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)