Burden of Disease and its DeterminantsBurden of Disease and its Determinants

By Dr Zahid Khan,

King Faisal University.

By Dr Zahid Khan,

King Faisal University.

Learning ObjectivesLearning Objectives

To get familiar with Burden of disease and concept behind this.

To understand the measurement of BOD in terms of DALYS & QALY.

To understand the Population perspective of BOD and the various determinants in BOD at population level.

To get familiar with key concepts and definitions like Life Expectancy, DALYS, QALYS, Standardized mortality rates.

Population PerspectivePopulation Perspective

Starting Point. For Looking For Doing

Population Impact Community diagnostics ( Looing at the problem). Community interventions ( acting to improve).

From that Groups with Particular risks: Disadvantaged people Elderly People Working Population Young People

What defines a Population?What defines a Population?

Catchment Area e.g Dammam city of Saudi Arabia.

Specific Unit e.g Gender, Ethnicity, marital Status, Age etc.

Specific Period.

Burden of Disease Community DiagnosticsBurden of Disease Community Diagnostics

Simple Measures of Disease. Incidence rates: Count of New cases over a period of

time. Two key formulae are:

New cases / Population at risk. New cases / Time spent by the study population at

risk.

e.g the incidence rate of this disease is 5/1000 per year.

Burden of Disease Community DiagnosticsBurden of Disease Community Diagnostics

Prevalence Rates: Count of cases ( both old and new) at a point in time in a population.

Obtained from cross sectional studies or disease registers. The formula is:

All Cases / Population at risk. e.g the prevalence of dialysis among 65-74 years old is 4

/ 10,000.

Burden of Disease Composite measuresBurden of Disease Composite measures

This comprise additional characteristics like Standardised Rate ( SMR). Adjustment of age specific

mortalities to a typical population. Life Expectancy: Adjustment of age specific mortality

to a virtual life course. Quality and Disability Adjusted Life years: reweighing

the life you live to its quality.

Standardised Mortality ratesStandardised Mortality rates

Its aim is to provide rates that can be compared with others e.g mortality rates of Saudi Arabia are higher/ lower than Qatar so you have two answers, either lower or higher. SMR for an African city is given below.

Standardised Mortality rates/ ratio.Standardised Mortality rates/ ratio.

SMR = 11,000/ 4,150 = 2.65

Age Population #Deaths (Obs)

#Deaths (Exp)

Death Rate

0 to 14 250,000 2500 250 0.01

15 to 24 200,000 2000 200 0.01

25 to 44 200,000 2000 400 0.01

45 to 64 100,000 2000 800 0.02

65+ 50,000 2500 2500 0.05

Total 800,000 11,000 4,150 0.0138

Life Expectancy RatesLife Expectancy Rates

Integration of age-specific mortality rates. Life expectancy will never be actually lived, except in a

steady state of mortality. Life expectancy at birth by race and sex, United States

Burden of Diseases: Composite MeasuresBurden of Diseases: Composite Measures

QALY & DALY: Are All years equal?No, one year of illness can affect your remaining

life.e.g 1 years with a severe Alzheimer, which destroys

your short term memory and your personality , and makes you totally care dependent!!!!

1 years being blind!!!Now compare the above two with one year of

perfect health!!!

DALY backgroundDALY background

DALY = YLL + YLDDALYs are Disability Adjusted Life Years and are

for a specific disease.YLL = Years of life lost due to dying from the

diseaseYLD = Equivalence –years of healthy life lost due

to disability because of the disease.Time is used as common Metric for mortality and

health states.

DALYsDALYs

Years you might have lived in addition if you had not had a specific disease.

DALY = YLL + YLDYLL (due to a specific disease) = N * L(x)YLL = Years of life lost due to premature

mortality.N = Number of deaths in the populationL(x) = Standard life expectancy at age of deathX = Age of death.

DALYsDALYs

YLL example. 3 deaths at age 50 and total life expectancy is 84

years.3 * 34 years life expectancy = 102 YLL

DALYsDALYs

DALY = YLL + YLDYLD = Years lived with DisabilityYLD = I * DW * dI = Number of incident cases in the populationDW = Disability weightd = Duration of disability [years] (until a specified

age)

DALYsDALYs

YLD example.4 cases of mild mental retardation due to lead at

birth 4 * 0.36 * 80 years = 115 years of life lost.Disability weight = 0.36Life expectancy = 80 yearsNumber of cases = 4

Type of Determinants at population levelType of Determinants at population level

Lalonde,s Health Field Concept.

Type of Determinants at population levelType of Determinants at population level

Where we need to focus now???Where can we find maximum benefit!!!!!Depends on the way that you look: what is a cause

(determinant).For each Determinant

What is the prevalence? What is its causative power (risk ratio)?

Maximum Profits: exampleMaximum Profits: example

Smoking:30% smokes (0.3)Risk ratio for lung cancer, if smoking : 20So, all risks for lung cancer combined:0.7 * 1 + 0.3 * 20 =0.7 (non-smokers0 + 6.0 (smokers) = 6.7Thus share of tobacco smoking in lung cancer = 6.0/6.7 = 90%This is the population attributable risk/fraction.

Summary of key points.Summary of key points.

Burden of Disease in terms of Prevalence and incidence.

BOD represented best by DALYs & QALY Determinants of Burden of Disease at

Environment ( social, physical), Human Biology, Health care organization, Life style levels.

Intervention is needed where maximum benefits are achieved in terms of determinants for a disease.

ReferencesReferences

http://www.youtube.com/watch?v=5Lul6KNIw_8 http://www.businessinsider.com/huge-racial-gap-in-life-expec

tancy-2014-1#ixzz2yLeaI62y http://www.youtube.com/watch?v=QUivL3y8Jzk#t=167

Thank You

Any Questions !!!!