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37 Cards in this Set
- Front
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What is Demography |
Demography is the statistical study of human populations with respect to size, structure, distribution, growth and vital statistics. It is concerned with how populations change in response to fertility, mortality and migration. This helps in making estimates or forecasts about future population size and structure, necessary for healthcare planning. |
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Sources of Population data |
Sources of Population Data These include: Census Vital statistics Sample surveys |
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Census |
Census is periodic head counts or enumeration of the population.It is usually carried out at 10-year intervals.Census data constitute the principal source of denominator data for calculation of mortality 9death) and morbidity (sickness) rates.Accurate population data is necessary for health planning and programming, evaluation and estimation of trends anticipated in future.Census figures are used in allocating resources e.g. funds for health and other programmes. |
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Information obtained from census |
Information obtained from all individuals during census may include name, address, sex, race, marital status, relationship to head of household and some characteristics of housing such as type of residence, tenure, accommodation and facilities. Further information obtained from 20% sample of the population with the help of a longer questionnaire may include nativity, migration, education, party, employment status, income, etc. All information relating to individuals is strictly confidential and is only released in form of summary statistical figures. |
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Methods of enumeration in census |
Methods of Enumeration There are two main methods of enumeration; De facto method, and De jure method |
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Dr Facto Method |
People are counted based on where they are located on the day of enumeration.For instance, a businessman living in Enugu but working in Abuja will be assigned to Abuja on a de facto census.Nigeria uses the de facto method of enumeration |
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Dr Jure method |
De Jure Method People are counted in accordance with their usual place of residence. The businessman living in Enugu but working in Abuja will be counted in Enugu on a de jure census because that is his residential address. |
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Vital statistics |
Vital statistics are obtained from registration of vital events that give information about the health of a population. These are: •Births •Deaths and •Marriages |
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Birth registration |
Identifies an individual as a citizen of a country. Data obtained are used to study the pattern of fertility and make population estimates and projections. Information varies from country to country Used for the issuance of international passports and for school enrolment |
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Death registration |
Carried out by the medical practitioner that attended the person during his last illness. Aim is to state the cause of death Data include name, age, sex, date, time, place of death, immediate cause of death, antecedent causes, etc. Terminologies of the Internal Classification of Disease are used Precision of death certificate decreases as age increases Death certificate is used for death benefits, insurance claims and for statistical purposes. |
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Deaths reportable to a coroner for autopsy |
•When there was no medical attendant during the last illness of deceased •When it is suspected that the person died from unnatural causes such as accidents, homicide, suicide, etc. •When the death occurred before full recovery from a surgical operation or the administration of an anesthetic •When the death occurred within 24 hours of admission into a health facility |
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Marriage registration |
Marriages are registered with the local government council |
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Sample surveys |
In the developing world, where other data sources are scare, surveys of various kinds often present the best source of data on basic demographic parameters. Data quality is much better in a survey than a census because it is more likely that well trained interviewers are used in the former. Examples are: •World Fertility Survey •Demographic and Health Survey Programme These are global survey programmes that are carried out in many countries of the world. The programmes provide data for a range of countries, including many that lack adequate visit registration systems. |
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Sources of health data |
1. Records from health Institutions: Morbidity data about illness and disease are obtained from various types and sections of health institutions Outpatient clinic; Antennal clinic; STD clinic; Infant welfare clinic; Chest clinic; Inpatient; Inpatient records; Autopsy reports; Laboratory reports, etc. Assessment of morbidity patterns within community presents the iceberg phenomenon. Data from hospitals and other orthodox medical institution form the tip of the iceberg. Other sources of health care and subclinical disorders form the larger of larger mass beneath the surface, e.g. Alternative medicine; Self medication; Patent medicine dealers; Quacks; Traditional medical practitioners; Prayer houses, etc. 2. Disease Registers: A disease register is used to identify and record information on people that have been diagnosed with the particular disease in the area covered by the registry New cases are continually being added Cancer registry; Tuberculosis registry; Rheumatoid fever registry; Mental illness registry Periodic reports are published giving detailed incidence, survival and mortality rates. 3. Reports of epidemic investigations: When an epidemic occurs, an investigation is usually carried out to •Verify the diagnosis •Establish the existence of the epidemic •Write the report and •Commence control measures The report is an importance source of heath information4. Other sources of health data: •Health surveys and control programs •Notification of disease |
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What is disease notification |
This is the reporting of the occurrence of a disease to appropriate health authority for the purpose of taking an urgent action to control it. |
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Most important tool for measuring disease |
Morbidity and Mortality rate
Indicates probability or risk of disease in a defined population over a specified period of time Rate = number of events in a specified period/population at risk in a specified period × K |
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Incidence rate |
Incidence rate is a morbidity rate used to measure illness It measures the probability that healthy people will develop an illness during a specified period of time. It indicates the rate at which new disease occurs in a defined, previously disease-free population. Incidence rate = number of new cases of a disease over a period of time/population at risk × K To determine incidence rate, follow a group of people and determine the rate at which new cases of disease appear. Also consider the following: Health status of the population i.e. ‘diseased’ or’ not diseased Time of onset of disease Specify the numerator i.e. number of people or number of condition i.e. number of persons who develop diarrhea or number of diarrheal episodes Specify the denominator Made up of a defined population that is accurately enumerated Mid-point represents average population at risk e.g. mid-year population |
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Prevalence rate |
Prevalence rate measures the number of people in a population who have a disease at given time. Prevalence rate= number of existing cases of a disease at a point in time or during a period or interval/total popilation × K It depends on the number of people that have been ill (previous incidence) and the duration of their illness. P =I x D Chronic illnesses lead to high prevalence Acute illnesses lead to either death or recovery and therefore lower prevalence |
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Differences between incidence and prevalence rates |
•Knowledge of time of onset of disease or illness is not required in a prevalence study •Denominator in prevalence rate is the entire population •Numerator in prevalence rate contains both old and new cases. •Prevalence study is easier and cheaper than incidence study. |
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Uses of incidence and prevalence rates |
•Management of health services •Monitoring and disease control programs •Planning of health services •Manpower needs •Estimating changes in disease pattern over time •Determining the causation of diseases e.g. incidence rate |
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Crude rates |
These are summary rates based on actual number of events (e.g births, deaths) in a total population over a given time. Crude birth rate= no of live births in an area in a year/ average population in the area in the year (ie mid year population) × K Crude death rate= number of deaths in an area in a year/mid year population × K They do not take into consideration the specific subgroups which may exhibit significant differences in rates |
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Specific rates |
Specific rates are used to study and compare population sub-groups. Demographic components like age, sex, race, etc. taken into consideration. Age specific death rate (50-60 years) = Number of deaths among people aged 50-60 years in an area in a year/ ave. population aged 50-60 years in the area in that year × K |
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Adjusted or standardized rate or ratio |
A form of summary rate Takes into consideration a standard population The more stable rates of a larger population are applied to the population of the smaller study group (by simple proportion) to get the expected rates Standardized mortality rate or ratio= Observed deaths in the study population/expected deaths in the study population × K Standardized mortality rate or ratio= Observed illness in the study population/expected illness in the study population × K |
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Types of error |
1. Random error (chance) 2. Systematic error (bias) |
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Sources of error in measurement of disease |
Errors may occur as a result of: 1.Use of non-random samples of the population 2. Non-participation of members of the target population 3. Observer variations: (inter-observer/intra-observer variations) Ways to reduce these: •Standardize diagnostic and clinical methods •Train personnel to carry out procedure and record observation •Use multiple observers 4. Different response pattern : Events that cause embarrassment may be unreported leading to errors. 5. Variation in illness behavior or perceptions of illness 6. Variation in availability of treatment resources |
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Selected indices of health |
•crude death rate •crude birth rate •cause specific death rate •stillbirth rate •perinatal mortality rate •neonatal mortality rate •post neonatal mortality rate •infant mortality rate •under 5 mortality rate •fertility rate •maternal mortality rate •maternal mortality ratio |
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Population dynamics |
The study of short term and long term changes in the size and age composition of populations and the biological and environmental processes influencing those changes |
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Three main causes of population change |
•births: measured using birth rate •deaths: measured using death rates •migration: immigration or emigration |
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Formula for calculating number of individuals at time 1 |
N1 = N0 + (B-D) + (I-E) Where N0= number of individuals at time 0 B= number of individuals born D= number of individuals that died I= number of individuals that immigrated E= number of individuals that emigrated between time 0 & 1 |
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Natural causes of population change |
Births and deaths |
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What is the difference between the birth rate and date rate of a country or place called |
Natural increase The rate of natural increase is given as a percent value, calculated by dividing the natural increase by 10 |
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Demographic transition |
This shows population change over time It studies how birth rate and death rate affect the total population of a country. It is often called the demographic transition model |
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Stages of the demographic transition model |
1. Total population is low but it is balanced due to high birth rates and death rates. 2. Total population rises as death rates fall due to improvements in health care and sanitation. Birth rates remain high. 3. Total population is still rising rapidly. The gap between birth and death rates narrows due to the availability of contraception and fewer children being needed to work due to the mechanization of farming. The natural increase is high. 4. Total population is high, but it is balanced by a low birth rate and a low death rate. Birth control is widely available and there is a desire for smaller families. 5. Total population is high but going into decline due to an ageing population. There is a continued desire for smaller families, with people opting to have children later in life. As a country passes through the demographic transition model, the total population rises. Most LEDCs are at stage 2 or 3 (with a growing population and a high natural increase) Most MEDCs are now at stage 4 of the model and some such as Germany have entered stage 5.
Note: MEDCs are countries which have a high standard of living and a large GDP . LEDCs are countries with a low standard of living and a much lower GDP. |
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Population structure |
•Population structure means the ‘make up’ or composition of a population. •It shows how the population is divided up between males and females of different age groups. •Population structure is usually shown using a population pyramid •A population pyramid shows the structure of a population by comparing relative numbers of people in different age groups. •A population pyramid can be drawn up for any area, from a whole continent or country to an individual town, city or village •Population structures differ marked between less economically developed country (LEDCs) such as Nigeria, Mozambique, India and Afghanistan, and more economically developed countries (MEDCs) such as USA, UK, Sweden and Japan. |
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Analysis of population pyramids |
The keys things to know about population pyramids are as follows: •The shape of a population pyramid can tell a lot about an area’s population. •The shape gives information about birth and death rates as well as life expectancy. •A population pyramid reveals how many dependants there are. •There are two groups of dependants; young dependants (aged below 15) and elderly dependants (aged over 65). • Dependants rely upon the economically active for economic support. •Many LEDCs have a high number of young dependants, whilst many MEDCs have a growing number of elderly dependants |
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How population pyramids change over time |
•A population pyramid that is very triangular (e.g. Mozambique in 2000) shows a population with a high number of young dependants and a low life expectancy. •A population pyramid that has fairly straight sides (more like a barrel) shows a population with a falling birth rate and a rising life expectancy. •Over time, as a country develops, the shape changes from triangular to barrel-like. •Places with an ageing population and a very low birth rate would have a structure that looks a pyramid that is places upside-down. |
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Population growth |
As mentioned before, population numbers change over time, influenced by births, deaths and migration into or out of the area.Global population levels, having grown slowly for most of human history, are now rising.At present the world’s population is growing quickly, though this has not always been the case.Until the 1800s the world’s population grows slowly for thousands of years.In 1820 the world’s population reached one billion.In the early 1970s, the world’s population reached three billionIn 1999, less than 30 years later, the population doubled to six billion.The global rate of population growth is now one billion every 15 years. |
