Demography Prof Iain Crombie. Demography Study of populations size and density, growth, age...
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Transcript of Demography Prof Iain Crombie. Demography Study of populations size and density, growth, age...
Demography
Prof Iain Crombie
Demography • Study of populations• size and density, growth, age distribution, fertility,
mortality,, migration and vital statistics• the interaction of all these with social and economic
conditions.
Our focus
• size • growth• age distribution• fertility• vital statistics
– births– deaths– IMR– PYLL– DALY
Population size and structure has important implications for patterns of health and disease
Population size • World population estimates:
• 2008: 6.7 billion• 2013: 7 billion• 2028: 8 billion• 2054: 9 billion
• Of 78 million people added to the world every year, 95% live in less developed countries
Growth in population by region
% population in urban areas
Population size • Interplay of births, deaths and migration
• P2 = P1 + Births – Deaths + Net migration
Scotland’s population:1855- 2002
Net migration and natural changes
Projecting the future
Scotland’s Population
Scotland’s Population: a spike
A wedge
A barrel
Scotland’s Population
Trends in births and birth rate
Infant mortality rates: Scotland
Scotland’s Population: a spike
Overall deaths and death rates
Trends in death rates among younger women
Trends in death rates among older women
A wedge
A barrel
Population pyramids • a graphic presentation of the age and sex composition
of the population• types
• Spike: high birth rate, high death rate, low growth rate, in equilibrium
• Wedge: high birth rate, low death rate, high growth rate, in transition
• Barrel / beehive: low birth rate, low death rate, low growth rate, in equilibrium
Demographic transition• a theory/ model to explain shift from SPIKE to
BARREL population pyramids • transition from high birth and high death rates to low
birth and low death rates• often seen in change from rural (poor) to
industrialized (wealthy) society
Note: changes in birth rate and mortality in infancy and childhood are very important
Demographic transition1. Population has high birth rates and high death rates (particularly at young ages) 2. Death rates begin to fall (improved environmental conditions)3. Population increases rapidly 4. Birth rates begin to fall but population has increased greatly 5. Population has low birth and death rates
Reasons for mortality decline
• improved nutrition and food distribution• better environmental conditions and sanitation
(public health movements of 19th Century)• better housing, less overcrowding
reduced infectious disease
• Note medical advances most marked after 1930
Tuberculosis mortality over time
Dependency ratio
the proportion of economically inactive (due to age)
DependencyRatio* =
Under 18 plus over 65 years
population aged 18 – 64 years
* minimum age varies from 15 - 20 maximum age sometimes 60, may rise to 70
Is this a useful measure? Why?
Calculating the dependency ratio
Pakistan, which is a developing country, has 41% of its population <15, 4% over 65. 55% between the ages of 15 and 64.
Dependency ratio = = 81.8
23+1265
New Zealand, a developed country, has 23% of its population <1512% over 6565% between 15 and 64.
Dependency ratio = = 53.8
41 + 455
Predicted changes in Age structure:Scotland 2003 - 2028
Predicted changes in factors influencing the dependency ratio
Exploring key death rates
Infant mortality rates Under five mortality rates Maternal mortality ratio
Infant mortality rate
No of deaths of infants aged 0 –1 yearNo. of live births
for specific time period per 1,000
276 infant deaths * 1,00055,147 live births
in Scotland in 1999
Infant mortality rate 5.0 per 1,000
Infant mortality rates: England and Wales
0
50
100
150
200
Year
Infa
nt
mo
rtal
ity
rate
1841 1866 1891 1916 1941 19661966 1991
Infant mortality rate
UK turn of century: IMR = 140Sub-Saharan Africa today: IMR = 100Developed countries today: IMR = 5-10
measure of population’s state of health general - food, sanitation, overcrowding quality of health care – especially when rates low
international indicator
Comparing the health status of countries
Country Infant mortality rate Per capita health care expenditure (US$)
Singapore 2.31 816
France 3.3 2109
UK 4.85 1835
Cuba 5.72 185
US 5.82 4887
Mexico 18.42 370
Morocco 36.88 59
Yemen 54.7 20
Ethiopia 80.8 3
Afghanistan 151.95 8
Angola 180.21 31
2001
An alternative measure: under-five mortality
Why is under-five mortality one of the Millenium Development Goals?
Millenium Development Goals for 2015
189 Countries – September 2000 – Declartion at the UN
Child mortality target: to reduce by two-thirds, between 1990 and 2015, the under five years old mortality rate, from 93 children of every 1,000 dying to 31 of every 1,000
% of under 5 deaths by region
Factors associated with Child Mortality
Evaluation of progress 2010
On trackInsufficient progressNo progress
Maternal mortality ratio
deaths during pregnancy or within 42 days of termination associated with or aggravated by pregnancy expressed per 100,000 live births per year - ratio
What does the graph show?
Under-5 mortality rate 1970-2013
Lancet, Wang et al 2014
Fact sheet 2010
350,000 women die annually from complications during pregnancy or childbirth 99 per cent — in developing countries
maternal mortality rate is declining only slowly the vast majority of deaths are avoidable
Risk sub-Saharan Africa -1 in 30 developed regions - 1 in 5,600
More population measures
fertility rate life expectancy healthy life expectancy PYLL DALY
Fertility rates live births per 1,000 women per year
aged 15 – 44 years aged 15 – 49 years
age specific fertility rates total period fertility rate
Scotland fertility rate 1861-2001
Age specific fertility rates E&W 2004
Fertility rate per 1000
Age group
Fertility rates in Scotland
Two main findings?
Total Period Fertility Rate (TPFR) the average number of children that would be born to a
woman over her lifetime assumes that a woman
has the same fertility as the population on average lives beyond the maximum age of giving birth
UK: 1.84 TPFR > 2.1 population increasing TPFR < 2.1 population decreasing } why?
Calculating TPFR
Age Age-specific fertility rate per 1,000 women
Rate x 5 years
< 20 26.9 134.5
20-24 73.3 366.5
25-29 98.6 493
30- 34 99.4 497
35-39 48.9 244.5
40+ 10.4 52.0
1787.5
1,787.5 per 1000 women
TPFR=1.78 (per woman)
Round the world
TPFR
Hong Kong 1.02
Japan 1.21
Cuba 1.61
China 1.79
United States 2.05
Ecuador 2.51
Ghana 3.68
Sierra Leone 5.88
Niger 7.75
Total period fertility rates
Factors associated with high fertility
PovertyExtended family structurePastoral / agrarian economyReligionLow socio-economic statusIgnoranceEarly marriagePro-natalist policies
Factors associated with low fertility
AffluenceNuclear family structure Industrial economyReligionHigh socio-economic statusEducationDeferred marriageAnti-natalist policies
Expectation of life at birth: 1861-2001
Life expectancy
the number of years a baby born today can be expected to live IF it experienced the current age-specific mortality rates
an average for the whole population some people will live longer other less
apply age specific mortality rates 0-1, 1-4, 5-9, 10-14.....50-54.....105-109 in sequence to a population of 100,000 add up the total number of years lived / 100,000 the calculation is not examinable
77.577.377.1
75.473.773.472.872.571.9
62.662
59.4
Male life expectancy 1998-2000
Russian FedBelarusUkraineSloveniaChile
SCOTLANDCosta Rica
CubaEnglandIcelandSwedenJapan
UK Life expectancy 2006
At birth At age 65Male Female Male Female
England 77.2 81.5 17.2 19.9Wales 76.7 81.7 16.9 19.6Scotland 74.8 79.7 16.0 18.7Northern Ireland 76.2 81.2 16.8 19.7
What do these data show?
Life expectancy at birth, England and Wales, 1980-1982 to 2009-2011
Life expectancy at age 65, England and Wales, 1980-1982 to 2009-2011
Percentage Change in Life Expectancy, England and Wales 1980-1982 to 2009-2011
Healthy life expectancy
expected years of life in good or fairly good general health
two types life expectancy in good general health disability-free life expectancy (no long term limiting illness)
assumes current patterns of mortality and morbidity remain unchanged
calculation similar to life expectancy
UK Health expectancies
Life expectancy
Healthy life expectancy
Disability-free life expectancy
At birth Male 76.9 68.2 62.4Female 81.3 70.4 63.0
At age 65 Male 16.9 12.8 10.1Female 19.7 14.5 10.6
What do these data show?
Potential years of life lost: PYLL
a measure of the relative impact of various diseases and lethal forces on society.
highlights the loss to society from early deaths. should live to 75 die at 40 lose 35 years
JM Last
Calculating the PYLL
the number of years of life "lost" when a person dies "prematurely" i.e. before age 75 dies at 25, loses 50 years dies at 57, loses 18 years calculate average number lost
can use a different maximum age 65, 70 or 85
all causes or death or specific causes cardiovascular cancer
PYLL Index
Deaths in male due to road traffic accidents in Tayside: set maximum age at 70 years
Agea)
Remainingyears
d)Deaths a) x d)
0-4 67.5 5 337.55-9 62.5 3 187.5
10-14 57.5 4 230.0- - - -- - - -- - - -
65-69 2.5 10 25.0
Total 3380
Total pop = 192,500PYLL = 3380 / 192,500 = 17.6 per 1,000
PYLL data: US 2005
Disability-adjusted life years (DALYs)
measure of burden of disease extent to which disease reduces healthy years of life
1 DALY= 1 healthy year of life lostcalculated for specific diseases
DALYs
disability plus mortality disability
= incidence x duration x disability
mortality years lost through early death
DALY = years lost (death) plus years spent with disability
(allowing for the amount of disability)
Adjustment for DALYs
example women lives for 10 years in moderate pain,
disability weighting 0.4. Dies 5 years younger than life expectancy
DALY= 0.4x10 + 5 = 9
disputed the adjustment for the amount of disability
Leading Causes of Mortality and Burden of Disease
world,
%1. Ischaemic heart disease
12.22. Cerebrovascular disease
9.73. Lower respiratory infections
7.14. COPD
5.15. Diarrhoeal diseases
3.76. HIV/AIDS
3.57. Tuberculosis
2.58. Trachea, bronchus, lung cancers 2.39. Road traffic accidents
2.210. Prematurity, low birth weight 2.0
%1. Lower respiratory infections
6.22. Diarrhoeal diseases
4.83. Depression
4.34. Ischaemic heart disease
4.15. HIV/AIDS
3.86. Cerebrovascular disease
3.17. Prematurity, low birth weight 2.98. Birth asphyxia, birth trauma
2.79. Road traffic accidents
2.710. Neonatal infections and other
2.7
MortalityMortality DALYs
Leading Causes of Mortality and Burden of Disease World, 2004
WHO. Global Burden of Disease 2004 Update
What you should know Population pyramids Dependency ratio Infant mortality rate Fertility rates Life expectancies PYLL DALY
what they are – definition what they mean – interpretation what influences them
Mid Pt Years lostNo. of deaths from suicide Years lost
0-14 yrs 7.5 67.5 3
15-24 yrs 20 55 90
25-34 yrs 167
35-44 yrs 138
45-54 yrs 93
55-64 yrs 70
65-74 yrs 47
Mid Pt Years lostNo. of deaths from suicide Years lost
0-14 yrs 7.5 67.5 3 202.5
15-24 yrs 20 55 90 4950
25-34 yrs 30 45 167 7515
35-44 yrs 40 35 138 4830
45-54 yrs 50 25 93 2325
55-64 yrs 60 15 70 1050
65-74 yrs 70 5 47 235
Total years lost = 21,067.5
Total pop = 5,120,000
PYLL = 21,067.5 ÷ 5,120,000 = 4.12 per 1000
Age Age-specific fertility rates
Rate x 5
< 20 43.0 215
20-25 97.2 486
25-29 112.9 564.5
30-34 118.3 591.5
35-39 55.6 278
40+ 14.4 72
Cumulative birth rate 2,207 per 1000 women
TPFR = 2.2 (per woman)