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by Dr PHUA Kai Lit
School of Medicine and Health Sciences
Monash University Sunway Campus
Bandar Sunway, Malaysia

Read article on the Eugenics Movement


Demography: Scientific study of population

a. Composition: ethnic, sex, age

b. Distribution: rural, urban, suburban

c. Growth: rapid, slow, decline?

Population is affected by fertility, mortality and migration rates

Final population = Initial population + (Births-Deaths) + (Immigration-Emigration)


Depicted by the Population Pyramid

"Young" population --- pyramid is triangular
"Ageing" population -- pyramid becomes more rectangular

Young population
% under age 15 is high. Due to high fertility.

Ageing population
Elderly rises from about 5% of the total population to more than 20%
Due to low fertility e.g. Japan, Singapore

Median age rises
In rapidly growing populations, the median age can be as low
as 15 or 16. In ageing populations, it rises to 30+

The young-old (65-80 years old) and the old-old (> 80 years old)
The elderly can be divided into the "young-old" and the "old-old".
The old-old have more health problems and use more health resources.

More and more elderly women
This is because women tend to live longer than men.
Therefore, an ageing population will have more and more elderly women.

Elderly people supporting their even more elderly parents

More chronic and degenerative diseases

Multiple health problems are common in the elderly

Demographic Transition Theory

Explain change from high (birth and death) rates to low (birth and death rates). Death rates drop before birth rates. Therefore, rapid population growth for a while.

Falling birth rates due to social and economic changes

e.g. women stay in school longer
more women work outside the home
women marry later
women postpone childbearing
people choose to have fewer kids


Fecundity - biological ability to have kids
Fertility - actual childbearing

Fertility is measured by Crude Birth Rate, Total Fertility Rate etc.

Fertility is affected by:
public policy e.g. some governments attempt to reduce the birth rate while others attempt to increase it
culture e.g. Catholic countries have higher birth rates
economics e.g. urban people have fewer children than rural people
technology e.g. the contraceptive pill has resulted in easier fertility control

Fertility Control:
Includes induced abortion
Unsterile, poorly performed abortions increase maternal mortality (haemorrhage, infection, uterine perforation)

Use of condoms reduce transmission of STDs e.g. HIV/AIDS
Monogamous women at risk of being infected by husbands and boyfriends.

STDs such as gonorrhea can lead to infertility in women

High fertility can affect the health of mother and child
High fertility is a risk factor for maternal mortality in poor countries

Low Birth Weight (<2,500g)
Closely spaced births (<18 months apart) can increase the risk of low birth weight babies

Other issues: Assisted Reproduction
Infertility means inability to conceive children
Possible solutions: adoption, second spouse (in some societies), divorce or even abandonment in other societies, assisted reproduction

Ethical issues associated with assisted reproduction e.g. surrogate motherhood, sperm donors/sperm banks

Sex selective abortion

German IVF (in vitro fertilisation) research affected by Nazi past


Epidemiological Transition
Change in pattern of disease from mostly infectious diseases to mostly chronic and degenerative diseases (cancer, heart disease, stroke, "accidents", suicide, HIV, diabetes, etc)

HIV/AIDS is especially serious in sub-Saharan Africa with high infection and death rates. Some consequences: large numbers of AIDS orphans, many people of working age dying (including healthcare personnel) etc.

Measures of Mortality

Infant Mortality Rate (deaths of babies <1 year old):

Number of Deaths of Infants Under Age 1   X    1,000
Total Live Births
      e.g. Malaysia's IMR in 1995 was 10.4 per thousand live births

Neonatal Mortality Rate (deaths of babies <28 days after birth)

Post Neonatal Mortality Rate (deaths of babies between 28 days to 1 year old)

*NOTE: Infant Mortality Rate = Neonatal Mortality Rate + Post Neonatal Mortality Rate

*NOTE: Low Birth Weight babies (babies who weigh less than 2.5 kg at birth) are at higher risk of dying during the first year of life)

Other Important Measures:

Under 5 mortality rate

Life Expectancy at Birth

Age-specific mortality rates

Cause-specific mortality rates

Maternal mortality rate

Mortality rates for a specific disease may differ greatly by ethnic group, social class, sex, age, region


Incidence Rate

Number of new disease cases during a specific time period    X    1,000
Population at Risk

Prevalence Rate

Number of people with a specific disease    X    1,000
Population at Risk

See discussion on HIV/AIDS in Africa



Involuntary --- slavery, ethnic persecution, war, natural disasters
Voluntary --- jobs (skilled and unskilled workers), education, marriage, retirement

Internal i.e. movement within one country (e.g. rural to urban migration)
International i.e. movement from one country to another (e.g. migration of doctors and nurses from poorer countries to richer countries to work)

Impact of Migration on Health

Involuntary migration:
Unsanitary conditions in refugee camps
Shortage of food, malnutrition likely

Voluntary migration:
Poor living and working conditions for migrant workers
Stress, culture shock, loneliness etc
Social problems e.g. prostitution, substance abuse

Migrants (workers, prostitutes, truck drivers) may transmit infectious diseases such as HIV/AIDS, TB, diphtheria.
Jet travel speeds up transmission

Squatter settlements

See discussion on Illegal Migration

Reasons for severity of HIV/AIDS epidemic in Africa

Ethnicity, illegal immigrants, work and health in the USA

Ecotourism and health