This document discusses using Disability Adjusted Life Years (DALYs) to measure the traffic-related burden of disease in California. It outlines calculating DALYs from mortality and morbidity data to quantify healthy years of life lost. Preliminary results show traffic DALYs are mostly from years of life lost, with more challenging to calculate years lost to disability. Future directions include estimating potential burden reductions from interventions like increased seatbelt or decreased alcohol-related crashes.
1. Disability Adjusted Life Years
(DALYs) and the Traffic-Related
Burden of Disease in California
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2. Quick Outline
• Background
– Summary measures of health
– Disability Adjusted Life Years (DALYs)
– DALYs & the Global Burden of Disease study
– Relevance for the Traffic Safety Center
• Methodology
• Results
• Conclusions
• Future Directions
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3. Measures of Population Health:
Mortality and Morbidity Measures
# deaths, death rate, # injured, # head injuries,
# severe injuries, rate of injuries, # hospitalizations
Summary Measures
Aggregate mortality and morbidity into a
single measure
# years healthy life lost (DALYs, QALYs)
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4. Summary Measures of Population
Health: Why use them?
• Compare the health of one population with another
• Analyze the benefits of health interventions for use
in cost-effectiveness analysis
• Identify and quantify overall health inequalities
within populations
• Informing debates on health policy
• Monitor changes in the health of a given population
• Attribute burden from risk factors
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[WHO – Summary Measures of
JAVED Population Health, 2002]
5. Disability Adjusted Life Years
(DALYs)
• Measures healthy time lost from specific
diseases and injuries in a population
• Comparable and additive across diseases
Ex: Broken scapula = .5 DALYs lost
Protein deficiency = 2 DALYs lost
• Based on relatively accessible incidence
data (ICD codes)
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6. DALY Calculation
(the easiest way)
Years lost to
Years of lost life disability
+
(YLLs) (YLDs)
Inputs
Inputs
• Duration of disease/injury
• Life expectancy at age of
death • Disability weight of
disease/injury
• Age at death
• % long-term cases
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7. DALY Calculation: an example
A Two-Car Collision
1 family dies 2 people injured
– 10 year old girl – 45 y/o woman – SCI
– 8 year old boy
– 55 y/o man – fractured rib
– 38 year old mother
– 42 year old father
YLLs from deaths YLDs from injuries
– 70 year life expectancy - Duration (36 year LE) *
– 73 year life expectancy Disability Wt (.725) = 26 YLDs
– 46 year life expectancy - Duration (.115 years) * Disability
– 33 year life expectancy Wt (.199) = 0.02 YLDs
222 YLLs +
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26.02 YLDs
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= 248.02 YLDs
8. DALY Calculations: Adjustments
• Designed to allow tailoring to local social values
and specific applications for the DALYs
• Age-weighting – weights the life of a 21 year-old
(for instance) more heavily than other ages
according to societal preferences.
• Discounting – commonly used in economic
analyses, recommended for DALYs if using the
outcome measure in such analyses
• Caused much contention
• DALYs can be calculated without such
adjustments
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9. DALYs and the Global Burden of
Disease
• WHO/World Bank Global • Quick results
Burden of Disease study – Ranked 9th in cause of
outlined methodology for total DALYs in the
DALYs world in 1990
• First attempt at a – Still ranked 9th in 2000
comprehensive picture of estimates
global health
– Predicted to be ranked
• Ranked diseases according 3rd in 2020
to the number of DALYs
• Projected rankings to 2020
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10. DALYs and the Traffic-Related
Burden of Disease in California
• DALYs as a measure of traffic-related outcomes
in California
– Different than that captured by mortality or injury
alone?
• Characterize the traffic-related burden of disease
in more detail for age, gender, and ethnicity
– By occupant, pedestrian, bicyclist, etc.
• Construct a database of traffic-related DALYs for
California for use in comparisons to global,
regional, state, and city trends.
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11. Methods: Case Definitions
• GBD case definition for injury:
“One that leads immediately to death or that is non-fatal
but severe enough to warrant hospital treatment.”
• “Road Traffic Accidents” category based on the
E-codes on hospital discharge
– CDC and the GBD recommendations do not entirely
coincide
• Each injury type has a specified disability weight,
duration, % long-term cases in the GBD
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12. Methods: DALY Calculation
Data Sources
Mortality Morbidity
CA Vital Statistics OSHPD hospital
discharge data
EPIC database
EPIC database
+ Age- and sex- specific + Age- & sex-specific
deaths listed by injuries by ethnicity and
ethnicity and county county
+ Injury by E-code and
+/- ICD-10 coding for nature of injury codes
1999 and later +/- ICD-9 coding
-- Need individual level data
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13. Methods: DALY calculations
YLLs and YLDs
• Ethnicity, gender, age by External injury category
(Motor vehicle Occupant, Pedestrian,
Motorcyclist, or Bicyclist)
• Using highest world life expectancy and 3%
discount rate
• YLL calculation
• YLDs – calculated for each type of injury and
body part injured by age, gender, and ethnicity
Ex: Amputation of upper limb for 50-55 y/o Asian
males = x YLDs
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14. Methods: DALY calculations
Comparison Measures
• Sum YLLs and YLDs for population = DALYs
• Calculate the # of deaths and the # of injuries for
same categories from same data
• Test rank-order for DALYs, deaths, injuries,
others?
• Compare rates to global, regional, national, city
(San Francisco, Los Angeles) DALY rates.
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15. Results?
• Not much yet.
• Gender and age DALY calculations by
injury category is complete (as of yesterday)
• YLLs by ethnicity are complete while YLDs
are still being calculated
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16. Preliminary Results: Gender
• Consistency of the distribution of total traffic-
related burden between genders ~70%
California DALYs – 71% male
Regional DALYs – 70% male
World DALYs – 70% male
California deaths – 69% male
California injuries – 62% male
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17. Preliminary Results: Ethnicity
YLLs
Death Death
GBD YLL CDC YLL Rate per GBD CDC YLL Rate per
Females rates rates 100,000 Males YLL rates rates 100,000
White 144 119 6 White 328 274 15
Native American81
2 182 6 Native American
302 201 13
Hispanic 168 146 5 Hispanic 482 392 14
Black 143 123 8 Black 387 349 8
Asian 117 95 5 Asian 231 212 9
Death
GBD CDC YLL Rate per
Totals YLL rates rates 100,000
White 472 393 10
Native American 583 383 10
Hispanic 650 537 10
Black 531 473 8
Asian 348 307 7
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18. Conclusions thus far…
• The epi data necessary for YLD calculation
is limited.
– Primary diagnosis may not be the most severe
injury underestimation
• Traffic-related DALYs are largely
composed of the YLL (deaths)
• Future analyses will be more challenging
with HIPPA system in place
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19. Future directions…
• By how much can the burden be reduced?
How low can we feasibly get it?
• How much of the burden is attributable to
lack of restraint-use? How much could we
reduce the burden if we increase seatbelt
use by 5%? Would we get more DALYs if
we decrease alcohol-related burden by 5%?
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