Topic 5: Rates and Standardization Modified from the notes of A. Kuk P&G pp. 66—95

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