Measuring
Global Burden of Disease
Ashwini Kalantri
Moderator:
Dr Pradeep Deshmukh
Global Burden of Disease
• Rationale (Why?)
– Assess health status over time
– Input to health decision-making and planning
processes
Global Burden of Disease – How?
•
•
•
•
Morbidity indicators
Mortality indicators
Disability indicators
Nutritional status
indicators
• Health Care delivery
indicators
• Utilization Rates
• Indicators of Social
and Mental Health
• Environmental
Indicators
• Socio-economic
Indicators
• Health Policy
Indicators
• Indicators of quality of
Life
Global Burden of Disease
• Summary measures of population
health: measures that combine
information on mortality and non-fatal
health outcomes to represent the health of
a particular population as a single number
History
• 1940s: Concept of “Years of Life Lost”.
• 1971: Sullivan’s Index
• 1983: Quality Adjusted Life Expectancy
(QALE).
• 1990: GBD study – DALYs.
• 1998: HeaLY
• DALE, HALE, QALY, DFLE followed
SMPH - Types
Health Expectancy
Health expectancies
measure years of life gained
or years of improved quality
of life.
– Disability-free life
expectancy (DFLE)
– Disability-adjusted life
expectancy (DALE)
– Healthy adjusted life
expectancy (HALE)
– Quality adjusted life
expectancy (QALE)
Health Gaps
Health gaps measure lost
years of full health in
comparison with some
‘ideal’ health status or
accepted standard.
– Potential Years of Life Lost
(PYLL)
– Quality Adjusted Life Years
(QALY),
– Disability Adjusted Life
Years (DALY)
Survival Curve
100
C
90
80
B
% Surviving
70
Time lived in
suboptimal health
60
Time lost due to
mortality
50
40
A
30
Time lived in optimal
health
20
10
0
0
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 100
Age
Life Expectancy
• Total life expectancy at birth is given by
the area under the upper curve
• Total life expectancy at birth = A + B
100
C
80
• A = time lived in optimal health
• B = time lived in suboptimal health
60
40
20
0
B
A
Health Expectancy
• Health expectancies are population indicators
that estimate the average time that a person
could expect to live in a defined state of health
• Health Expectancy = A + f (B)
100
• A = time lived in optimal health
• B = time lived in suboptimal
health
• f (B) = function that assigns
weights to years lived in
suboptimal health (optimal health
has a weight of 1)
C
80
60
40
20
0
B
A
Health Gaps
• Health gaps measure the difference
between actual population health and
some specified standard or goal
• Health Gap = C + f (B)
100
• B = time lived in suboptimal
health
• C = time lost due to mortality
• f (B) = function that assigns
weights to health states lived
during time B, but where a weight
of 1 equals to time lived in a
health state equivalent to death
C
80
60
40
20
0
B
A
DALE
Disability Adjusted Life Expectancy
• DALE integrates data on
– Mortality
– Long – term institutionalization
– Activity limitations
• Measures Quality and Quantity of life
• A set of weights is assigned to four states of
health
–
–
–
–
no activity limitations
activity limitations in leisure activities or transportation
activity limitations at work, home and/or school
institutionalization in a health care facility
HALE
Health Adjusted Life Expectancy
• Health-adjusted life expectancy is the number
of years in full health that an individual can
expect to live given the current morbidity and
mortality conditions.
• Health-adjusted life expectancy uses the
Health Utility Index (HUI) to weigh years lived
in good health higher than years lived in poor
health.
• Measure of quantity and quality of life
QALY
Quality Adjusted Life Years
• Measures both quality and quantity
• Used for cost-benefit analysis
• Number of years added due to the
intervention
DALY
Disability Adjusted Life Years
DALY is a measure of overall disease
burden, expressed as the cumulative
number of years lost due to ill-health,
disability or early death
DALY
Objectives
• Inclusion of non-fatal health outcomes in
the debate on international health policy
• To quantify the burden of disease using a
measure that could also be used for costeffectiveness analysis.
DALY
Disability Weights
• The ‘valuation’ of time lived in non-fatal health
states
• Weights are measured as a number on a scale of
0 to 1, where 0 is assigned to a state comparable
to death and 1 is assigned to a state of optimal
health
• Because the DALY measures loss of health, the
weights are inverted for DALY calculation with 0
representing a state of optimal health (no loss)
and 1 representing a state equivalent to death.
DALY
Disability Weights
• Weight for paraplegia of 0.57 - does not mean
– Half dead
– Halfway between life and death
– Society values them as a person less than anyone else.
• A year with blindness (weight 0.43) > a year with
paraplegia (weight 0.57) > a year with unremitting
unipolar major depression (weight 0.76).
• A year in good health followed by death > a year with
paraplegia followed by death.
• A person to live three years with paraplegia followed by
death > one year of good health followed by death
– (3 years x (1-0.57) = 1.3 ‘healthy’ years is greater than 1 year of
good health).
DALY
Disability Weights
Disease
Disability Weights
Tuberculosis
0.331 (0.222– 0.450)
HIV/AIDS
0.547 (0.382–0.715)
Major Depression
0.655 (0.469–0.816)
Moderate Generalized
Musculoskeletal Problems
Iodine-deficiency goitre
0.292 (0.197–0.410)
Kwashiorkor
0.055 (0.033–0.085)
Severe wasting
0.127 (0.081–0.183)
0.200 (0.134–0.283)
DALY
Discounting
• The GBD applied a 3% time discount rate
to years of life lost in the future to estimate
the net present value of years of life lost.
• With this discount rate, a year of healthy
life gained in 10 years’ time is worth 24%
less than one gained now.
DALY
Discounting – Why?
• To be consistent with measurement of
health outcomes in cost-effectiveness
analyses
• To prevent giving excessive weight to
deaths at younger ages
• Disease eradication/research paradox
DALY Calculations
DALY = Years Lived with Disability (YLD) +
Years of Life Lost (YLL)
YLD
Years Lived with Disability
• YLD = I x DW x L
• I = number of incident cases
• DW = disability weight
• L = average duration of the case until remission or
death (years)
YLL
Years of Life Lost
• YLL = N x L
• N = number of deaths
• L = standard life expectancy at age of death in yrs
DALY
Critique
• Doesn’t help determine the right
intervention
• The true “burden” of disease will depend
on the economic, family and social
circumstances
• Multi-pathology is not the same as multicausality.
DALY
Critique
• Discriminates against young and the old
• Does not assess qualitative difference in
outcomes
• No Male-Female difference in length of life
• Discounting future health outcomes
The Global Burden of Disease
Study 2010
DALYs / 1,00,000
GBD Study 2010
Cause
1990
2010
Change
Tuberculosis
1155
717
-37.9%
HIV/AIDS
342
1184
246.3%
Malaria
1304
1200
-8.0%
Common
Infectious
Diseases
10245
4107
-59.9%
Maternal Disorder
407
234
-42.6%
Mental disorders
2539
2688
5.9%
Endocrine
Disorders
1605
1777
10.7%
Musculoskeletal
Disorders
2198
2462
12%
All Causes
47205
36145
-23.4%
Global DALY Trends
India - DALY Trends
References
1.
2.
3.
4.
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References
5.
6.
7.
8.
9.
Mathers CD, Fat DM, Boerma JT, Organization WH. The Global Burden of
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World Health Organization. 1997;75(4):383.
Salomon JA, Vos T, Hogan DR, Gagnon M, Naghavi M, Mokdad A, et al.
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