1. Global Burden of Disease
Arindam Basu,
4th March, 2013

2. Concepts and models

3. Who Enjoys Most Health?
Full Health Disease/Injury Disability
Ann, 34, F
Bob, 60, M
Tom, 40, M
Jan, 80, F
2012
2007
(Year of their death)

4. How Can We Bring Diseases and
Deaths into One Common Rubric?
Why Should We Need to do that?

5. Problems of Reliance on Standard
Epidemiological Data
• Aggregate Measures can become unwieldy
• Many Problems of validity
• Not good for comparisons
• Partial and fragmented health statistics
• Risk of Overestimation
• Separate measures for death and
incidence/prevalence

6. What is GBD
• GBD is a comprehensive effort to estimate
these summary measures
• GBD uses Disability Adjusted Life Years
• DALY = YLL + YLD
• Disability == Health Loss, other than death
• Seven institutions - IIHME, UQueensland,
WHO, Hopkins, Harvard, Imperial College,
Tokyo Uni

7. Why Do We Need GBD?
• Need to Understand what is the “problem”, or “big
picture”?
• What are the problems? Are they getting better or
worse?
• Combine this with effectiveness, equity, for policy
• Compare overall population health across
communities
• Compare over time
• Get a coherent overall picture of diseases that
contribute most to loss of health
• What are our best data sources?
• What data sources are high quality sources?

8. Life Expectancy, YLL, and YLD
(Life Expectancy At Birth)
Birth Death
Life Expectancy At Birth
(Years of Life Lost)
Life Expectancy At Birth
(YLD, years lived with disability)

9. Concept of YLL and YLD
(Life Expectancy At Birth = 80 years)
Birth Nothing happens, guy lives for 80 years & dies Death
Life Expectancy At Birth
Guy dies @ age 50 (YLL, Years of Life Lost = 30)
Life Expectancy At Birth
Guy becomes *50%
disabled* @ age 50 (YLD, years lived with disability = 15 years)

10. Concept of GBD and DALY

11. Why DALY
• Easy and comprehensive to conduct
• Easy to understand, straightforward
• Summary measure of population health
• Led to increased attention to mental health
• Led to increased attention to
noncommunicable diseases

12. Concept of DALY
DALY == DISABILITY/DEATH ADJUSTED LIFE YEARS
DALY = YLD + YLL
YEARS OF LIFE LOST DUE TO
YEARS Lived with DISABILITY DEATHS
THIS CONCEPT IS APPLICABLE TO THE WHOLE POPULATION ACROSS AGE- AND SEX-
AND FOR DIFFERENT DISEASE ENTITIES AND RISK FACTORS, AND DEATH

13. “Time" is the most appropriate
metric
• Years Lived
• Years lost due to death
• Years lived in health states
• Years lost due to health states

14. loss function
• Years lost as a function of the age at which
death occured
• YLL(c,a,s) = N(c,a,s) * L(a,s)
• N(c,a,s) = Number of deaths due to cause
“c”, given age “a” and gender “s”
• Loss function is based on life expectancy at
age 80 (male), 82.5 (female)

15. Value choices (For Class Debate)
• How long should people in good health
expected to “live”?
• National Level?
• Globally?
• Should there be time discounting?
• 3% time discounting (in the last iteration,
removed in 2010 version)

16. Are lost years of healthy life valued
more at some ages? (Class Debate)
• Real problems
• Social Values and choices based on them
• Age Weights
• More weights for deaths at < 39 years
compared to olderyears
• Most Contentious
• These are removed in this iteration as well

17. YLL = Years of Life Lost
This is the simplest form of defining years of life lost from a population perspective.
1. No of deaths at each age group (Age-specific death rate * Population)
2. Standard Life Expectancy at that age of death

18. Comparison between Disease Ranking,
using death rates versus YLL

19. Murray’s Value Choices: Questions
• How Long Should People in Good Health
Expect to Live?
– Will this be locally determined?
– Will this be same for all people in the world?
– ??
• How Should We Compare
– Years of Life lost through death
– Years lived with Disability? Poor Health?

20. YLL with Discount Rate Added

21. Years Lived with Disability
Disability Weight (DW) ranges between 0 and 1
0 == No Disability Whatsoever, full health
1 == Completely Disabled, in other words, Dead (Death)
•This is the simplest situation
•Disability Weights are Societal Preferences

22. Disability Weights and Questions
• Disability Weights are Social Preferences, not
values
• Is a Year of Healthy Life NOW worth more to
Society than Healthy Life gained in FUTURE?
• Are Lost years of healthy life values MORE at
some ages THAN at other ages? (What
happens or should happen with old age and
very young age?)

23. Example Weights

24. Measures of Health Gaps
• Lost years of full health
• DALY is a health gap measure
• permits categorical attribution

25. Concept of YLD (Years Lived with
Disability)
• yld(c,a,s) = I(c,a,s) * dw(c,a,s) * l(c,a,s)
• I(c,a,s) == age-sex stratified incidence
• dw(c,a,s) == disability weight for c, for age a
and gender s
• l(c,a,s) == duration in years of the disease c
until remission or death

26. Achievement of GBD and DALY
Approach
• Quantified Burden of Disease
• Developed Estimates of incidence,
prevalence, duration, case fatality
• Charted over 500 sequelae
• Analyzed physiological, social, behavioural
risk factors
• Stratified by Age/Sex/Region

27. How is GBD 2010 Different Now
from Earlier?
• DALYs in GBD 2010 has removed
discounting and age weighting
• DALYs in GBD 2010 is simpler but more
comprehensive

28. Calculation of DALYs in GBD 2010
• Has not included age weighting, no
discounting
• Reference Standard population is based on
lowest age-specific death rates across
countries
• Disability Weights based on general public
perception NOT experts

29. Philosophy of GBD 2010
• Do NOT allow advocates for the importance
of specific diseases to choose the disability
weights associated with specific disorders
• All sources of data have information
• Internally consistent measures possible

30. Goal of GBD 2010
• Synthesise available data on the epidemiology
of all major diseases+injuries
• Comprehensive and comparable assessment
of the magnitude of 291 dieases+injuries

31. Methods and Study Design
• The world was divided into 21
epidemiological regions
• 20 age groups
• Total of 291 diseases (diseases and injuries
== diseases)
• Diseases are organized in four levels of
disaggregation

32. Methods (causes of death)
• YLL computed for 235 of 291 causes
• YLL = N * L (Number of deaths * gap years
of life expectancy)
• Two disorders only cause YLLs (SIDS, and
Ruptured Aneurysm*)

33. Sources of Cause of Death
• Vital Registration
• Verbal Autopsy
• Surveillance
• Other sources (epidemiological studies,
surveys, etc)

34. How Death Rates for Various
Diseases Were Calculated
• Used Cause of Death Ensemble Model (Consem
model)
• Otherwise modeled deaths based on causal
diagrams
• Obtained data from vital registration systems
and other sources
• Caution: All cause mortality estimates must be
consistent with the sum of cause specific
mortality
• (Discussion Item: why is that important??)

35. Methods (YLD)
• YLD == Years Lived with Disability
• Estimated for 1160 sequelae
• YLD = Prevalence * Disability Weights
(Prevalence = Incidence * Duration in steady
state)

36. Methods (Prevalence Estimation)
• Systematic Analysis of Published and
available unpublished data sources
• Prevalence, Incidence, Remission, excess
mortality
• Used DisMoDMR software to model the
prevalence

37. Methods (Disability Weights)
• Measured for 220 unique health states
• 1160 disease sequelae
• Why are Number of Health States Lower
than Number of Sequelae?
• Disability Weights were based on population
based surveys (N = 3100) worldwide
• Disability Weights studies involved asking the
respondent to compare two alternative health
states and rate them

38. How to Set up Rank Lists (the
purpose of GBD)
• Choose the level in the cause hierarchy
• They chose Second Level 21 causes
• Another cause list of 176 causes
• Causes were clustered under broader
categories
• Regions were set up on the order of their
mean age of death (Why??)

39. So, what did they find?
• 2010: 2.49 Billion DALYs (360 dalys per 1000)
• 31.2% from YLDs, 68.8% from YLL
• YLD make little contribution in neonatal age
group
• Global DALYs decreased slightly from 2·503
billion in 1990 to 2·490 billion in 2010
• broad composition of the burden of disease has
shifted from communicable, maternal, neonatal
and nutritional dis- orders to NCDs and injuries.

40. Top Ten Diseases, 2000 GBD Estimates

41. Top Ten Leading Causes of Disability,
GBD 2001

42. Groups of Disease, GBD 2010

43. Country Wise Comparison of
Distribution of Disease Impacts, GBD
2001

44. Comparison between profiles 1990-
2010

45. GBD Comparison: 1990-2010

46. How Non-fatal Diseases are Gaining

47. Age Distribution of DALYs, GBD 2010

48. Implications
• Health system investment decisions
• Capital investment of health system will need to
take into account the fact about shift from
communicable to non-communicable disease
load
• Content of Education?
• Time to plan for better musculoskeletal disease
management (common, weighted higher, better
assessed, new information uncovered)

49. Resources?
http://www.healthmetricsandevaluation.org/tools/data-visualizations