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A Brief Introduction to Epidemiology - IV (

Overview of Vital Statistics Demographic

Methods)

- Betty C. Jung, RN, MPH, CHES

Learning Objectives

- To understand the how vital statistics and

demographic data are used in Public Health - To understand the measures of mortality,

fertility, morbidity that are based on vital

statistics - To understand the basis for Rate Adjustment

Performance Objectives

- Basic understanding of how to use the most

commonly available health statistics to quantify

disease in Public Health Practice - Basic understanding of the most common vital

statistical measures encountered in Practice

Introduction

- Demographic data and vital statistics are useful

tools in - Determining a communitys health status
- Deciding whats the best way for providing health

services - Planning a public health program
- Evaluating a programs effectiveness

Demographic Data

- Demographic data include those variables that

describe the characteristics of a population

(i.e., population size and how it changes over

time)

Demographic Variables

- Population composition include
- Age
- Sex
- Income
- Occupation
- Health services use
- Geographic location
- Geographic density

Vital Statistics (Events)

- Include
- Births
- Deaths
- Marriages
- Divorces

Sources of Vital Statistics Demographic Data

in the U.S.

- Census
- Registration of Vital Events
- Morbidity Surveys

Demographic Data United States Census

- The United States conducts a decennial census

(every 10 years) since 1790. Each household and

resident is enumerated (counted). - Person info sex,age,race,marital status, place

of residence, and relationship to or position as

head of household - A systematic sample of households provides

income, housing, number of children born,

education, employment status, means of

transportation to work, and occupation.

Demographic Data United States Census

- Census tables are published for the entire U.S.,

each state, urbanized areas (Metropolitan

Statistical Areas MSAs), counties, cities,

neighborhoods (census tracts), and city blocks.

Demographic Data Annual Registration of Vital

Events

- In the U.S., state laws require that all vital

events be registered. - Birth certificates serve as proof of citizenship,

age, birthplace and parentage. - Death Certificates - required as burial documents

and in settlement of estates and insurance claims.

Demographic Data US Vital Statistics Data

- Vital Statistics of the United States - annual -

detailed tables of vital events by various

demographic characteristics and major geographic

subdivision. Data on marriages and divorces are

collected and published in a separate volume.

Demographic Data US National Death Index

- Prepared by NCHS - a nationwide, computerized

index of death records compiled from each states

vital statistics offices. - Allows researchers to decide if persons in their

studies have died. Includes death certificate

number, state person died in and date of death.

Demographic Data U.S. Morbidity Surveys

- Morbidity data (i.e., prevalence of disease)
- Communicable disease reports are shared through

CDCs Morbidity and Mortality Weekly Reports

(MMWR) - More serious diseases are well reported (i.e.,

cholera,plague,yellow fever, rabies, paralytic

polio)

Demographic Data U.S. Sources of Morbidity

Data

- Reportable diseases
- National Health Survey
- Hospital records data
- Industrial hygiene records
- School health records
- Medical care subgroups (i.e.,prepaid health

insurance plans) - Chronic Disease Registries (i.e., tumor

registries) - Insurance industry data

Vital Statistics Rates, Ratios, and Proportions

- Three rates used in vital statistics
- Crude rates - computed for an entire population
- Specific rates - consider differences among

subgroups, computed by age, race, sex or other

variables. - Adjusted (standardized) rates - to make valid

summary comparisons between two or more groups

with different age (or other) distributions.

Measures of Mortality

- Each rate is a measure of the relative frequency

of deaths that occurred in a given population

over a specific time period (time at risk). - Population size is usually defined as the

population at midyear (July 1). - These measures estimate the population at risk

(ab)/time(t) of one year. If this convention

cannot be met, then the calculation should really

be considered a proportion rather than a rate.

Measure of Mortality Annual Crude Death Rate

- Universally used as generalized indicator of a

populations health. - May not be truly reflective without accounting

for age, race, or sex. - Example
- State, Yr - population 5000 deaths 25
- Crude Death Rate 25/5000 x 1000
- 5 deaths per 1000 per year

Measure of Mortality Age-Specific Death Rate

- Defined as the number of deaths in a specific age

group in a calendar year, divided by the

population of the same age group on July 1 of

that year, the quotient multiplied by 1000. - Example
- Country, Yr - age group 25-34 yrs population

5,000,000 deaths 200,000 - Age-specific death rate 200,000/5,000,000 x

1000 - 40 deaths per 1000 population per year for

age group 25-34

Measure of Mortality Cause-Specific Death

Rate

- Defined as the number of deaths assigned to a

specific cause in a calendar year, divided by the

population on July of that year, the quotient

multiplied by 100,000 - Example
- Country, Yr - cause accidents population

5,000,000 deaths 4,000 - Cause-specific death rate 4,000/5,000,000 x

100,000 - 80 accidental deaths per 100,000 population

per year

Measure of Mortality Proportional Mortality

Ratio

- Defined as the number of deaths assigned to a

specific cause in a calendar year, divided by the

total number of deaths in that year, the quotient

multiplied by 100 - Example
- Country, Yr - total deaths from all causes

1,500,000 deaths from cancer 675,000 - Proportional mortality ratio 675,000/1,500,000

x 100 - 45 of total deaths per year from cancer

Measure of Mortality Infant Mortality Rate

- Defined as the number of deaths of persons age

0-1 in a calendar year, divided by the number of

live births in that year, quotient multiplied by

1000 - Example
- State, Yr - live births 325,000 infant deaths

1,750 - Infant mortality 1,750/325,000 x 1000
- 5.4 infant deaths per 1000 live births per year

Measure of Mortality Maternal Mortality Ratio

- Defined as the number of deaths assigned to

puerperal causes (i.e., childbearing) in a

calendar year divided by the number of live

births in that year, the quotient multiplied by

100,000. - Example
- Country, Yr - deaths due to puerperal causes

275 live births 1,750,000. - Maternal mortality ratio 275/1,750,000 x 100,000
- 15.71 maternal deaths per 100,000 live births

per year

Measure of Mortality Neonatal Mortality

Proportion

- Defined as the number of deaths of neonates

(infants divided by number of live births in that year,

the quotient multiplied by 1000 - Example
- State, Yr - deaths at births 325,000
- Neonatal mortality proportion 2,750/325,000 x

1000 - 8.5 neonatal deaths per 1000 live births

Measure of Mortality Fetal Death Ratio

- Defined as the number of fetal deaths in a

calendar years, divided by the number of live

deaths in that year, the quotient multiplied by

1000. - Example
- State, Yr - fetal deaths 2,450 live births

525,000 - Fetal death ratio 2,450/525,000 x 1000
- 4.7 fetal deaths per 1000 live births

Measure of Mortality Perinatal Mortality

Proportion

- Defined as the number of fetal plus neonatal

deaths, divided by the number of live births plus

fetal deaths, the quotient multiplied by 1000 - Example
- State, Yr - fetal deaths 3,250 neonatal deaths

5,750 - live births 475,000
- Perinatal mortality proportion

3,2505,750/475,000 - 3,250 x 1000
- 18.8 perinatal deaths per 1000 fetal deaths

plus live births

Measure of Fertility Crude Birthrate

- Defined as the number of live births in a

calendar year, divided by the population at July

1 of that year, the quotient multiplied by 1000 - Example
- State, Yr - live births 250,000 population

30,000,000 - Crude birthrate 250,000/30,000,000 x 1000
- 8.3 live births per 1000 population per year

Measure of Fertility General Fertility Rate

- Defined as the number of live births in a

calendar year, divided by the number of women

ages 15-44 at midyear, quotient multiplied by

1000 - Example
- Country, Yr - live births 7,500,000 number of

women ages 15-44 35,000,000 - General fertility rate 7,500,000/35,000,000 x

1000 - 214.3 live births per 1000 women ages 15-44

per year

Measure of Morbidity Incidence Rate

- Defined as the number of newly reported cases of

a given disease in a calendar year, divided by

the population on July 1 of that year, the

quotient multiplied by either 1000, 100,000, or

1,000,000 (whatevers convenient). - Example
- State, Yr - new cases of AIDS reported 5,250

population 35,000,000 - Incidence rate 5,250/35,000,000 x 100,000
- 15 new AIDS cases per 100,000

Measure of Morbidity Prevalence Proportion

- Defined as the number of existing cases of a

given disease at a given time, divided by the

population at that time, the quotient multiplied

by 1000, 100,000, or 1,000,000 (whatevers

convenient) - Example
- Country, Yr - number of men alive with AIDS

3,750 population 15,000,000 men - Prevalence proportion 3,750/15,000,000 x 100,000
- 25 AIDS cases per 100,000 men

Measure of Morbidity Case-Fatality Proportion

- Defined as the number of deaths assigned to a

given cause in a certain period, divided by

number of cases of the disease reported during

the same period, the quotient multiplied by 100. - Example
- Country, Yr - report number of male AIDS cases

45,000 deaths from the disease 37,000. - Case-fatality proportion 37,000/45,000 x 100
- 82.2 mortality among reported cases of AIDS

Adjustment of Rates (or, Rate Adjustment)

- Adjusting, or standardizing, rates is used to

make valid comparisons between populations that

may differ in some significant way (i.e., age

distribution). - Standardized rates have no meaning in isolation,

since adjusted rates are artificial. - Depending on type of data - there are two methods

to adjust rates - direct (preferred) and

indirect. - The numerical values of the adjusted rates depend

on the choice of the standard population.