Global Burden of Disease:
An Introduction
Designing Strategies for Neglected Disease Research
Jan 20, 2009
Law 284.26, Public Policy 290, 190
Kirk R. Smith
Professor of Global Environmental Health
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 Years
HALY
• 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 valuable
Global Deaths in 2002
Total Global Deaths in 2002: 57 million
25
LDCs
20
MDCs
Total Population
LDCs – 4.78 billion
MDCs – 1.45 billion
15
Million
Deaths
10
5
0
0-4
5-14
15-29
30-44
Age Groups
45-59
60-69
70+
Disability Adjusted Life Year
The 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: Examples
Age at Death
0
1
5
15
25
35
50
80
100
100
Female
82.5
81.8
78.0
68.0
58.2
48.4
34.0
8.9
2.0
Male
80.0
79.5
75.4
65.4
55.5
45.6
31.0
7.5
1.5
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/DisabilityImpairment-Handicap.htm
Schema for Assessing Non-fatal
Health Outcomes
Disease
Impairment
Disability
“Handicap”
Polio
Paralyzed
legs
Inability
to walk
Unemployed
Brain
injury
Mild mental
retardation
Difficulty
learning
Social
isolation
Whom do you ask to determine
disability weights?
•
•
•
•
•
•
•
Patient
Family
Caregiver
Used in GBD
Health professional
Public health experts
Public at large
Insurance companies and lawyers (court cases)
When do you ask?
1.0
Reported
Disability
Weight
Accident
Time
Classes of Disability Weights,
with examples
1: 0-0.02
2: 0.02-0.12
3: 0.12-0.24
4: 0.24-0.36
5: 0.36-0.5
6: 0.5-0.7
7: 0.7-1.00
Vitiligo on face
Diarrhea, sore throat
Radius fracture in stiff cast
Below the knee amputation
Down syndrome, COPD
Unipolar depression, tetanus
Psychosis, quadriplegia
Top Ten Causes of Disability
in 15-44 year olds (2000)
Percent of Total YLDs
Male
Unipolar depression
Alcohol disorders
Schizophrenia
Bipolar depression
Fe-Deficiency anaemia
Hearing loss
Road traffic
HIV/AIDS
Drug use
COPD
Obstructed labor
Chlamydia
Abortion
Panic disorder
Female
13.9
18.6
10.1
5
4.8
5
4.4
4.2
5.4
4.1
3.6
3.8
3.2
2.5
3
2.6
4
3.3
3.1
2.8
Sample DALY Calculations
Diseases 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 Database
World Health Organization
Being completely updated
2007-2009
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
12.4%
12.3%
9.2%
7.1%
5.3%
4.4%
3.8%
DALYs
5.3% (4)
3.8% (7)
3.1% (9)
6.6% (1)
6.1% (3)
6.2% (2)
4.2% (6)
? - Depression 0.03%
5.3 % (5)
1 – Cancer
2 - Heart
3 - Stroke
4 - ARI
5 - HIV
7 – Perinatal
8 - Diarrhea
Examples of Using a C4 database:
World DALYS Lost (2000)
Pop
Deaths Deaths
million million per
1000
DALYs DALYs
million 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
66%
71%
Western Europe 60%
49%
World
67%
South Asia
65%
Children under 15 years in 2000
2000
Heart (Ischaemic)
Cancer
Stroke
A RI
HIV
COPD
Perinatal
Diarrhea
TB
World Deaths in 2000
Child Cluster
Road Traf f ic
0
5
10
Pe r ce nt of Total
15
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
Total Global Deaths in <5y
Measles
T etanus
Pertussis
Diphtheria
Poliomyelitis
777000
309000
296000
3400
675
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
ARI
Perinatal
HIV
Depres s ion
The major disease targets for public
health interventions in the world
today
Cancer
Diarrhea
Heart (Is chaem ic)
Child Clus ter
Malnutrition
Stroke
Almost all
Women &
Children
Road Traffic
Malaria
TB
Maternal
World DALYs
in 2000
COPD
Congenital
0.0
1.0
2.0
3.0
4.0
Percent of Total
5.0
6.0
7.0
2000
2000
2000
Cancer
Heart (Ischaemic)
Stroke
COPD
North America - Deaths
ARI
Diabetes
Dementia
0.0
5.0
10.0
15.0
Percent of Total
20.0
25.0
2000
2000
North America - DALYs
2000
Cancer
Depres s ion
Heart (Is chaem ic)
Alcohol
Stroke
Road Traffic
The major disease targets for
public health interventions
in the USA
Dem entia
Diabetes
COPD
Hearing los s
Os teoarthritis
0.0
2.0
4.0
6.0
8.0
Percent of Total
10.0
12.0
14.0
DALD/capita
2000
0
50
100
150
200
Very poor Africa
222
Poor Africa
178
Poor Eastern Med
118
107
Poor South Asia
All Men
92
Former USSR
90
Poor Latin America
86
All Women
86
Middle income South Asia
67
Eastern Europe
67
China +
59
Middle income Eastern Med
59
North America
Japan, Australia +
Global
75
Middle income Latin America
Western Europe
250
52
47
39
Disability Adjusted
Lost Days = DALY x 365
600
DALDs
Per Capita
by Age
Group
2000
500
Annual loss per person
400
300
Selected
World
Regions
200
100
0
0-4
5-14
15-29
30-44
45-59
60-69
70-79
80+
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
The Classic Epidemiological Transition
Infectious Diseases
NonCommunicable
Diseases
Time
CVD
Cancer
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
Income Group
Low
168
Lower Middle
46
Upper Middle
111
32
High 9
World
120
87
50
37
28
25
12
98
0
129
112
100
150
29
200
250
300
DALYs per thousand
I - "Infectious"
II - "Chronic"
III - Injuries
350
400
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 “nontransitional”
• 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: 1990-2005
What 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?
Global Burden of Disease from Top 10 Risk Factors
plus se le cte d othe r risk factors
Underweight
Unsafe sex
Blood pressure
4.9 million deaths/y
Tobacco
Alcohol
Unsafe water/sanitation
Child cluster vaccination*
Cholesterol
Lack of Malaria control*
Indoor smoke from solid fuels
Environmental Risk Factors
Overweight
Occupational hazarads (5 kinds)
Road traffic accidents*
Physical inactivity
Lead (Pb) pollution
Urban outdoor air pollution
Climate change
World Health
Reports – 2002,
2001
0%
2%
4%
6%
Percent of All DALYs in 2000
8%
10%
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_updat
e/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/inde
x.html
• Description of the GBD/CRA 2005 Revisions now underway:
http://www.who.int/healthinfo/global_burden_disease/GBD_2005_study/
en/index.html
Kirk R. Smith
krksmith@berkeley.edu
http://ehs.sph.berkeley.edu/krsmith/
Thank you.