POPULATION AND HEALTH
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)
AGE-SEX COMPOSITION OF A POPULATION
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
FERTILITY
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
MORTALITY (DEATHS) AND MORBIDITY (SICKNESS)
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
Measures of Morbidity (THESE TWO RATES ARE VERY IMPORTANT)
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
MIGRATION
Immigration
Emigration
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
Discrimination
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
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