how do cancer rates in your area compare to those in other areas?
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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. Rates. - PowerPoint PPT PresentationTRANSCRIPT
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
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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
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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
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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
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Age specific rates
Gender specific rates
Race specific rates
Cause specific rates
Site specific rates
Examples of Specific Rates
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Lung Cancer Deaths by Age Group, United States, 1995
15,420 xxx188,500,741Total12,356
2,709
303
41
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Lung Cancer Deaths
12,356 / 31,078,760 = 39.762,709 / 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
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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
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(1) / (2) x (4) = (5)(4)(1) / (2) = (3)(2)(1)
226,500,000xxx45,000115Total25,700,00015,00010065+
140,300,00025,0001019-64
60,500,0005,00050-18
Expected Number of
Deaths
1980 U.S.Standard
PopulationASRPopulation
at riskCancer DeathsAge
Creating a cause-specific, age-adjusted death rate using direct standardization
Crude Rate(115 / 45,000) x 1000
2.56 per 1,000
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(3) x (4) = (5)(4)(1) / (2) = (3)(2)(1)
288,039226,500,000xxx45,000115Total171,41925,700,0006.67 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
PopulationASRPopulatio
n at riskCancer DeathsAge
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
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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
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Standard Population
By convention, SEER uses the 1970 US standard population
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Cancer Death Rates by State per 100,000, 2000
212Dist. Of Col.178Massachusetts163Connecticut195Delaware178Indiana162Washington193Louisiana 178Illinois160Iowa192Kentucky 177Virginia159Montana185Maine177Pennsylvania159Kansas184West Virginia176Missouri157Wyoming 184Nevada175North Carolina156Minnesota184Maryland175Georgia156California
182Mississippi173Michigan155South Dakota181Tennessee172Vermont155North Dakota181New Hampshire170Oklahoma 155Nebraska181Arkansas169New York155Arizona180Ohio168Texas148Idaho179New Jersey167Alaska146New Mexico179Alabama166Oregon142Colorado178South Carolina166Florida133Hawaii178Rhode Island163Wisconsin122Utah
Average annual mortality 1992-1996, age-adjusted to 1970United States = 170 per 100,000
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Age-adjusted death rates per 100,000
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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)
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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
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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
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Observational Studies Cohort Studies Case-Control Studies
Experimental Studies Randomized Control Trials
(RCT / Clinical Trials)
Analytic Studies (to test hypotheses)
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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
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Disease-FreeCohort
Single Sample Cohort Study Design
Target Population
Exposed
Not Exposed
Diseased
Not Diseased
Diseased
Not Diseased
Time
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Multi-Sample Cohort Study Design
Study Cohort
Exposed
Not Exposed
Diseased
Not Diseased
Diseased
Not Diseased
Time
Control Cohort
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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