topic 5: rates and standardization modified from the notes of a. kuk p&g pp. 66—95
TRANSCRIPT
Topic 5: Rates and Standardization
Modified from the notes of A. Kuk
P&G pp. 66—95
Demographic Data
Size of population and its composition by gender, race, age etc
Vital Statistics
Vita --- life
Tell a story of life with numbers so that vital services can be provided --- food, lodgings, health, water, etc
• Births
• Natural Increases
• Marriages
• Divorces
• Diseases
• Deaths
Complex and massive storybecause we often need to dealwith whole countries.
• Describe health status of a population • Spot trend• Make projections• Planning• Set policy• Compare groups
Want to be able to:
Provisional statistics USA 12 months ending in April(millions) 1993 1994 1995
Live births
4.075 4.017 3.966
Deaths 2.207 2.280 2.297
Increase 1.868 1.737 1.669
Marriages
2.352 2.330 2.345
Divorces 1.203 1.185 1.179
Infant deaths*
33,700 32,400
31,100
Mortality in US
0
500000
1000000
1500000
2000000
2500000
1940 1950 1960 1970 1980 1990 2000
year
de
ath
s
Deaths
Mortality by sex
0200,000400,000600,000800,000
1,000,0001,200,0001,400,000
1940 1950 1960 1970 1980 1990 2000
year
de
ath
s
Male Female
Death rate increasing?
numeratorRate = per time unit
denominator
• “Crude” rate, single number, summary
• allows for standardization
• makes comparisons more meaningful
State of Massachusetts in 1992 Number
Population 6,060,943
Live births 87,202
Deaths: Total 53,804
Under 1 year 569
Crude birth rate per 1000 persons per year 39.141000606094387202
multiplier
Crude death rate per 1000 persons per year
Infant mortality rate per 1000 live births per yr
88.81000606094353804
5.6100087202
569
Ratea
Per 1,000 1993 1994 1995
Live births 15.9 15.5 15.2
Fertility rateb
69.0 67.9 66.8
Deaths 8.6 8.8 8.8
Increase 7.3 6.7 6.4
Marriages 9.2 9.0 9.0
Divorces 4.7 4.6 4.5
Infant deathsc
8.3 8.2 7.9
a=pop., b=women 15-44, c=live births
US Mortality Rate
0
200
400
600
800
1000
1200
1940 1950 1960 1970 1980 1990 2000
year
Pe
r 10
0,00
0
Rates
US Mortality Rate by Sex
0200400600800
100012001400
1940 1950 1960 1970 1980 1990 2000
year
Pe
r 10
0,00
0
Male Female
Crude rate answer all questions?
Status Popn Impair’s Rate/100,000
Employed 98,917 552 5.58
Unemployed 7,462 27 3.62
Not in labor force
56,778 368 6.48
Total 163,157
947 5.80
Therefore it is better to be “employed” than “not in the labor force”as far as hearing is concerned
Confounders?
Age distribution
Employed Not in labor force
Age Popn Percent Popn Percent
17-44 67,987
68.7 20,760 36.6
45-64 27,592
27.9 15,108 26.6
65+ 3,338 3.4 20,910 36.8
Total 98,917
100.0 56,778 100.0
Age Composition of Population
Age Popn Impairs Rate
/1000
17-44 94,930 441 4.65
45-64 43,857 308 7.02
65+ 24,370 198 8.12
Total 163,157 947 5.80
Age Specific Impairment RatesCurrently employed
Age Popn Impairs Rate
/1000
17-44 67,987 346 5.09
45-64 27,592 179 6.49
65+ 3,338 27 8.09
Total 98,917 552 5.58
Age Specific Impairment RatesNot in labor force
Age Popn Impairs Rate
/1000
17-44 20,760 80 3.85
45-64 15,108 117 7.74
65+ 20,910 171 8.18
Total 56,778 368 6.48
Age Specific Impairment Rates
Age Employed
/1000
Not in labor force /1000
17-44 5.09 3.85
45-64 6.49 7.74
65+ 8.09 8.18
Total 5.58 6.48
Can we capture what is happening with a single number?
Problem caused by different age profiles.
Standardize
•Direct
• Indirect (skipped)
Direct method of getting rid ofage confounder is to standardizethe age distribution and apply theappropriate age specific rates.
Select a standard age distribution.
Logical choice is the total population
For Currently Employed
Age Popn Rate
/1000
Expected
Impairs
17-44 94,930 5.09 483.2
45-64 43,857 6.49 284.6
65+ 24,370 8.09 197.2
Total 163,157 965.0
965.0Age adjusted rate = 5.91 per 1,000
163,157=
For those not in labor force
Age Popn Rate
/1000
Expected
Impairs
17-44 94,930 3.85 365.5
45-64 43,857 7.74 339.5
65+ 24,370 8.18 199.3
Total 163,157 904.3
904.3Age adjusted rate = 5.54 per 1,000
163,157=
Crude rate Not in labor force > Employed
Age adjusted Not in labor force < Employed
Remember
1. This is a construct.
2. Choice of standard distribution is arbitrary.
US Mortality Rate and Adjusted Rate
0
200
400
600
800
1000
1200
1940 1950 1960 1970 1980 1990 2000
year
Pe
r 10
0,00
0
Adjusted Rates
US Mortality Rate and Adjusted Rate by Sex
0200400600800
100012001400
1940 1950 1960 1970 1980 1990 2000
year
Pe
r 10
0,00
0
Male Female Male Adj. Female Adj.
Age-Adjusted Cancer Death Rates, Males by Site, US, 1930-1996
Adjusted using the U.S. population in 1940 as the standard distribution
Age-Adjusted Cancer Death Rates, Females by Site, US, 1930-1996
When to use adjustment:
Check that the age-specificrates follow more or less thesame trend for all thepopulations to be compared.
Is there a confounder?Age?Sex?
go go
so so
no no