2) = (3)(2)(1)
226,500,000xxx45,000115Total
25,700,00015,00010065+
140,300,00025,0001019-64
60,500,0005,00050-18
Expected Number of
Deaths
1980 U.S.
Standard Population
ASRPopulation
at riskCancer Deaths
Age
Creating a cause-specific, age-adjusted death rate using direct standardization
Crude Rate
(115 / 45,000) x 1000
2.56 per 1,000
9
(3) x (4) = (5)(4)(1) / (2) = (3)(2)(1)
288,039226,500,000xxx45,000115Total
171,41925,700,0006.67 per 100015,00010065+
56,120140,300,0000.40 per 100025,0001019-64
60,50060,500,0001.00 per 10005,00050-18
Expected Number of
Deaths
1980 U.S.
Standard Population
ASRPopulation at risk
Cancer Deaths
Age
Age-Adjusted Rate
(288,039 / 226,500,000) x 1000
1.27 per 1,000
Crude Rate
(115 / 45,000) x 1000
2.56 per 1,000
Creating a cause-specific, age-adjusted death rate using direct standardization
10
If crude rate decreases after adjustment,
the study population is older than the
standard population
If crude rate increases after adjustment,
the study population is younger than the
standard population
Comparing Crude and Age-Adjusted Rates
11
Standard Population
By convention, SEER uses the 1970
US standard population
12
Cancer Death Rates by State per 100,000, 2000
212Dist. Of Col.178Massachusetts163Connecticut
195Delaware178Indiana162Washington
193Louisiana 178Illinois160Iowa
192Kentucky 177Virginia159Montana
185Maine177Pennsylvania159Kansas
184West Virginia176Missouri157Wyoming
184Nevada175North Carolina156Minnesota
184Maryland175Georgia156California
182Mississippi173Michigan155South Dakota
181Tennessee172Vermont155North Dakota
181New Hampshire170Oklahoma 155Nebraska
181Arkansas169New York155Arizona
180Ohio168Texas148Idaho
179New Jersey167Alaska146New Mexico
179Alabama166Oregon142Colorado
178South Carolina166Florida133Hawaii
178Rhode Island163Wisconsin122Utah
Average annual mortality 1992-1996, age-adjusted to 1970United States = 170 per 100,000
13
Age-adjusted death rates per 100,000
14
15
Cautions in Comparing Rates
Precision: Rates calculated from an area with a
small population are subject to a large amount of
variation from year to year
Comparability: Rates are affected by differences
in population structure (e.g., a county with more
older women may have higher rates for breast
cancer than a county with more younger women)
16
Advanced Topics
What types of investigations address cancer etiology
and control?
How do we evaluate whether cancer studies are
valid?
How do we assess whether associations between
cancer and risk factors are causal?
How much of the morbidity and mortality from
cancer might be prevented by interventions?
What types of investigations address
cancer etiology and control?
Understand case-control, cohort, and intervention studies
18
Descriptive Studies (to generate hypotheses)
Case-Reports / Series
Cross-Sectional Studies (Prevalence Studies)
measure exposure and disease at the same time
Ecological Studies (Correlational Studies) use group
data rather than data on individuals.
These data cannot be used to assess individual risk –
to do so is to commit Ecological Fallacy
19
Observational Studies
Cohort Studies
Case-Control Studies
Experimental Studies
Randomized Control Trials
(RCT / Clinical Trials)
Analytic Studies (to test hypotheses)
20
Cohort Study Design
A group of people (cohort) without disease are
identified and characterized by an exposure
Group is followed forward over a period of
time to observe the development (incidence)
of the disease of interest
21
Disease-FreeCohort
Single Sample Cohort Study Design
Target Population
Exposed
Not Exposed
Diseased
Not Diseased
Diseased
Not Diseased
Time
22
Multi-Sample Cohort Study Design
Study Cohort
Exposed
Not Exposed
Diseased
Not Diseased
Diseased
Not Diseased
Time
Control Cohort
23
Calculating Outcome Measures
Outcome
D
B
No Disease
(controls)
IN = C / (C+D)CNot Exposed
IE = A / (A+B)AExposed
IncidenceDisease
(cases)Exposure
Relative Risk = IE / IN