Global burden of disease (GBD) - How to measure disease burden and importance of risk factors

Global burden of disease (GBD) - How to measure disease burden and importance of risk factors Emilie.agardh@ki.se

Measuring burden of disease What is burden of disease? Why measure burden of disease? How to measure burden of disease? The burden of disease in different countries The importance of risk factors to the burden of disease

Diseases/diagnoses There are approx 137 different disease diagnoses Different interest groups emphasize different diseases as major public health problems With limited resources within health care, how and which diseases should be given priority?

Global Burden of Disease (GBD) WHO-project During the past decade, WHO and the World bank have carried out a project with the aim to develop one measure on the global burden of disease This was the origin to the Global Burden of Disease Project (GBD) (published first time in the World Development Report, Investing in Health 1993).

What is burden burden of disease?

A measurement of the gap between the current health of the population and an ideal situation where everyone in the population lives in old age in full health.

Summary measures of population health (SMPH) Measures of population health that combines information about both mortality and disability into a single number

Global Burden of Disease (GBD) WHO-project Several different methods and measures were introduced to measure burden of disease in the GBD-project HALE, QALY, etc The main measure that was used was DALY = Disability Adjusted Life Years

Why measure burden of disease?

With a combined measure of population health it is possible to: Compare health in a population over time or between different populations Identify and quantify inequalities Provide appropriate and balanced attention to non-fatal health outcomes Inform debates on priorities for health service delivery, planning, prevention etc.

Using DALY to measure burden of disease

DALY (Disability adjusted Life Years) DALY is a combined measure on the disease burden that describes ill health in the population by combining information about both mortality and disability

DALY Most frequently used to measure burden of disease What specifically is measured is the time (years) with optimal health that is lost due to: Premature death Lost of function (disease)

The two basic components in DALY is thus: YLL (Years of Life Lost) 1 YLL = one year lost due to premature death YLD (Years of Lost due to Disability) 1 YLD = one year lost due to, disability

To define lost years.. The highest observed life expectancy for any nation was chosen i.e., Japan. With a life expectancy: 82.5 years for women With a life expectancy: 80 years for men

Which data are needed to calculate DALY? Population: Age, sex, life expectancy Mortality, distributed by age and sex and cause of death Epidemiological data (incidence and duration) on nonfatal disease, distributed by age and sex Valuation of disability (disability weight)

Valuation (weighting) of disability (DW) Valuation of how difficult the loss of function is presumed to be (used for YLD).

Valuation (weighting) of disability (DW) One example is a scale, i.e., Disability is graded on a scale 0-1, 0= No disability, complete health, 1=Complete disability, death

Valuation (weighting) of disability (DW) One example is a scale, i.e., Disability is graded on a scale 0-1, 0= No disability, complete health, 1=Complete disability, death

Valuation (weighting) of disability (DW) Complete health 0 0.2 0.4 0.6 0.8 Death 1 *Severe depression *Cold *Amputation of a leg *Blindness *Severe asthma *Deafness

DISCUSSIONS Grade the different diseases on a scale between 1- and 0 Think- you will have this condition during one day (but you do not know for how long it will last). Loss of function handicap

Have in mind: loss of function The limitation a disease and injury bring to the ability to function normal is The same for all people Loss of function handicap Ex. An amputated leg is valuated the same in DALY irrespective of being a farmer in Indonesia or an office worker in Sweden

Who should make these values?

How is YLL calculated? YLL = Years of life lost due to premature death The calculation of YLL for a specific diagnose (distributed by age and sex), is made by multiplying number of deaths with life expectancy at point when death occur. Where; N = number of deaths L= Life expectancy YLL = N * L

How is YLD calculated? YLD = Years of Lost due to Disability The calculation of YLD for a specific diagnose (distributed by age and sex) is made by multiplying the incidence (I) with expected time to recovery or death (L) with disability weight (0-1). YLD = I * L * DW Where; I = Number of incident cases L= Expected time to recovery or death (duration) DW = Disability weight

How is DALY calculated? YLL + YLD = DALY

How is DALY calculated? YLL + YLD = DALY

Calculating DALY (example individual level) Example 1: A man who is completely healthy and dies 80 years old. 0 YLD 0 DALY 0 YLL, Complete 0 health Death 1 80 years

Calculating DALY (example individual level) Example 2: This man gets a knee injury at the age of 60 (before this he is completely healthy) and needs to amputate his leg. At the age of 80 he dies. 6 YLD, 0 YLL, 6 DALY Complete 0 health *DW (amputation) = 0.3 *Healthy years lost= 20 YLD = 0.3 X 20 =6 Death 1 60 80 years

Calculating DALY (example individual level) Exempel 3: A man who is completely healthy and dies at the age of 75 years in coronary heart disease. 5 YLL, 0 YLD, 5 DALY Complete 0 health *Years of life lost due to premature death= 5 YLL =5 Death 1 80 years

Calculating DALY (example individual level) Example 4: A man suffers from severe depression at the age of 20 years old. At the age of 30 he is cured. At the age of 50 he is involved in an accident and becomes blind on both eyes. At the age of 65 years he dies in a stroke. 21.2 YLD, 15 YLL, 36.2 DALY Complete 0 health Death 1 DW for; *severe depression =0.83 *blindness = 0.43 Healthy years lost due to; *severe depression = 10 *blindness = 30 *years of life lost due to premature death = 15 YLD = 0.83 X 10 + 0.43 X 30=21.2 YLL = 15 80 years

DALY a population measure DALY is a population measure Enables to calculate the total sum of the combined loss of all premature deaths and loss of healthy life from disability from specific diseases world wide

Diagnose criteria's YLL and YLD can be summarized for all disease categories and subcategories in order to obtain one DALY measure for; example neuropsychiatric conditions, coronary heart disease, cancers etc.

Ex: Neuro-psychiatric disease Men DALY YLL YLD Neuro-psychiatric disease 154569 33551 121018 Unipolar depression 28926 155 28771 Bipolar affective disease 6284 0 6284 Schizophrenia 8142 101 8041 Epilepsia 3916 2245 1670 Alcohol addiction 28132 9017 19115 Dementia 37255 9763 27492 Parkinson 5527 1553 3974 Multiple sclerosis 1847 864 1010 Narcomania 6797 4756 2041 Post traumatic stress syndrom 869 0 869 Tvångssyndrom 1836 0 1836 And a few more..

What are the benefits with a summary measure of population health that measure both mortality and disability at the same time?

How would you share the health-care resources if you had the following information?

Year of life lost due to premature death (YLL) Sweden 2002, women YLL women Sjukdomar i ögon och öron Tandsjukdomar Graviditet och förlossning Hudsjukdomar Näringsbrist Endokrina sjukdomar Perinatala tillstånd Övriga tumörer Muskuluskeletala sjukdomar Sjukdomar i urin- och könsorgan Infektioner Medfödaa missbildningar Diabetes Luftvägsinfektioner Mag-tarmsjukdomar Sjukdomar i luftvägarna Skador Neuro-psykiatriska sjukdomar Maligna tumörer Hjärtkärlsjukdomar YLL 0 20000 40000 60000 80000 100000 120000 140000 160000

Years of Life lost due to disability (YLD) Sweden 2002, women YLD, women Sjukdomar i ögon och öron Tandsjukdomar Graviditet och förlossning Hudsjukdomar Näringsbrist Endokrina sjukdomar Perinatala tillstånd Övriga tumörer Muskuluskeletala sjukdomar Sjukdomar i urin- och könsorgan Infektioner YLD Medfödaa missbildningar Diabetes Luftvägsinfektioner Mag-tarmsjukdomar Sjukdomar i luftvägarna Skador Neuro-psykiatriska sjukdomar Maligna tumörer Hjärtkärlsjukdomar 0 20000 40000 60000 80000 100000 120000 140000 160000 180000 200000

Burden of disease (DALY) Sweden 2002, women DALY(0,0) Kvinnor 0 50000 100000 150000 200000 250000 Infektioner Luftvägsinfektioner Perinala tillstånd Näringsbrist Maligna tumörer Övriga tumörer Diabetes Endokrina sjukdomar Neuro- Psyk. Ögon och öron Hjärt- kärl. YLL(0,0) YLD(0,0) Luftvägar Mag- tarm Urin- och könsorgan Hud Muskoloskeletala Medfödda missbildningar Tandsjukdomar Skador Graviditet och förlossning

Year of life lost due to premature death (YLL) Sweden 2002, men YLL Tandsjukdomar Sjukdomar i ögon och öron Hudsjukdomar Näringsbrist Muskuluskeletala sjukdomar Övriga tumörer Endokrina sjukdomar Perinatala tillstånd Sjukdomar i urin- och könsorgan Infektioner Medfödaa missbildningar Diabetes Luftvägsinfektioner Sjukdomar i luftvägarna Mag-tarmsjukdomar Neuro-psykiatriska sjukdomar Skador Maligna tumörer Hjärtkärlsjukdomar YLL 0 20000 40000 60000 80000 100000 120000 140000 160000 180000 200000

Years of Life lost due to disability (YLD) Sweden 2002, men YLD Tandsjukdomar Sjukdomar i ögon och öron Hudsjukdomar Näringsbrist Muskuluskeletala sjukdomar Övriga tumörer Endokrina sjukdomar Perinatala tillstånd Sjukdomar i urin- och könsorgan Infektioner Medfödaa missbildningar YLD Diabetes Luftvägsinfektioner Sjukdomar i luftvägarna Mag-tarmsjukdomar Neuro-psykiatriska sjukdomar Skador Maligna tumörer Hjärtkärlsjukdomar 0 20000 40000 60000 80000 100000 120000 140000

Burden of disease (DALY) Sweden 2002, men DALY(0,0) Män 0 50000 100000 150000 200000 250000 Luftvägsinfektioner Infektioner Perinatala tillstånd Näringsbrist Maligna tumörer Övriga tumörer Diabetes Endokrina sjukdomar Neuro- psyk. Ögon och öron Hjärt- kärl. YLL(0,0) YLD(0,0) Luftvägar Mag- tarm Urin- och könsorgan Hud Muskoloskeletala Medfödda missbildningar Tandsjukdomar Skador Graviditet och förlossning

Which risk factors contributes to the burden of disease?

Comparative Risk Assessment (WHO-project) Continuation of the GBD-project The challenge: To compare a number of risk factors and estimate the importance of their influence on the disease burden.

Why include risk factors? Disease data is focused on curative needs Risk factors are possible to prevent Important for preventive measures Basis for prioritization and planning of health political measures

Selected risk factors In total 26, mainly medically defined risk factors Probability of being among the leading causes to the disease burden High probability for causality Possible to modify Access to reasonable complete data

Risk factors, examples Childhood and maternal malnutrition Underweight Iron deficiency Diet and physical activity Overweight High cholesterol Addictive substances Tobacco Alcohol

Results, low-income countries (WHO 2002) Men (%DALY) Women (%DALY) Underweight 14,9 Unsafe sex 9,4 Unsafe water/san 5,5 Indoor smoke 3,7 Zinc deficiency 3,2 Tobacco 3,4 Alcohol 2,6 Underweight 15,0 Unsafe sex 11,0 Unsafe water/san 5,6 Indoor smoke 3,7 Iron deficiency 3,5 Vit A deficiency 3,5 Zinc deficiency 3,2

Results, high-income countries (WHO 2002) Men (%DALY) Women (%DALY) Tobacco 17,1 Alcohol 14,0 Blood pressure 11,2 Cholesterol 8,0 Overweight 6,9 Fruit and veg.bles 4,3 Physical activity 3,3 Blood pressure 10,6 Overweight 8,1 Cholesterol 7,0 Tobacco 6,2 Fruit and veg.bles 3,4 Alcohol 3,3 Physical activity 3,2

Attributable fraction How much of the disease burden can be avoided if you take away a certain risk factor Need information about the Relative Risk This is the same between countries Prevalence of exposure Differ between countries

Exemple: High BMI in Sweden High BMI causes in total: 67 257 DALYs for men and 61 453 DALYs for women Corresponding to 7.6% of the total disease burden in Sweden This means that: 7.6% of the total burden of disease can be avoided if obese persons decrease their BMI

In the CRA-project, socio-economic factors are not measured The risk factors are mainly medical defined We are now working on a project to include socio-economic risk factors to investigate how this may influence the burden of disease.

So is DALY a perfect measure?

Critics against DALY DALY is an important contributor in discussions about priorities in public health questions. However: The measurement is difficult to understand immediately (not like for example mortality, prevalence of disease etc). It is controversial to value diseases (DW) There is a risk that DALY gives a seeming objectivity. The measures are based on data assumed to be reliable (but this varies a lot between countries). It is not always easy to find reliable data

Can you answer to the following questions? What is burden of disease? Why measure burden of disease? How is burden of disease measured? Why is it important to include risk factors to the burden of disease?