chapter 15 vital statistics and demographic methods

CHAPTER 15

Vital Statistics and Demographic Methods

OUTLINE

15.1 VITAL STATISTICS AND DEMOGRAPHICS

Points out the importance of vital statistics and demographics 15.2 SOURCES OF VITAL STATISTICS AND DEMOGRAPHIC DATA

Discusses three sources of data – census data, registration of births and deaths, and morbidity data – as the building blocks for computing vital ratios, and proportions

15.3 VITAL STATISTICS RATES, RATIOS, AND PROPORTIONS

Introduces the concepts of rates, ratios, and proportions within the context of vital statistics 15.4 MEASURES OF MORTALITY

Presents a variety of measures, each being a means of measuring the frequency of deaths in a community 15.5 MEASURES OF FERTILITY

Shows two key methods for quantifying fertility that are indispensable in making population estimates 15.6 MEASURES OF MORBIDITY

Describes three of the many measures of illness that exist 15.7 ADJUSTMENT OF RATES

Explains how to make reasonable comparisons between noncomparable populations

LEARNING OBJECTIVES

• • 1. Distinguish among rates, ratios, and proportions, and among

measures of morbidity, mortality, and fertility

• 2. Compute and understand the meaning of various vital measures

• 3. State the reasons measures are adjusted

• 4. Compute an adjusted rate by the direct method•

VITAL STATISTICS AND DEMOGRAPHICS

• • A. Vital statistics are important researchers, epidemiologist, health planners, and

other health professionals to:

– 1. determine the health status of a community

– 2. to decide how best to provide a health service

– 3. to plan a public health program

– 4. to evaluate a program’s effectiveness

• B. Demographic variables describe a population’s characteristics•

SOURCES OF VITAL STATISTICS AND DEMOGRAPHIC DATA

•

• A. Three main sources of vital statistics

– 1. Census

– 2. Registration of vital events

– 3. Morbidity surveys•

THE CENSUS

• • A. United States has conducted a decennial census of population since 1790

• B. Each household and resident is enumerated

• C. Information obtained on each person includes

– 1. gender

– 2. age

– 3. race

– 4. marital status

– 5. place of residence

– 6. relationship to or position as head of household

THE CENSUS

• D. A systematic sample of households then provides the following information

– 1. income

– 2. housing

– 3. number of children born

– 4. education

– 5. employment status

– 6. means of transportation to work

– 7. occupation

THE CENSUS

• E. Census tables are published for

– 1. entire United States

– 2. States

– 3. Metropolitan Statistical Areas (MSA’s)

– 4. counties

– 5. cities

– 6. neighborhoods (census tracts)

– 7. city blocks

THE CENSUS

• F. Decennial Census of the United States

– 1. published 2 years after the census is taken

– 2. made available on magnetic tape for computer analysis

– 3. summarized annually in the Statistical Abstract of the United States

•

ANNUAL REGISTRATION OF VITAL EVENTS

• • A. Vital events are:

– 1. births

– 2. deaths

– 3. marriages

– 4. divorces

• B. State law (United States) requires that all vital events be registered


• C. Birth certificates serve as proof of:– 1. citizenship

– 2. age

– 3. birthplace

– 4. parentage

• D. Death certificates are required as:– 1. burial documents

– 2. settlement of estates and insurance claims

• E. In the United States, death registration– 1. began in Massachusetts in 1857

– 2. extended to 10 states and the District of Columbia and several other cities by 1900

– 3. has been conducted nationwide since 1933


• F. Birth registration– 1. began in 1915 in 10 states and the District of Columbia

– 2. Extended to all states by 1933

• G. Birth Certificate Information– 1. Name

– 2. Sex

– 3. Date and time of birth

– 4. Race of parents

– 5. Birth order

– 6. Occupation of father

– 7. Place of birth

– 8. Residence of mother

– 9. Physician’s (or attendant’s) certification


• H. Death Certificate

– 1. Name– 2. Date and time of death– 3. Race– 4. Age– 5. Place of birth– 6. Names of decedent’s parents– 7. Name and address of survivor (or informant)– 8. Marital status– 9. Occupation– 10. Place of residence– 11. Cause(s) of death– 12. Place of death– 13. Burial data– 14. If death due to injury: accident, suicide, or homicide– 15. Physician’s (or coroner’s) certification


• I. National Center for Health Statistics– 1. collects a systematic sample of 10% of the births and deaths in each state– 2. Publishes the Monthly Vital Statistics Report – 3. issues the four-volume set Vital Statistics of the United States

• J. The National Death Index – a nationwide, computerized index of death records compiled from tapes submitted by the vital statistics offices of each state

• K. Mortality Data– 1. death certificate number– 2. state where the death occurred– 3. date of the death– 4. copies can be ordered from the states vital statistics office

• L. Nosologist – working for the National Center for Health Statistics these individuals perform the task of classifying deaths into various numerical categories using the two current volumes on how to classify a particular cause of death (COD)

•

MORBIDITY SURVEYS

• A. Morbidity Surveys (i.e., data on the prevalence of disease) – data is more difficult to gather than mortality data

• B. Gathering morbidity data

– 1. 1876 – Massachusetts tried voluntary case reporting

– 2. 1883 – Michigan began compulsory reporting

– 3. Still wide gaps in data today

• C. Data flow

– 1. local health departments tally the number of cases of reportable communicable disease within its area and forwards its count to the

– 2. state health department, where a cumulative total is made and sent to

– 3. the Centers for Disease Control in Atlanta for publication in Morbidity and Mortality Weekly Reports (MMWR)

MORBIDITY SURVEYS

• D. Alternative methods of gathering estimated of morbidity data

– 1. Reportable diseases

– 2. National Health Survey

– 3. Hospital records data

– 4. Industrial hygiene records

– 5. School Nurse records

– 6. Medical care subgroups (most often: prepaid medical plans)

– 7. Chronic-disease registries (most often: tumor registries)

– 8. Insurance industry data

MORBIDITY SURVEYS

• E. National Health Survey

– 1. Originated by an Act of Congress in 1956

– 2. Provides for an annual nationwide survey of a representative sample of 40,000 persons

– 3. Subprograms• a. National Health Interview Survey• b. National Health and Nutrition Examination Survey (HANES)• c. National Hospital Discharge Survey• d. National Ambulatory Medical Care Survey• e. National Nursing Home Survey

– 4. Results are published in the Vital and Health Statistics sometimes referred to as the “rainbow series”

– 5. Published medical care data results include:• a. incidence• b. prevalence rates for many diseases• c. length of hospital stays• d. hospitalizations by cause• e. number of days of disability• f. patterns of ambulatory care service

MORBIDITY SURVEYS

• F. Professional Activity Study of Battle Creek, Michigan– 1. uniform reporting system used by over 2000 hospitals nationwide– 2. used by researchers to make morbidity estimates for population studies– 3. Hospital administrators use it for planning strategies of health care delivery

• G. Chronic-disease registries– 1. most are cancer related (therefore know as cancer or tumor registries) defined as a

“facility for the collection, storage, analysis, and interpretation of data on persons with cancer

– 2. Other registries• a. cardiovascular disease• b. tuberculosis• c. diabetes• d. psychiatric disease

– 3. Registry types• a. hospital-based – they work within the walls of a hospital or group of hospitals• b. population-based – they serve a population of defined composition and size

• H. Demographic Yearbook (United Nations 1990) – source for similar data for most of the developed world published annually

•

VITAL STATISTICS RATES, RATIOS, AND PROPORTIONS

A. Rate – is an expression where

– 1. a = the number of persons experiencing a particular event during a given period

– 2. a + b = the number of persons who are at risk of experiencing the particular event during the same period

– 3. t = the total time at risk

– 4. c = a multiplier, such as 100, 1000, 10,000, or 100,000

– 5. The purpose of the multiplier, or base, is to avoid the inconvenience of working with minute decimal fractions

ctba

a


• 6. Three kinds of rates

– a. Crude Rates• i. computed for an entire population

• ii. disregard differences that usually exist by age, sex, race, or some category of disease

– b. Specific Rates• i. consider the differences among subgroups consider the differences

• ii. computed by age, race, sex, or some other variable

– c. Adjusted (or standardized) Rates – used to make valid summary comparisons between two or more groups

possessing different age (or other) distributions


B. Ratio – is a computation of the form where

1. a and c are defined as rates

2. d is the number of individuals experiencing some event different from event a during the same period

C. Proportion – is an expression of the form

where

a, a + b, and c are defined for rates

cd

a

cba

a

MEASURES OF MORTALITY

A. Each rate is a measure of the relative frequency of deaths that occurred in a given population over a specific period

B. Mortality Rate – must know the population and time at risk to compute the mortality rate

ANNUAL CRUDE DEATH RATE

A. Defined as the number of deaths in a calendar year divided by the population on July 1 of that year, with the quotient multiplied by 1000

B. Universally used

C. A generalized indicator of the health of a population

AGE-SPECIFIC DEATH RATE

A. 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, with the quotient multiplied by 1000

CAUSE-SPECIFIC DEATH RATE

A. Defined as the number of deaths assigned to a specific cause in a calendar year divided by the population on July 1 of that year, with the quotient multiplied by 100,000

CAUSE- /RACE SPECIFIC DEATH RATE

A. One of many possible examples of how the idea of specific death rates may be extended simultaneously to cover two characteristics

PROPORTIONAL MORTALITY RATE

A. 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, with the quotient multiplied by 100

MATERNAL MORBIDITY RATIO

A. Defined as the number of deaths assigned to puerperal causes (i.e. related to childbearing) in a calendar year divided by the number of live births in that year, with the quotient multiplied by 100,000

INFANT MORBIDITY RATE

A. Defined as the number of deaths of persons of age 0-1 in a calendar year divided by the number of live births in that year, with the quotient multiplied by 1000

NEONATAL MORTALITY PROPORTION

• • A. Defined as the number of deaths of neonates

• (i.e., infants less than 28 days of age) that occurred in a calendar year divided by the number of live births in that year, with the quotient multiplied by 1000

•

FETAL DEATH RATIO

A. Fetal death is defined as the delivery of a fetus that shows no evidence of life (no heart action, breathing, or movement of voluntary muscles) if the 20th week of gestation has been completed or if the period of gestation was unstated

B. Fetal death ration is defined as the number of fetal deaths in a calendar year divided by the number of live births in that year, with the quotient multiplied by 1000. Note that this ratio only applies to fetal deaths that occur in the second half of pregnancy. No reporting is required for early miscarriages

PERINATAL MORTALITY PROPORTION

A. Defined as the number of fetal plus neonatal deaths divided by the number of live births plus fetal deaths, with the quotient multiplied by 1000

MEASURES OF FERTILITY

A. Indispensable for approaching population control problems

B. Particularly useful in planning maternal and child health services

C. Help school boards plan for future needs for facilities and teachers

CRUDE BIRTHRATE

A. Defined as the number of live births in a calendar year divided by the population on July 1 of that year, with the quotient multiplied by 1000

B. Non-too-sensitive measure as the population (denominator) includes both men and women

GENERAL FERTILITY RATE

A. Defined as the number of live births in a calendar year divided by the number of women ages 15-44 at midyear, with the quotient multiplied by 1000

MEASURES 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, with the quotient multiplied by a convenient factor, usually, 1000, 100,000, or 1,000,000

PREVALENCE PROPORTION

Defined as the number of existing cases of a given disease at a given time divided by the population at that time, with the quotient multiplied by 1000, 100,000, or 1,000,000

CASE-FATALITY PROPORTION

Defined as the number of deaths assigned to a given cause in a certain period by the number of cases of the disease reported during the same period, with the quotient multiplied by 100

ADJUSTMENT OF RATES

A. Adjusted rates are artificial

B. Do not reflect the actual rates of a population

THE DIRECT METHOD

A. Applies a standard population distribution to the death rates of two comparison groups

B. Sum of the expected deaths for the two groups is then used to compute the adjusted death rate (dividing the expected deaths by the total of the standard population)

C. Essential to have bot the age-specific death rates for the populations being adjusted and the distribution of the standard population by age (or by whatever other factor is being adjusted)

D. U.S. Standard Million – a population of 1 million persons that identically follows the age distribution for the entire United States

THE INDIRECT METHOD

A. Utilized when age-specific death rates are not available for the populations being adjusted but the age-specific death rates for the standard population are known

B. We compute a Standard Mortality Ration (SMR) (i.e., observed deaths divided by expected deaths) and use it

as a standardizing factor to adjust the crude death rates of given populations

C. The SMR increases or decreases a crude rate in relation to the excess of deficit of the group’s composition as compared to the standard population

CONCLUSION

Public health decision making is a quantitative matter. The health of a population is assessed by use of its vital statistics and demographic data. Information about demographic characteristics is obtainable from census data, registration of vital events, and morbidity surveys. Such data are used to calculate vital rates and other statistics that are used to indicate the magnitude of heath problems.

Vital rates, ratios, and proportions are classified into measures of mortality (death), fertility (birth), and morbidity (illness). These measures may be crude or specific, the latter referring to calculations for subgroups selected for a common characteristic such as age, sex, race, or disease experience. Comparisons of vital rates, ratios, and proportions among different populations should be made with care and be validated by use if specific or adjusted measures. The choice of the adjustment method depends on the type of data available.

chapter 15 vital statistics and demographic methods

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