1. Measures of Mortality Part 2
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2. Outline:
Standardization
Direct adjusted rates
Indirect adjusted rates

3. Standardization
A principal role in demography is to compare the mortality between two or more populations.
The comparison of crude mortality rates is misleading.
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4. If the populations being compared differ greatly with respect to , for example, age or sex, that will affect the overall rate of morbidity or mortality.
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5. For example, age is an important determinant of mortality.
An older population will have a higher overall mortality rate than a younger population.
As a result, variations in age will complicate any comparison between two or more populations that have different age structures.
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6. This is achieved by using methods of standardization.
One way to overcome this problem is to combine category specific rates into a single summary rate that has been adjusted to take into account its age structure.
This is achieved by using methods of standardization.
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7. Methods of Standardization
There are two methods of standardization commonly used:
1- Direct method
2- Indirect method
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8. Direct Adjusted Rates
Requires a standard population, to which the estimated age-specific rates can be applied
Choice of the standard population may affect the magnitude of the age-adjusted rates, but not the ranking of the population

9. How to calculate standardized crude death rate?
1- Select a standard population, whose age distribution will be the standard for comparison.
2- calculate age specific death rate for the two populations (A and B).
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10. 3- Calculate the expected number of deaths that would occur in a year if the standard population experienced the age-specific death rates (ASDR) of populations A and B.
4- Multiply each age group in the standard population by the corresponding ASDR for populations A and B.
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11. 6- To calculate the age-standardized crude rate for each population:
5- Add the columns of the expected deaths for the two populations (A & B) to obtain the total expected deaths in the standard population.
6- To calculate the age-standardized crude rate for each population:
Divide the total expected deaths for each population by total standard population.
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12. Population, Deaths, and Death Rate by Community and by Age
Community B
Age
(year)
Population
Deaths
Death Rate
(per 1000)
Under 1
1,000 15
15.0
5,000
100
20.0
1 – 14
3,000 3
1.0
20,000 10
0.5
15 – 34
6,000 6
35,000 35
35 – 54
13,000 52
4.0
17,000 85
5.0
55 – 64
7,000
105
8,000
160
Over 64
1,600
80.0
15,000
1,350
90.0
All ages
50,000
1,781
35.6
100,000
1,740
17.4
Death Rate
(per 1000)
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13. Age – adjusted death rate (per 1000)
(years)
Standard population
Death rate
in A
(per 1,000)
Expected deaths at
A’s rate
in B
B’s rate
Under 1
6,000
15.0 90
20.0
120.0
1 – 14
23,000
1.0 23
0.5
11.5
15 – 34
41,000 41
41.0
35 – 54
30,000
4.0
120
5.0
150.0
55 – 64
15,000
225
300.0
Over 64
35,000
80.0
2,800
90.0
3,150
Total
150,000
35,6
3,299
17.4
3,772.5
Age – adjusted death rate (per 1000)
22.0
25.0
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14. x 1000 Calculation of standardized death rate
Total standard population = 150,000
Expected deaths for pop A = 3299
Standardized death rate for pop A =
Expected deaths pop A
x 1000
Total standard population
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15. standardized death rate for pop A:
3299
x 1000
= per 1000
150,000
The result indicates that pop A crude death rate would be 21.99/1000 if it has the same age structure as the standard population which far less than the observed crude death rate 35.6/1000.
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16. standardized death rate for pop B:
Total standard population = 150,000
Expected deaths for pop B = 3,772.5
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17. Standardized death rate for pop B =
Expected deaths pop A
x 1000
Total standard population
3,772.5
x 1000
= per 1000
150,000
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18. The result indicates that pop B crude death rate would be 25
The result indicates that pop B crude death rate would be 25.15/1000 if it has the same age structure as the standard population which far more than the observed crude death rate 17.4/1000.
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19. The result indicates that pop A crude death rate would be 21
The result indicates that pop A crude death rate would be 21.99/1000 if it has the same age structure as the standard population which far less than the observed crude death rate 35.6/1000.
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20. This ratio is called the Comparative Mortality Ratio (CMR).
We can calculate: The ratio of the directly standardized rates to provide a single summary measure of the difference in mortality between the two populations.
This ratio is called the Comparative Mortality Ratio (CMR).
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21. Comparative Mortality Ratio (CMR)
calculated by dividing the overall age adjusted rate in country B by that of A.
In our example:
Comparative Mortality Ratio (CMR)
= 25.15/21.99 = 1.14
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22. This CMR is interpreted as:
after controlling for the affects of age, the mortality in Country B is 14% higher than in country A.
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23. Example 2:
Table 2 presents crude mortality data for two populations (countries A and B).
The overall crude mortality rate is higher for country A (10.5 deaths per 1,000 person years)
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24. compared with country B (7 deaths per 1,000 person years).
Notice the ASDRs rates being higher among all age-groups in country B.
For example, 18% of the population in country A are aged over 60 years compared with 6% in country B.
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25. Table 2. Crude mortality rates stratified by age for two populations (country a, B).
Country B
Age group
# deaths/
1000
Pop (M) in millions
Death rate
# deaths
Pop
Death rate/
0 - 29
7,000 6
1.2
6,300
1,500,000
4.2
20,000
5.5
3.6
3,000
550,000
60+
120,000
2.5 48
6,000 50
Total
147,000 14
10.5
15,300
2,170,000 7

26. Country A has a much older population than country B.
The reason for the difference between the crude mortality rates between country A and country B is that these two populations have markedly different age-structures.
Country A has a much older population than country B.
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27. Table 3. Standard population
Age group
Pop
0 - 29
100,000
65,000
60+
20,000
Total
185,000
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28. Age
(years)
Standard population
Death rate
in A
(per 1,000)
Expected deaths at
A’s rate
in B
B’s rate
0 - 29
100,000
1.2
120
4.2
420
65,000
3.6
234
5.5
357.5
60+
20,000 48
960 50
1,000
Total
185,000
10.5
1,314 7
1,777.5
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29. x 1000 Calculation of standardized death rate
Total standard population = 185,000
Expected deaths for pop A = 1314
Standardized death rate for pop A =
Expected deaths pop A
x 1000
Total standard population
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30. 1314 x 1000 = 7.1 per 1000 185,000 standardized death rate for pop A:
The result indicates that pop A crude death rate would be 7.1/1000 if it has the same age structure as the standard population which is less than the observed crude death rate 10.5/1000.
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31. x 1000 Calculation of standardized death rate
Total standard population = 185,000
Expected deaths for pop A =
Standardized death rate for pop B =
Expected deaths pop A
x 1000
Total standard population
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32. standardized death rate for pop B:
1777.5
x 1000
= 9.6 per 1000
185,000
The result indicates that pop A crude death rate would be 9.6/1000 if it has the same age structure as the standard population which is more than the observed crude death rate 7/1000.
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33. We can calculate the Comparative Mortality Ratio (CMR) as:
= 9.6/7.1 = 1.35
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34. CMR is interpreted as:
After controlling for the affects of age, the mortality in Country B is 35% higher than in country A.
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35. Indirect Adjustment of Rates
Used if age-specific rates cannot be estimated.

36. Indirect Adjustment of Rates
Based on applying the age-specific rates of the standard population to the population of interest to determine the number of “expected” deaths.
Steps in calculation:
1- Choose standard population and list its age-specific death rate.
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37. Suppose we selected population B as the standard population.
List ASDR for population B.
List the age distribution of the pop A in the next column.
Calculate expected deaths for pop A by multiplying each age group by the corresponding ASDR for the standard population.
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38. Sum the column of the expected deaths.
This total shows the number of deaths that would occur if population A experienced the ASDR of pop B.
Calculate the standardized mortality ratio as:
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39. ____________________
Standardized Mortality Ratio(SMR)=
Total observed deaths
In population (A)
____________________
Total expected deaths
in a population (A)
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40. Standard death rate pop B Expected deaths in A at standard rates
Age
(years)
Standard death rate pop B
(per 1,000)
Total population A
Expected deaths in A at standard rates
Observed Deaths A
Under 1
20.0
1,000 15
1 – 14
0.5
3,000
1.5 3
15 – 34
1.0
6,000
6.0 6
35 – 54
5.0
13,000
65.0 52
55 – 64
7,000
140.0
105
Over 64
90.0
20,000
1,800.0
1,600
Total
17.4
50,000
2,032.5
1,781
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41. SMRA = 1781 / = 0.876
The result shows that the observed deaths in A were 12% lower than they would have been if A ASDR were the same as those of pop B.
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42. Standardized Mortality Ratio
The ratio is exactly 1 if the observed and expected deaths are the same.
If the SMR is greater than 1, more deaths have occurred than anticipated.
If SMR is less than 1, fewer deaths have occurred than anticipated.
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43. Example 2:
Table 2 presents crude mortality data for two populations (countries A and B).
The overall crude mortality rate is higher for country A (10.5 deaths per 1,000 person years)
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44. compared with country B (7 deaths per 1,000 person years).
Notice the ASDRs rates being higher among all age-groups in country B.
For example, 18% of the population in country A are aged over 60 years compared with 6% in country B.
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45. Table 2. Crude mortality rates stratified by age for two populations (country a, B).
Country B
Age group
# deaths/
1000
Pop (M)
Death rate
# deaths
Pop
Death rate/
0 - 29
7,000 6
1.2
6,300
1,500,000
4.2
20,000
5.5
3.6
3,000
550,000
60+
120,000
2.5 48
6,000 50
Total
147,000 14
10.5
15,300
2,170,000 7

46. Country A has a much older population than country B.
The reason for the difference between the crude mortality rates between country A and country B is that these two populations have markedly different age-structures.
Country A has a much older population than country B.
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47. Table 3. Standard population
Age group
Pop
0 - 29
100,000
65,000
60+
20,000
Total
185,000
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48. Total expected deaths (E) 9,540
Table 3. Number of expected deaths if the population B had the same age-specific mortality rates as Country A.
Country B
Expected deaths
0 - 29
x 1,500,000 = 1,800
x 550,000 = 1,980
60+
0.048 x 120,000 = 5,760
Total expected deaths (E)
9,540
Total observed deaths (O)
15,300
Standardized Mortality Ratio (O/E) x 100
160
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49. An overall summary measure can then be calculated, that is, the standardized mortality ratio (SMR), which is the ratio of the observed number of deaths to the expected number of deaths.
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50. SMR =
Observed number of deaths (O) X 100%
Expected number of deaths (E)
SMR = 160 = 1.6 X 100 =
This means: The number of observed deaths in Country B is 60% higher than the number we would expect if Country B had the same mortality experience as Country A.
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