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Glossary of Population / Health Terms |
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Acute Disease: A disease of rapid onset and usually of brief duration. The term carries no connotations about the severity of a disease. (Compare with chronic disease.) Age-Dependency Ratio: The ratio of persons in the ages defined as dependent (usually taken as under 15 and 65+) to those in the ages defined as economically productive (15 / 64 years) in a population. This ratio is sometimes broken down into Youth Dependency Ratio (<15 / 15-64 years) and Aged Dependency Ratio (65+ -15-64) components. Age-Sex Structure (Composition): The number or percentage of people in a population distributed by age and sex. Arboviral Disease: A viral disease transmitted by arthropods (i.e. arthropod-borne). There are over 100 arboviruses that affect humans, mosquitoes being the most common vector. Dengue and yellow fever are the most serious and widespread arboviral diseases. The main arboviral disease in Australia is Ross River Fever. Cancer: A group of diseases involving body cells multiplying out of control to form masses of tissue (tumours) that damage the area around them. Cancer cells frequently metastasise, that is, spread to and invade and damage other parts of the body. Cancers are termed malignant neoplasms (tumours) and comprise ICD-9 Codes 140-208. ICD-10 Codes C00-C97. Cardiovascular Disease: Any disease of the heart or blood vessels (e.g. stroke, ischaemic heart disease, peripheral vascular disease). The major cause of death in developed countries. Also referred to as circulatory disease. ICD-9 Codes 390-459. ICD-10 Codes I00-I99. Carrying Capacity: The size of population that could theoretically be supported indefinitely under given environmental conditions. This population size will vary according to lifestyle, level of living and type of economy considerations. Case Fatality Rate: The proportion of persons contracting a disease who die from the disease. The rate is a measure of the virulence ('killing power') of the disease. Cause of Death: Deaths are categorised according to the World Health Organisation's International Classification of Diseases, Injuries and Causes of Death. The cause of death in this classification is defined as the underlying cause, that is, the disease or injury which initiated the train of morbid events leading directly to death. The underlying cause may be different from the immediate cause. For example, the underlying cause of death of a person who fell and broke a hip and then went on to develop and die of pneumonia in hospital would be the fall. The immediate cause would be pneumonia. The current version of the International Classification is the 10th Revision (ICD-10) and has been used to classify all deaths registered in Australia from 1 January 1999. From 1979-1998 the ICD-9 classification was used. Census: A count of the entire population in a given area at a particular time. Some national censuses however, include sampling. For example, a short census form canvassing key social and demographic information may used for the total population and a longer form asking extra questions may be distributed to just a sample of households. Cerebrovascular Disease: Abnormal condition of the blood vessels of the brain resulting in impairment of blood and oxygen flow to the brain. Interference to the circulation due to bleeding from a weakened artery (cerebral haemorrhage) or blockage of an artery (cerebral thrombosis and cerebral embolism) is known as a stroke. ICD-9 Codes 430-438. ICD-10 Codes I60-I69. Child-Woman Ratio: The number of children aged 0-4 divided by the number of women of childbearing age (usually taken as 15-44, but sometimes 15-49), and normally expressed as per 1,000. A measure of fertility not requiring births data. Chronic Disease: A disease that persists for a long time. The term carries no connotations about the severity of a disease. (Compare with acute disease.) Circulation: Geographical mobility that is short-term and repetitive or cyclical that does not result in a permanent change of residence. Examples are the journey to work, seasonal labour movements and transhumance. Closed Population: A population that has no migratory flows in or out and thus whose size can only change through births and deaths. The concept is sometimes used in making population projections (i.e. a no migration scenario). Cluster: An unusual aggregation of adverse health events (e.g. childhood leukaemias, birth defects, youth suicides, drug overdoses) that are grouped together in time and space. Cohort: A group of persons who experience a certain event (e.g. birth, marriage) during a defined time period. Cohort Analysis: The analysis of the demographic behaviour (e.g. getting married, having children, dying) of a cohort of people over time. For example, the fertility rates of women born in 1920, 1950 and 1970 (i.e. the 1920, 1950 and 1970 birth cohorts) could be compared as they progressed through their childbearing years. (Compare with period analysis.) Co-morbidity: When a person has two or more health problems at the same time. Completed Fertility: The average number of children born per woman to a cohort of women by the end of their reproductive years. Also referred to as lifetime fertility. A useful measure for comparing the fertility levels of different generations of women. Contraception: Methods used by individuals or couples to prevent conception resulting from sexual intercourse. Contraceptive Prevalence: The proportion of married women of reproductive age using a contraceptive method. Crude Birth Rate: The number of live births in a specified period (usually one year) divided by the average total population in that period (usually taken as the mid-year population). The rate is normally expressed per 1,000 population. Crude Death Rate: The number of deaths in a specified period (usually one year) divided by the average total population in that period (usually taken as the mid-year population). The rate is normally expressed per 1,000 population.
Crude
Rates:
Any
rate
based
on
the
number
of
events
(e.g.
births,
deaths,
marriages)
in
a
total
population
over
a
specified
period.
De Facto Population: The population actually in a given area at the time of a census. The majority of Australian census statistics are tabulated on this place of enumeration basis. (Compare with de jure population.) Degenerative Disease: A disease that involves the biological deterioration of the body (e.g. heart disease, stroke), usually associated with ageing. De Jure Population: The population usually resident within an area, regardless of whether or not they were there at the time of the census. One of the census community profiles produced by the Australian Bureau of Statistics is based on place of usual residence. (Compare with de facto population.) Demographic Balancing Equation: A formula showing that the population of an area at the end of a given period is equal to the population at the start of the period plus the births, minus the deaths, plus the in-migration and minus the out-migration that occurred during the period. Demographic Transition: The long-term shift of birth and death rates from high to low levels in a population. The decline in mortality normally occurs first, leading to a period of rapid population growth before fertility starts to fall. Some writers prefer to term this process the Vital Transition, using Demographic Transition as more of an umbrella concept covering transitions on a variety of demographic dimensions besides fertility and mortality (e.g. in age structure, mobility, population distribution). Demography: The scientific study of human populations. The field covers three main areas: (1) the size, growth, distribution and composition of populations; (2) the demographic processes (fertility, mortality and migration) which directly influence population size, growth, distribution and composition; (3) the relationships between these elements and processes and the environments (e.g. social, economic, political, cultural, technological, biophysical) within which they exist. Differential Fertility: The differences in fertility between various subgroups of the population (e.g. age, ethnic, income, education, religious, place of residence groups) at a particular time or within or between specific cohorts. Differential Mortality: The differences in mortality between various subgroups of the population (e.g. age, ethnic, occupational, place of residence groups) at a particular time or within or between different cohorts. Disability-Adjusted Life Years (DALYs): The years of life lost to premature mortality and years lived with a disability, adjusted for the severity of the disability. One DALY is one lost year of healthy life. The DALY thus gives a wider picture of health problems (disease burden) than mortality statistics portray through incorporating the nonfatal consequences of ill-health and injuries. Doubling Time: The number of years it would take for a population to double its current size under a specified constant rate of growth. The time can be calculated by dividing the number 69.3 by the annual percentage growth rate. For example, a constant annual 2% rate of growth would see a population double in 34.65 years. Ecological Footprint: The total area of land and water required to produce the resources for and absorb the waste from a given population. Emigrant: A person who migrates from one country to settle in another. Endemic Disease: The normal level of disease which is permanently present in a population. Epidemic: A mass outbreak of a disease in a particular geographic area which spreads and then disappears relatively quickly. Epidemiologic Transition: The shift in the major causes of death from infectious diseases (e.g. tuberculosis, diarrhoea and enteritis, pneumonia) to chronic and degenerative ailments (e.g. heart disease, stroke, cancer) associated with the long-term decline in mortality from high to low levels. Epidemiology: The study of the patterns and determinants of health and disease in populations. Ethnicity: Refers to the classification of people into groups on the basis of a common attribute such as national origin, ancestry, language, religion, or race. While all members of a population can be classified on these attributes the term ethnic group is most often used with respect to minority groups.
Exponential
Population
Growth
Rate:
A
growth
rate
where
a
population
is
continuously
increasing
(or
decreasing)
at
a
constant
rate.
Sometimes
the
term
exponential
is
incorrectly
used
to
denote
very
fast
growth.
However,
exponential
growth
can
be
slow,
or
even
negative.
Family:
Two
or
more
persons
living
together
who
are
related
by
birth,
marriage,
or
adoption.
Fecundity: The physiological capacity of a woman or man to reproduce. This capacity may or may not lead to fertility (live births). Fertility: The actual reproductive performance of individuals, couples, groups or populations. The occurrence of live births in a population. One of the three basic demographic processes (along with mortality and migration). Also referred to as natality.
Fetal
Death
(Stillbirth):
In
Australia,
the
birth
of
a
child
weighing
at
least
400
grams
(or,
where
birthweight
is
unknown,
gestation
of
at
least
20
weeks)
who
shows
no
sign
of
life.
General Fertility Rate: The number of live births per 1,000 women aged 15-44 (or 15-49) in a specified period. Geometric Population Growth Rate: A growth rate compounded at the end of a fixed interval (e.g. quarterly, annually). Geometric growth differs from exponential growth in that the latter compounds continuously. Gross Reproduction Rate: The average number of daughters that would be born to a woman if she passed through her childbearing years experiencing the age-specific fertility rates of a given period. Health Transition: The changes over time in a society's health. The term has a wider meaning than mortality transition, covering the positive condition of health as well as death and illness. It also refers to the cultural, social and behavioural determinants of health.
Household:
One
or
more
persons
who
usually
reside
in
the
same
dwelling
who
make
common
provision
for
food
and
other
essentials
for
living.
Immigrant: A person who enters one country from another to take up permanent residence. Immunisation (Vaccination): The production of immunity to infectious disease artificially by introducing specific antigens (dead or weakened microorganisms) into the body. The body produces antibodies in response to the antigens, giving protection from that disease. Incidence Rate: The number of new cases of a disease (or injury or other health-related condition) over a given period in a defined population, divided by the population at risk of contracting the disease. The population at risk is usually taken as the mid-period population. Theoretically, persons who have already got the disease should be excluded from the at risk population, but that is often not possible. Incidence data are valuable in investigations of disease aetiology (causes). Infant Mortality: The death of a child before its first birthday. The infant mortality rate is expressed as the number of infant deaths per 1,000 live births over a specified period. Infectious (Communicable) Disease: Those diseases caused by pathogens (e.g. bacteria, viruses, protozoa, endoparasites). Infectious diseases which are spread by direct contact with infected persons are termed contagious (e.g. sexually transmitted diseases, ebola), although some writers use contagious more loosely as a synonym for all infectious diseases. Intermediate Fertility Variables: The physiological and behavioural factors which directly influence fertility: intercourse variables, conception variables, and gestation variables. Social, economic, cultural, political and other factors which indirectly influence fertility work through the intermediate variables. Also referred to as the proximate determinants of fertility. Internal Migration: Migration within a country. International Classification of Diseases (ICD): The World Health Organisation's Classification of Diseases, Injuries and Causes of Death. The current version is ICD-10, the 10th Revision. International (External) Migration: Migration between countries. Migration into a country is referred to as immigration, and migration from a country as emigration. Ischaemic Heart Disease: Heart disease resulting from reduced blood supply to the heart due to thickening and hardening (atherosclerosis) of the coronary arteries. Causes chest pain (angina) and heart attack. Also known as coronary heart disease. ICD-9 Codes 410-414. ICD-10 Codes I20-I25. Life Expectancy: The average number of additional years a person of a given age and sex would live if current mortality trends were to continue.
Life
Table:
A
table
detailing
the
life
expectancy
and
probability
of
dying
at
each
age
for
a
given
population.
Malthusianism: The belief that population tends to increase faster than the means of subsistence (i.e. food supply, resources) and that population growth therefore must be slowed either by controlling fertility (preventive checks) or by disease, famine or war (positive checks). The term is named after Thomas Malthus, an English clergyman and economist, who propounded this argument in his Essay on the Principle of Population (1798). Note, Malthus was opposed to birth control as a means of slowing population growth, terming the practice a 'vice'. In his view, 'moral restraint' (late marriage and remaining chaste before marriage) was the only acceptable way of restricting fertility. Marital Fertility Rate: The number of live births per 1,000 married women aged 15-44 (or 15-49) in a specified period. Median: The value of a variable above and below which one half of the individuals in the distribution lie. Median Age: The age which divides a population into two equal sized groups; half the members of the population are younger than this age, and half are older. Mean Age: The average (arithmetic mean) age of the members of a population. Migration: A move across some migration defining boundary (e.g. between local government areas, counties, states, countries) involving a permanent change of usual residence. One of the three basic demographic processes (along with fertility and mortality). Mobility: The geographic movement of people, ranging from daily circular movements through to once in a lifetime intercontinental migratory moves. Morbidity: The levels of disease, illness, injuries and disabilities in a population. Measured by such things as health surveys, doctor visits, hospital admissions, disease registers. Mortality: The occurrence of deaths in a population. One of the three basic demographic processes (along with fertility and migration). Mortality Crisis: A sudden large increase in the death rate. Multiple Causes of Death Statistics: In many cases deaths involve several causes and conditions. Until recently causes of death statistics were tabulated on the basis of each death being assigned to a single underlying cause, all other information provided on the death certificate being 'lost'. Processing all causes and conditions reported on each death certificate gives a far more accurate summary of the mortality pattern of a population. Since 1997 Australia has used a US developed Automated Coding System (ACS) to produce multiple causes of death statistics (i.e. both underlying and associated causes). Natality: Births as a component of overall population change. The term is often used interchangeably with fertility. Natural Fertility: A term used to describe the fertility of populations where couples do not alter their reproductive behaviour according to the number of children already born. In other words, couples do not make extra efforts to reduce fertility once they reach a given family size. In essence the term thus refers to fertility levels where no effective form of birth control is practised. Natural Increase/Decrease: The difference between the number of births in a population and the number of deaths over a given period. Neo-Malthusianism: A doctrine based on Thomas Malthus' thesis that population tends to to increase faster than the means of subsistence (i.e. food supply, resources) and therefore needs to be controlled but which, unlike Malthus, advocates the use of contraception and abortion. Neonatal Death: The death of a live-born infant within 28 days of birth. Deaths in the first 7 days of life are termed early neonatal deaths. Deaths between 28 days to one year are called post-neonatal deaths. Net Migration: The difference between the number of in-migrants and out-migrants. Net Reproduction Rate: The average number of daughters that would be born to a woman if she passed through her lifetime experiencing the age-specific fertility and mortality rates of a given period. A NRR of one indicates replacement level fertility, that is, each generation of women is having exactly enough daughters to replace itself in the population.
Nuptiality:
The
frequency,
characteristics
and
dissolution
of
marriages
in
a
population.
Optimum Population: The 'best' population for an area. A problematic concept as different criteria (e.g. economic, social, political, ecological) will likely suggest different optima. For example, the economic optimum population for Australia may be quite large so as to maximise economies of scale and production per capita. The ecological optimum on the other hand, which would emphasise sustainability, would be considerably smaller. Combining these different criteria into a widely agreed upon multidimensional optimum is highly unlikely. Overcount: Overcounting the number of people or events in a census or vital registration system. For example, in censuses accidental double counting may occur of people who have more than one residence or were in transit on census night. Overcounting of vital events meanwhile can occur through such things as the inclusion of events to non-residents or inadvertent double entry of registrations. Overpopulation: The situation where an area's population exceeds the area's carrying capacity. Pandemic: An epidemic that spreads over a very wide area (e.g. the 1918-19 Spanish Flu, the mid-fourteenth century bubonic plague outbreak across Europe). Parity: The number of children previously born alive to a woman. For instance, women who have had three children are referred to as 'three-parity women' and women who have had no children are termed 'zero-parity women'. Perinatal Death: A fetal or neonatal death. Period Analysis: The analysis of demographic events (e.g. fertility, mortality, migration) occurring in a given period of time. These measures give a cross-sectional snapshot of the phenomenon being studied. For example, examining the 1996 infant mortality rates for the various local government areas in Sydney would be a period analysis. (Compare with cohort analysis.) Population Ageing: An increase in the proportion of elderly persons in a population, usually resulting in a rise in the median age. Population Density: The number of people per unit area; for example, persons per square kilometre. Population Dynamics: The three demographic processes (i.e. fertility, mortality and migration) and the changes they bring about in population size, growth, distribution and composition. Population Forecast: A prediction of what the population size (and perhaps distribution and composition) will be at some future date. (Also see population projection.)
Population
Momentum:
The
continued
increase
(or
decrease)
in
population
size
that
would
occur
if
fertility
immediately
changed
to
replacement
level.
The
momentum
occurs
because
of
the
existing
age
structure.
For
example,
zero
population
growth
does
not
occur
immediately
a
NRR
of
one
is
reached
due
to
the
comparatively
high
concentration
of
people
in
the
childbearing
and
pre-childbearing
years
in
populations
that
have
previously
had
above
replacement
fertility.
Momentum
is
thus
built
in
to
the
current
age
structure.
For
example,
if
world
fertility
was
to
drop
to
replacement
level
immediately
and
remain
at
that
level
the
relatively
youthful
present
age
structure
would
cause
population
to
continue
to
increase
for
about
60
years.
Population Policy: Measures taken by a government explicitly designed to influence population size, growth, distribution, or composition. Note, non-demographic policies can also have population effects and thus may act as implicit policies. Government taxation policy, for instance, may make it easier or more difficult for couples to have children (e.g. depending on whether child care costs are tax deductible or not). Population Projection: A computation of future developments in population numbers given specified assumptions about future trends in fertility, mortality and migration. Projections are "what if" statements – that is, what the population would be if the assumed trends occurred. Projections are not forecasts. Population Pyramid: A vertical bar graph showing the distribution of people in a population by age and sex. Males are conventionally plotted on the left side of the graph, females on the right. Population Register: A data collection system in which the demographic details (birth, marriage, migration, death) and some socio-economic characteristics of a population are continuously recorded. Registers covering all individuals in a population are termed universal registers. The Netherlands, Sweden, Norway, Denmark, Finland, Israel and Japan are examples of countries that operate such registers for demographic purposes. In some other countries partial registers limited to specific groups are kept for administrative purposes, such as social security and Medicare. Population Structure (Composition): The distribution of people in a population according to designated demographic traits (e.g. age, sex, country of birth, marital status). Population Younging: An increase in the proportion of young persons in a population, usually resulting in a fall in the median age. Positive Checks: A term introduced by Thomas Malthus (1766-1834) in his Essay on the Principle of Population (1798) to cover the forces for high mortality (disease, famine, war) he argued would emerge if population growth was not restrained by controlling fertility (i.e. preventive checks). Post Enumeration Survey: A survey carried out several weeks after a census to check the coverage and accuracy of the census enumeration. Potential Years of Life Lost (PYLL): A measure of premature mortality. For example, at current average life expectancy levels in developed countries all deaths before age 75 might be considered untimely and to involve a loss of potential years of life. Thus, from this perspective, a person dying on his/her 40th birthday loses 35 potential years of life. Premature Mortality: Deaths that can be considered to have occurred before their due time. This concept underlies the potential years of life lost (PYLL) measure of mortality. Prevalence Rate: The number of people in a defined population with a disease (or injury or other health-related condition) at a given point in time (point prevalence) or during a specified period (period prevalence), divided by the average population. Prevalence data hence show the magnitude of a given health problem and are important in planning services and allocating resources. As they however include persons who may have contracted the disease many years ago, they are not useful in aetiological (causal) studies. Preventive Checks: A term introduced by Thomas Malthus (1766-1834) in his Essay on the Principle of Population (1798) referring to measures to control fertility. While the term covered all methods of fertility limitation, in Malthus' view the only acceptable preventive means was 'moral restraint' (i.e. postponement of marriage and remaining chaste before marriage). Pronatalism: A doctrine or policy which aims to increase the fertility rate in a population.
Proximate
Determinants
of
Fertility:
A
renaming
of
the
intermediate
fertility
variables,
that
is,
the
physiological
and
behavioural
factors
which
directly
influence
fertility.
Four
such
variables
are
seen
as
having
the
greatest
impact
on
fertility:
proportions
married,
postpartum
infecundability,
use
of
contraception,
and
the
extent
of
induced
abortion.
Rate: A measure of the frequency of an event (e.g. births, deaths, migration) in a given population over a specified period of time. Rates are usually expressed per 1,000, 10,000 or 100,000 population, depending on the frequency of event under study, to avoid small decimal numbers. For instance, if 12 people out of a population of 1,600 die in a year the rate is 0.0075 per person, but to make the rate more readily understandable this would normally be expressed as 7.5 per 1,000. Sometimes the term rate is also used more loosely to refer to the ratio between a subpopulation and the total; for example, the unemployment rate – i.e. the number of unemployed persons relative to the total labour force. Rate of Natural Increase/Decrease: The rate at which a population increases or decreases through the surplus (or deficit) of births over deaths during a given period. The rate is expressed as a percentage of the population at the start of the given period. In situations where net migration is zero, the rate of natural increase is the same as the rate of population growth. Rate of Population Growth: The rate at which a population increases or decreases due to the combined impact of births, deaths and migration during a given period. The rate is expressed as a percentage of the population at the start of the given period. Ratio: The result of dividing one number by another number; for example, the sex ratio – i.e. the number of males per 100 females. A ratio in which the numerator is part of the denominator is called a proportion; for instance, the proportion of all deaths that were due to heart disease. Multiplying a proportion by 100 turns the figure into a percentage. Relative Risk: A measure of the proportionate increase in disease rates among people exposed to a particular health risk factor compared with those not exposed to the factor; for example, the relative risk smokers have of developing lung cancer compared with non-smokers. Relative risk is expressed as the ratio of the incidence rate of those exposed to a factor to the incidence rate of those not exposed. Replacement Level Fertility: The level of fertility at which a cohort of women are just replacing themselves with daughters in a population. This is indicated by a Net Reproduction Rate of one. Replacement level fertility is also sometimes expressed in terms of the Total Fertility Rate. In low mortality countries such as Australia a total fertility rate of 2.1 is considered to be replacement level. Return Migration: Migration in which a person returns to live in a previous area of residence. Sampling: The collection of data from just part of a population, often with the purpose of making inferences about the whole population from the sample results – e.g. the five yearly Australian National Health Survey. Some national censuses include a sampling component. Sex Ratio: The ratio of the number of males to the number of females in a population. Usually expressed as the number of males per 100 females. Significance Test: A statistical test to show the probability of whether an observed value (e.g. a standardised death rate) is a chance result. Specific Rates: Any rate that is computed for specific subgroups (e.g. age, sex, race) of a population; for example, age-specific fertility, race-specific mortality. Rates can be made specific for multiple attributes (e.g. age and sex; age, sex and race). By using specific rates the possible confounding effects of age, sex, race, etc. masked in crude rates are eliminated. Stable Population: A closed population with fixed rates of fertility and mortality over a long period and, as a result, an unchanging age-sex structure. Standardised (Adjusted) Rates: These are overall summary rates which (unlike crude rates) are unaffected by compositional differences between the populations being compared. Age is the most common factor standardised for in population research, although it is frequently also necessary to adjust for sex and race, singly or in combination. In comparing mortality variations between areas for instance, other things being equal, areas with younger populations will have lower crude death rates than areas with older populations. Standardisation procedures allow this age structure effect to be controlled. Stationary Population: A special case of a stable population, namely one in which the annual number of births equals the number of deaths, thus producing a zero growth rate.
Survival
Ratio:
The
proportion
of
persons
in
a
population
(or
subgroup)
at
the
beginning
of
a
period
who
are
still
alive
at
the
end
of
the
period.
Total Fertility Rate: The average number of children a woman would have during her lifetime if she were to go through her reproductive years experiencing the age-specific fertility rates of a particular period. The Australian TFR for 1998-99 (1.74) thus indicates the average number of children Australian women would have if, at every age, they had children at the same rate as women did in 1998-99. Undercount: The failure to count all the persons or events which should be counted in a census or vital statistics registration system. Census undercount (underenumeration) may occur due to persons not wishing to be included (even though it is a legal requirement in virtually all countries) or through the difficulty of tracking down people in some areas. Estimates of census undercount are normally made through a post enumeration survey. Birth, death and marriage undercounts occur due to inadequate registration systems. Underlying Cause of Death: This is the precipitating cause of death and is defined by the World Health Organisation as 'the disease or injury which initiated the train of morbid events leading directly |
