Part B doesn't make sense to me. I believe there's a miscalculation in the author's work but I'd like to get some explanation

 

 

Lab 6: Rate Standardization
Part A. Direct Adjustment: Multiple Sclerosis in 3 US communities.
World and US Age Distributions from 2000 that were used in the Noonan article are provided
below. These data are from Klein and Schoenborn, 2001 and Zivadinov et al., 2003.
Link to Noonan Article (for Lorain County, Ohio information):
http://www.cdc.gov/pcd/issues/2010/Jan/08_0241.htm Age (years)
<30
30-39
40-49
50-59
60-69
>=70
Total US Standard
Population
(2000)
114,763
41,691
42,285
30,531
20,064
25,300
274,634 US Population
Proportion (2000)
0.42
0.15
0.15
0.11
0.07
0.09
1.0 World Standard Population
Proportion (2000)
0.56
0.12
0.12
0.09
0.07
0.04
1.0 1. (a) Using the age-specific rates for Lorain County, Ohio and both the US and world
population data from above, apply direct standardization to compute the US and world
age-adjusted rates for this region. Age
<30
30-39
40-49
50-59
60-69
>=70
Total Rate in
Lorein
8.60
80.03
212.43
306.55
189.68
142.86
112.41 US std
3.59
12.15
32.71
34.08
13.86
13.16
109.55 world std
4.82
9.60
25.49
27.59
13.28
5.71
86.49 Page 1 of 7 Revised 2/27/13 (b) Compare your results from (a) with the results shown on page 8 of the article. Results are the same in my calculations and table.
2. Why do you think the authors did not adjust for sex in the data presented in the Table
(i.e., page 8)?
It is possible that the author was interested of bringing awareness to the overall population
regardless of the sex and that is why they did not use it. However, it is evident that it is more
prevalent in females and sex standardization would have been more reliable to truly compared
among states. 3. Why do the US age-adjusted and world age-adjusted rates differ?
Because proportions are different in each region. It is more prevalent in the world for people <30 but
it is slightly higher in the US for people between 30-59. 4. (a) What is another term for unadjusted rate?
Crude rate
(b) What are other terms for age-, sex- and race- adjusted rates?
Standardized rate Page 2 of 7 Revised 2/27/13 Part B. Indirect Adjustment: Cancer Deaths In Desert Springs At a social gathering in 1978 in Desert Springs, a desert retirement community of less than
10,000 people, one of the local physicians commented to the mayor that there appeared to be
an excessive number of cancer deaths ever since a nuclear power plant was constructed in the
desert 10 miles north of town. Upon hearing this alarming news, the mayor contacted the
director of the local health department who informed him that last year there were 44 deaths
among Desert Springs residents due to malignant neoplasms. No information was given on
either the age or sex of the decedents. An abbreviated census was conducted in Desert Springs
two years prior in which basic demographic information was gathered on the local residents.
After reading in the newspaper that the rate of malignant neoplasms during 1976 in the
United States was 175.8 per 100,000 population, the mayor calculated that there should be
only 16 cancer deaths per year among the 8,907 persons living in Desert Springs. Since 44
deaths were observed, there were 28 more deaths than would be expected based on the U.S.
mortality rates.
B.1. Does the mayor's concerns over the excessive cancer deaths appear justified?
______Yes ___X___No
Explain your answer:
No, because the number of death is in the population older than 50, which is ~50% in this
town.
In order to assist the mayor, we need to determine if the 44 deaths observed among Desert
Springs residents are excessive or if they are due primarily to the unusual age structure of the
retirement community. Using information from the local census and age-specific mortality
rates due to malignant neoplasms for the United States in 1976, we construct the following
table:
1976 Population of
Desert Springs Death Rate per 100,000
Total Malignant
Neoplasms, USA, 1976 0-4 520 4.9 5-14 879 5.0 15-24 731 6.5 25-34 694 14.5 35-44 535 51.5 45-54 829 182.0 55-64 912 438.4 65-74 2002 786.3 75-84 1372 1248.6 85+
Total 433
8907 1441.5
4179 Age Group Expected Deaths in
Desert Springs
0.3
0.5
0.5
1.1
3.1
16.9
44.9
176.7
192.3
70.1 507 Page 3 of 7 Revised 2/27/13 The Standardized Mortality Ratio (or Comparable Morbidity Ratio) is frequently used to
evaluate the effect of indirect adjustment. The Standardized Mortality Ratio (SMR) is defined
as: SMR Total # of observeddeathsin population 100% or Total # of expecteddeathsin population Observed
100%
Expected ***Note: Multiplying by 100% is often ignored. If the ratio is greater than 1, it means that more
deaths are observed than would be expected (and vice versa if the ratio is less than 1).***
B.2. Based on the age-specific population in Desert Springs and the age-specific U.S.
mortality rates for malignant neoplasms, calculate the expected deaths in Desert
Springs by age group. Note that we make the assumption that Desert Springs would
have the same age specific cancer mortality rates as the entire nation.
_____507____Total expected deaths
B.2.1. Calculate the expected death rate in Desert Springs if the U.S. mortality rates
applied. Age Group
0-4
5-14
15-24
25-34
35-44
45-54
55-64
65-74
75-84
85+
Total Expected Deaths in
Desert Springs
0.3
0.5
0.5
1.1
3.1
16.9
44.9
176.7
192.3
70.1 507 B.2.2. Compute the ratio of the rates in B.2.1, i.e., divide the crude death rate in Desert
Springs by the expected death rate. Interpret this ratio.
Crude = 44 expected = 507
44/507 = 0.087 the ratio tells us that actual death rate is very low. Page 4 of 7 Revised 2/27/13 B.3. Determine the Standardized Mortality Ratio (SMR) for malignant neoplasms in
Desert Springs. _____8.7%____SMR
B.3.1. How does the SMR compare to the ratio you calculated in question B.2.2? (They
should be the same. Why?)
It is the same because it is comparing the same thing.
B.4. Do the data suggest that there are excessive cancer deaths in Desert Springs once
the confounding effects of age are controlled? Yes or No? Explain your response.
No, it does not suggest that there is an excessive cancer deaths despite having a high
percentage of population older than 50 when cases are more prevalent.
B.5. If subsequent information were made available which showed that, in a given year,
there were 4 malignant neoplasm deaths among those less than 15 years of age, would
you be concerned? Yes or No? Explain your response.
Yes, there should be a concern because the cases in this population should be very very low. Page 5 of 7 Revised 2/27/13 Part C: Direct and Indirect Methods: Bladder Cancer Age Bladder Cancer
Cases in
Birmingham,
1969-71 0-54
55-59
60-64
65-69
70-74
75+
Total 4
4
8
9
6
21
52 Females in
Birmingham,
1970 Bladder
Cancer Cases
in Detroit,
1969-71 Females
in Detroit,
1970 306137
20483
18627
16195
11713
16580
389735 57
42
49
55
59
123
385 1775268
102807
82053
66436
53246
72573
2152383 US Female
Bladder
Cancer Rates,
1970 (per
100,000)
1.1
12.2
15.8
24.8
35.7
52.7
6.3 C.1. Compute the crude annual incidence rates for bladder cancer in females in Detroit
and Birmingham during this time period. What is the ratio of the incidence of bladder
cancer in Detroit females compared to that in Birmingham females?
NOTE: The number of incident cases is reported over a three-year period, while the population is
estimated over a one-year period. Thus, in order to estimate the annual incidence, you will need to
assume that each member of the population has been followed for 3 years (i.e. that the population can
be multiplied by 3 to represent the population at risk over a 3 year period). Therefore, the annual
incidence rate for 0 to 54-year-olds in Birmingham would be calculated as: 4/(3 * 306,137) =
4/918,411, and so on. You will need to remember this for all of the calculations in Part C. 4.45 for
5.96 for Detroit
4.45/5.96*100 =
higher in Age
0-54
55-59
60-64
65-69
70-74
75+
Total Incidence rate
in Birmingham
0.435534853
6.509463132
14.31613607
18.52423588
17.07504482
42.21954162
4.447466441 incidence rate
in 1.07026094
Detroit
13.6177498
19.9058332
27.5954804
36.9354819
56.4948397
5.96238371

Birmingham vs
75% it is 25%
Detroit. C.2. We will now compare the annual incidence rates for female bladder cancer in each
of the two cities. Use the Birmingham female population as a standard to calculate the
age-adjusted rates in Detroit using the direct method. That is, apply the age-specific
rates in Detroit to the age specific populations of Birmingham to calculate the number
of cancers that would be expected in Detroit if its population had the same age
structure as Birmingham. Note that the population of Birmingham will serve as the
denominator for this hypothetical rate. Page 6 of 7 Revised 2/27/13 Age
0-54
55-59
60-64
65-69
70-74
75+ Age adjusted
rate
in Detroit
0.011653399
2.216106001
3.562182714
5.679835415
10.51125014
11.35802969 C.3. Using the rates calculated in question 2, what is the ratio of the age-adjusted
incidence of bladder cancer in Detroit females compared to Birmingham females?
Explain specifically why the ratio of the adjusted incidence rates differs from the crude rates
calculated in question 1.
The ratios are lower in Detroit than in Birmingham. It differs due to the difference in the
populations but once adjusted we can see that Detroit has less incidence. C.4. What are the respective standardized incidence (morbidity) ratios for bladder
cancer for Detroit females and Birmingham females, compared to US females? What
additional information do these calculations provide that would be helpful to the City
Council in evaluating this problem?
Age
0-54
55-59
60-64
65-69
70-74
75+ Incidence
rate in
39.5940775
6
53.3562551
8
90.6084561
7
74.6944995
47.8292572
80.1129821
9 incidence
rate in
97.29644917
111.6208997
125.9862862
111.2720982
103.4607335
107.2008343 They are lower much lower. It could help with prevention methods used in this cities. Page 7 of 7 Revised 2/27/13

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