introduction to daly and burden of disease

Burden of Disease: Introduction

Arindam BasuSchool of Health Sciences,University of Canterbury,

arindam.basu@canterbury.ac.nzFebruary 24, 2014

Part I: DALY AS A SINGLE GAP BASED MEASURE OF POPULATION HEALTH

Health

BIRTH DEATH

STATE of WELL-BEING

Health

BIRTH DEATH

Physical, Mental, Social WELL-BEING

Concept of Physical, Mental, Social

PHYSICAL

MENTAL

SOCIAL

0

1

1

10 = DEATH1 = FULL LIFE

Metaphor of Life

(1,1,1)

Health

BIRTH DEATH

Complete Physical, Mental, Social WELL-BEING

“And so from hour to hour, we ripe and ripe, and from hour to hour, we rot and rot; and

thereby hangs a tale” -Shakespeare

Health As a “STATE”

WATER AS A METAPHOR OF HEALTH and CHANGE of STATE

Image source: Wikimedia commons

Health

BIRTH DEATH

State of Complete Physical, Mental, Social WELL-BEING

What Is Absence of Health? Disease? Infirmity?

What is Absence of Disease?Health?

Health

BIRTH DEATH

“State of Complete Physical, Mental, Social WELL-BEING, not merely absence of disease or infirmty”

Preamble to the Constitution of the World Health Organization as adopted by the International Health Conference, New York, 19-22 June, 1946; signed on 22 July 1946 by the representatives of 61 States (Official Records of the World Health Organization, no. 2, p. 100) and entered into force on 7 April 1948.The Definition has not been amended since 1948.(http://who.int/about/definition/en/print.html)

“Health is Wealth” (Ancient Saying)

Provocation: “Is Health Resource? Or is Health Merely a “State of Existence”? Or Both? How do we reconcile?

Context of Measuring Health

PATIENTS

PAYERSPROVIDERS

MANAGERS

Different Perspectives of Measuring Health

PATIENTS

PAYERSPROVIDERS

MANAGERS

“A Case of Fever That Requires Admission in a Ward”

What is my Quality of Life?

What is the Temperature? “How Much Did it Cost?

“How Long Did the Patient Stay? (LoS)”

Constraints and Limitations of a Summary Measure of Health

The Measure Must Be

Consistent

The Measure Must Be Comparable and

Make Sense

“ONE MEASURE TO RULE THEM ALL”

The Principle

“May You Live a Long Life in Good Health”!

Health Gap

The Ideal: Individuals Live Standard Life Expectancy At Full Length

Health Gap: State of Population Health Compared to a Normative Goal

YEARS of LIFE LOST (YLL)

Natural Death at Age 86 years

He Dies at the Age of 50 Years Due to Road Traffic Injury

This person has therefore lost 86-50 = 36 YEARS of HEALTHY LIFE

Concept: YLL for Populations

Number of Deaths in the Population for An Age Group

Multiplied By

Life Expectancy At Birth for that Age (~ 86 – Age in Years)

YEARS Lived with Disability (YLD)

Natural Death at Age 86 years

He suffers RTI at the Age of 50 Years and LIVES with 50% Disability

This person has therefore lost (86-50) * 0.5 = 18 YEARS of HEALTHY LIFE

YLD for Populations

Age-Specific Prevalence of the Disease or Sequela

Multiplied By

Age-Specific Disability Weight

DALY = YLL + YLD

… AND ONE FORMULA To RULE THEM ALL …

PART II: ESTIMATE GLOBAL BURDEN OF DISEASE USING DALY

Global Burden of Disease Approach• Initiated by World Bank (1990s)• Now Seven Organizations:• IHME• Imperial College• University of Queensland• Johns Hopkins• University of Tokyo• WHO• Data from 187 countries, 291

conditions, 1160 sequela, 220 disease states

• Synthesis of Epidemiological Data

Chris Murray (L) and Alan Lopez (right) considered to be the “grand fathers” of the Global Burden of Disease Approach

World

• Data from– 187 Countries– 21 Regions

• Basis:– Geographical

Contiguity– Epidemiological

Homogeneity

Diseases

• 291 Diseases into 5 Levels of Hierarchy

• (4 Levels + 1 Health State)

• 1160 Sequelae• Common Sequelae are

termed as “Health States” – 220 health states

• 69 Risk Factors

New Normative Standard Life Table Was Used for males and females to compute YLL at each age by identifying lowest observed death rates for any age group in countries with > 5 million population

Steps of YLL Estimation

YLL Estimation

• Number of Deaths * Life Expectancy at Each Age Band• Count Total # Deaths in a Year and Assign Unique Cause• Number of Deaths Come From:

– Vital Registration Systems– Mortality Surveillance Systems– Census– Surveys– Hospital and Police Records– Verbal Autopsies and Data from Mortuary

• Life Expectancy at Each Age Band is Maximized and is set at ~ 86 years for Males and Females

Estimation of YLD

• Prevalence of Sequela * Disability Weight

Sequelae

DISEASES in HIERARCHY

Diseases Lead to Specific Conditions, known as Sequelae (singular: Sequela)

Many Diseases Have Multiple Sequelae which are grouped under “Health States”, such as Anemia due to Malaria and Dengue, has been classified into mild, moderate, and severe Anemia. These are estimated as well

DALYs For Males, GBD 2010

AGE-WISE DISTRIBUTION of DALYs, Women, GBD 2010

Change in the DALYs Between 1990 - 2010

Let’s Start Playing with the Data:

http://www.healthmetricsandevaluation.org/gbd/visualizations/gbd-insight