You have been given the following table from a prospective study of deaths in tu
ID: 128121 • Letter: Y
Question
You have been given the following table from a prospective study of deaths in tunnel and bridge workers in New York City. NYC Tunnel Workers NYC Bridge Workers Age Person- #Deaths | Age-Specific | Age | Person-!#Deaths Age-Specific Category Years Observed Mortality Years Observed Mortality er er 11,000 1,000 3,500 1,500 7,500 3,500 32,000 2,000 14,000 2,000 20,000 7,500 4 16 12 32 32 Total Total Crude Mortality (Tunnel) Crude Mortality Ratio: Crude Mortality (Bridge) Calculate the crude mortality rates and the crude mortality ratio (reference group - bridge workers) Interpret these results a. b. Fill the age-specific mortality rates in the table and interpret these results c. Using the table below, calculate the age-adjusted mortality rates and the age-adjusted mortality ratio (reference - bridge workers) using the combined person-years for the two groups as the standard population Iplease show vour work in detaill. Briefly explain what vou did and briefly discuss what these results mean TUNNEL WORKERS BRIDGE WORKERS Combined Standard Population 43,000 3,000 17,500 3,500 27,500 11,000 105,500 Age Category Age-SpecificExpected Deaths ExpectedAge-Specific Mortality Age Category Mortality Deaths 2 2 4 4 6 6 Total TotalExplanation / Answer
a. NYC Tunnel workers
Age category
Person in years
Death observed
Age-specific Mortality
1
11000
11
2
1000
5
3
3500
5
4
1500
18
5
7500
9
6
3500
32
Total
28000
80
Crude Mortality Rate = Number of death/ Total population*10n
Crude Mortality Tunnel = 80/28000*100000
= 286 death per 100000 population.
NYC Bridge Work:
Age
Persons-years
Death observed
Age-specific Mortality
1
32000
15
2
2000
5
3
14000
11
4
2000
16
5
20000
12
6
7500
32
Total
77500
91
Crude Mortality Bridge = 91/77500*100000
= 117 deaths per 100000 population.
Crude Mortality Ratio: No of death/ total population *100
= 403/105500*100
Crude ratio= 0.38.
Interpretation:
The Mortality rate of tunnel group is more when compared to Bridge group in the given population.
b. Age-specific Mortality Rates:
Age-specific mortality rate = No of deaths in the age category/ Total no of population in that age group*100000
NYC Tunnel Workers:
Age category
Person in years
Death observed
Age-specific Mortality per 100000 population
1
11000
11
100
2
1000
5
500
3
3500
5
142
4
1500
18
1200
5
7500
9
120
6
3500
32
914
Total
28000
80
NYC Bridge workers:
Age
Persons-years
Death observed
Age-specific Mortality per 100000 population
1
32000
15
46
2
2000
5
250
3
14000
11
78
4
2000
16
800
5
20000
12
60
6
7500
32
426
Total
77500
91
Interpretation: In NYC bridge workers have the high age-specific mortality rate of 800 in the age group of 4 whereas the NYC tunnel workers have age-specific mortality rate 1200 in the age category of 4. This shows the age category 4 has the high age-specific mortality rate in both tunnel and bridge workers.
c. First, find the expected death.
Expected deaths = Age-specific death* combined standard population/ Total Standard population.
Tunnel workers Bridge workers
Age category
Age-specific Mortality
Expected Deaths
Combined standard population
Expected Deaths
Age-specific Mortality
Age category
1
100
40
43000
18.7
46
1
2
500
14.2
3000
7.1
250
2
3
142
23
17500
12.9
78
3
4
1200
39.8
3500
26.5
800
4
5
120
31.2
27500
15.6
60
5
6
914
95
11000
44.4
426
6
Total
2976
243.2
105500
125.2
1660
Age-Standardized Mortality = Observed death/ Expected death
Age-Standarized Mortality(Tunnel) = 2976/243.2 = 12.23
Age-standardized Mortality (Bridge) = 1660/125.2 =13.2
d.
Tunnel Worker Bridge worker
Age category
Age-specific Mortality
Observed deaths
Expected death
Age category
1
100
18.7
1
2
500
7.1
2
3
142
12.9
3
4
1200
26.5
4
5
120
15.6
5
6
914
44.4
6
Total
2976
91
15.2
Indirect Standardized Death Rate the predefined values of ASRD in the standard population are used in the actual age category of the study population.
Standarized Mortality ratio = 195.
Age category
Person in years
Death observed
Age-specific Mortality
1
11000
11
2
1000
5
3
3500
5
4
1500
18
5
7500
9
6
3500
32
Total
28000
80
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