Global Burden of Disease: An Introduction

Kirk R. SmithProfessor of Global Environmental Health

Designing Strategies for Neglected Disease Research Jan 20, 2009

Law 284.26, Public Policy 290, 190

What is health?• “Health is a state of complete physical,

mental and social well-being and not merely the absence of disease or infirmity.”– First of nine principles on first page of World

Health Organization Constitution adopted in NYC in July 1946 by 61 nations

– “spiritual well-being” added in 1999 by World Health Assembly, which at that time had 191 member states

• http://www.ldb.org/iphw/whoconst.htm

How would this be operationalized for the following common queries?

• What is the total impact of disease and injury in the population? -- the overall target for public health interventions?– Which diseases are most important for which groups?– Are things getting better or worse?

• How do we compare the impacts of different risk factors and potential interventions that affect different populations? – For example, what is the burden of disease from environmental

factors?– How does the impact of tobacco smoking compare to that from

air pollution?

Environmental Health Effects• Example of results from outdoor air pollution studies

– Asthma attacks– Missing workdays– Missing school days– Days with cough– Emergency room visits– Hospital admissions– Physician visits– Medication use– Daily death rate– Lung function– Self-reported health status– Etc.

• How can these be compared across time, cities, countries, age groups, sectors (e.g., transport versus power plants), etc.?

• Let alone compared with the health impacts from completely different risk factors, such as water pollution, lead exposure, high cholesterol, unsafe sex, etc.?

Ultimate Measure of Ill-health?

• Death is most common– Easy to determine– Commonly tabulated

• Severe problems as a measure– Everyone dies– Health never achieved– Age is clearly important

• Deaths + Illness = ?

Combined Measure• What else to use?

– Money? Are you kidding?– Is used in legal and other realms, but not

appropriate for public health• Most fundamental deprivation is loss of time:

– Same potential life length shared by all humans – The degree to which a person does not achieve this life

length is a measure of ill-health– Can be used for disabilities, as well, but need to weight

relative severity of disabilities as well as tabulate their duration

Health Adjusted Life YearsHALY

• Basically the number of fully healthy life years lost to a particular disease or risk factor.

• Considers the age at which the disease or death occurs and the duration and severity of any disability created.

Global Burden of Disease Database

• Developed at Harvard University originally for the World Bank

• Extended greatly in the mid-1990s and now adopted by the World Health Organization– Updated database published on web each year and

summarized in World Health Report• Dozens of countries now have NBDs• Even states (provinces) and cities have them,

including SF and LA

Need for a C4 Database in Health(Which we have had in many other fields for long periods)

• Combined mortality and morbidity• Complete

– Much of the world unrepresented in past databases– Many important disabilities unaccounted

• Consistent definitions of disease states• Coherent

– Deaths by disease need to add to total• By age and sex• Match with demographic stats

– No natural discipline, i.e. no import stats from the afterlife tabulating how many died of what

Just having coherence in mortality is valuableGlobal Deaths in 2002

0

5

10

15

20

25

0-4 5-14 15-29 30-44 45-59 60-69 70+

Age Groups

MillionDeaths

LDCs

MDCs

Total PopulationLDCs – 4.78 billionMDCs – 1.45 billion

Total Global Deaths in 2002: 57 million

Disability Adjusted Life YearThe DALY, a kind of HALY

• Principle #1: The only differences in the rating of a death or disability should be due to age and sex, not to income, culture, location, social class.

• Principle #2: Everyone in the world has right to best life expectancy in world

• DALY = YLL + YLD– Years of Lost Life (due to mortality)

– Years Lost to Disability (due to injury & illness)

Years of Lost Life: ExamplesAge at Death Female Male0 82.5 80.01 81.8 79.55 78.0 75.415 68.0 65.425 58.2 55.535 48.4 45.650 34.0 31.080 8.9 7.5100 2.0 1.5

100

What is Meant by “Disability?”• Impairment: Symptoms at organ level, e.g.,

broken leg• Disability: Objective alteration of behavior or

performance at the individual level, e.g., cannot walk

• “Handicap”: Changed interaction with others at the social/environmental level, e.g., cannot work

• http://www.disabilityhelper.com/Disability-Impairment-Handicap.htm

Schema for Assessing Non-fatalHealth Outcomes

Disease Impairment

Polio Paralyzed legs

Brain Mild mentalinjury retardation

Disability “Handicap”

Inability Unemployedto walk

Difficulty Sociallearning isolation

Whom do you ask to determine disability weights?

• Patient• Family• Caregiver• Health professional• Public health experts• Public at large• Insurance companies and lawyers (court cases)

Used in GBD

Time

Accident

ReportedDisabilityWeight

1.0

When do you ask?

Classes of Disability Weights, with examples

1: 0-0.02 Vitiligo on face2: 0.02-0.12 Diarrhea, sore throat3: 0.12-0.24 Radius fracture in stiff cast4: 0.24-0.36 Below the knee amputation5: 0.36-0.5 Down syndrome, COPD6: 0.5-0.7 Unipolar depression, tetanus7: 0.7-1.00 Psychosis, quadriplegia

Top Ten Causes of Disability in 15-44 year olds (2000)

Male FemaleUnipolar depression 13.9 18.6Alcohol disorders 10.1Schizophrenia 5 4.8Bipolar depression 5 4.4Fe-Deficiency anaemia 4.2 5.4Hearing loss 4.1 3.6Road traffic 3.8HIV/AIDS 3.2 2.5Drug use 3COPD 2.6Obstructed labor 4Chlamydia 3.3Abortion 3.1Panic disorder 2.8

Percent of Total YLDs

Sample DALY CalculationsDiseases A and B

• A. 100,000 children are stricken for 1 week with a disability weighting of 0.3; 2% die at 1 year old.

• B. 100,000 adults are stricken for 2 years with a disability weighting of 0.6; 20% die at 80 years old.

• A: YLL (= 2000 x 80) + YLD (=100k x (7/365) x 0.3) = 160,000 + 575 = 160,600

• B: YLL (= 20,000 x 8) + YLD (=100k x 2 x 0.6) = 160,000 + 120,000 = 280,000

Global Burden of Disease DatabaseWorld Health Organization

Being completely updated2007-2009

Occam's Razor• “One should not increase, beyond what is necessary,

the number of entities required to explain anything”

• Occam's razor is a logical principle attributed to the 14th Century philosopher William of Occam (or Ockham). The principle states that one should not make more assumptions than the minimum needed. This principle is often called the

Principle of Parsimony

The DALY Passes Occam’s razor criterion, because it reveals something different from deaths

Deaths DALYs 1 – Cancer 12.4% 5.3% (4) 2 - Heart 12.3% 3.8% (7) 3 - Stroke 9.2% 3.1% (9) 4 - ARI 7.1% 6.6% (1) 5 - HIV 5.3% 6.1% (3) 7 – Perinatal 8 - Diarrhea ? - Depression

4.4% 3.8% 0.03%

6.2% (2) 4.2% (6) 5.3 % (5)

Examples of Using a C4 database:World DALYS Lost (2000)

Pop million

Deaths million

Deaths per 1000

DALYs million

DALYs Per Death

LDCs 4693 43.3 9.2 1256 29.0

MDCs 1352 12.4 9.2 216 17.4

World 6045 55.7 9.2 1472 26.4

Impact of Development on Women and Children

W & C share of Pop

W & C share of DALYs

South Asia 66% 71%

Western Europe 60% 49%

World 65% 67%

Children under 15 years in 2000

2000

World - Deaths

0 5 10 15

Road Traff ic

Child Cluster

TB

Diarrhea

Perinatal

COPD

HIV

ARI

Stroke

Cancer

Heart (Ischaemic)

Percent of Total

World Deaths in 2000

Child Cluster Diseases: the World’s Largest Scandal

• 1.4 million children• Rates in LDCs are

thousands of times those in MDCs (Africa = 4700x that of W. Europe)

• Vaccine coverage in Africa went from 60% in 1990 to 46% in 1999

• Has stayed at 70% in South Asia for many years

Measles 777000Tetanus 309000Pertussis 296000Diphtheria 3400Poliomyelitis 675

Total Global Deaths in <5y

Relative Risks between Poor Africa and USA

• Chance of woman dying in childbirth: 400 times greater

• Child dying of diarrhea: 400 times• Of pneumonia: 500 times• Of measles: 4000 times

• Similar in South Asia (India, Bangladesh, etc)

2000

World - DALYs

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0

Congenital

COPD

Maternal

TB

Malaria

Road Traffic

Stroke

Malnutrition

Child Cluster

Heart (Ischaemic)

Diarrhea

Cancer

Depression

HIV

Perinatal

ARI

Percent of Total

World DALYs in 2000

The major disease targets for publichealth interventions in the worldtoday

Almost allWomen &Children

2000

North America - Deaths

0.0 5.0 10.0 15.0 20.0 25.0

Dementia

Diabetes

ARI

COPD

Stroke

Heart (Ischaemic)

Cancer

Percent of Total

20002000

North America - Deaths

2000 North America - DALYs

0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0

Osteoarthritis

Hearing loss

COPD

Diabetes

Dementia

Road Traffic

Stroke

Alcohol

Heart (Ischaemic)

Depression

Cancer

Percent of Total

20002000

The major disease targets for public health interventionsin the USA

222

178

118

107

92

90

86

86

75

67

67

59

59

52

47

39

0 50 100 150 200 250

Very poor Africa

Poor Africa

Poor Eastern Med

Poor South Asia

All Men

Former USSR

Poor Latin America

All Women

Middle income South Asia

Middle income Latin America

Eastern Europe

China +

Middle income Eastern Med

North America

Western Europe

Japan, Australia +

DALD/capita

Disability AdjustedLost Days = DALY x 365

2000

Global

0

100

200

300

400

500

600

Very poor Africa 548 57 174 264 191 193 218 212

Poor South Asia 307 44 75 80 114 157 169 159

Poor Latin America 198 34 74 75 93 120 140 160

Middle Income East Asia 146 24 44 43 67 107 139 158

North America 35 14 51 43 58 87 110 111

Western Europe 29 11 39 33 48 79 98 110

Japan/Australia 32 13 31 27 41 59 75 91

0-4 5-14 15-29 30-44 45-59 60-69 70-79 80+

DALDsPer Capitaby AgeGroup

SelectedWorld Regions

2000

Annual loss per person

Time

The Classic Epidemiological Transition

Non-CommunicableDiseases

Infectious Diseases

Cancer

CVD

Disease Categories• I - Traditional, Communicable

– Infectious, maternal, perinatal, nutritional• II - Modern, Non-communicable

– Cancer, heart, neuro-psychiatric, chronic lung, diabetes, congenital

• III - Injuries, Non-Transitional– Unintentional

• Motor vehicle, poisoning, falls, fire, drowning

– Intentional• Suicide, violence, war

Classic Epi Transition

• I. Infectious diseases decline during development

• II. Chronic disease rise during development• III. Injuries show no pattern during

development and are thus “non-transitional”

Empirical Test of the Epi Tranistion

• Does it hold up to examination using the first C4 database?

• Classic epidemiologic transition only deals with mortality, thus here termed the “Mortality Transition”

• “Epidemiologic Transition” here applied to same evaluation using DALYs

Epidemiological Transition - Age Adjusted

98

9

32

46

168

112

87

120

111

129

29

12

25

28

37

0 50 100 150 200 250 300 350 400

World

High

Upper Middle

Lower Middle

Low

Inco

me

Gro

up

DALYs per thousand

I - "Infectious" II - "Chronic" III - Injuries

Epi Transition: Updated• In terms of actual age-adjusted impact on

populations, all classes of disease decline during development– I. Declines dramatically at every level– II. Declines slowly, but with little decline seen across

middle income regions– III. Declines in a similar way to II and thus is not “non-

transitional”• Better to be rich for all major types of ill-health,

although there are exceptions for individual diseases

Comparison of GBD Estimates for 2005 with GBD for 1990

• Population: 5.3/6.4 billion (+21%)• Deaths: 50/64 million (+28%) • DALYs: +7%• DALYS/capita: -11%• I = 44/38.5%; • II = 41/48.9%; • III = 15/12.5%

WHO Databases

Changes in Important Diseases: 1990-2005What is happening with each?

• Diarrhea: 7.3/3.9% (-42% in absolute terms)• ARI: 8.5/5.9% (-25%)• Malaria: 2.3/2.3% (-6%)• Lung Cancer: 0.65/0.8% (+32%)• TB: 2.8/2.1% (-18%)• HIV: 0.8/5.6% (7.4 times as much)• Depression: 4.7/5.8 (+29%)

WHO Databases

Can we reach public health?

• Is there a absolute value of health (lost DALYs) beyond which society does not have an obligation to exceed?

• Is there a cost per unit improvement in health ($ per DALY) above which society does not benefit from further expenditure?

World Health Reports – 2002, 2001

4.9 million deaths/y

Global Burden of Disease from Top 10 Risk Factorsplus selected other risk factors

0% 2% 4% 6% 8% 10%

Climate change

Urban outdoor air pollution

Lead (Pb) pollution

Physical inactivity

Road traffic accidents*

Occupational hazarads (5 kinds)

Overweight

Indoor smoke from solid fuels

Lack of Malaria control*

Cholesterol

Child cluster vaccination*

Unsafe water/sanitation

Alcohol

Tobacco

Blood pressure

Unsafe sex

Underweight

Percent of All DALYs in 2000

Environmental Risk Factors

Entry into GBD databases• Best single modern book covering the GBD and CRA ideas, methods,

and results, but without full detail and sophistication/complexity:  Global Burden of Disease and Risk Factors, (Lopez, Mathers, Ezzati, Jamison, Murray) Oxford University and World Bank Presses, 2006.  475 pp.  Fully downloadable at http://www.dcp2.org/pubs/GBD which also has links to data used in the book.

• Best single page to find GBD data divided by world regions defined in several ways (WHO regions, World Bank regions, income groups etc.) for 2004. http://www.who.int/healthinfo/global_burden_disease/2004_report_update/en/index.html

• For projections to 2030 and links to dozens of other publications, see http://www.who.int/healthinfo/global_burden_disease/en/index.html

• The full set of background materials and pubs of the previous (2004) Comparative Risk Assessment (CRA) covering 26 major risk factors, environmental and other: http://www.who.int/healthinfo/global_burden_disease/cra/en/index.html

• Full databases for the previous CRA study: http://www.who.int/healthinfo/global_burden_disease/risk_factors/en/index.html

• Description of the GBD/CRA 2005 Revisions now underway: http://www.who.int/healthinfo/global_burden_disease/GBD_2005_study/en/index.html

Thank you.

Kirk R. Smithkrksmith@berkeley.eduhttp://ehs.sph.berkeley.edu/krsmith/