Burden of disease and determinants of health

1. Burden of Disease and its Determinants
By Dr Zahid Khan,
King Faisal University.

2. Learning 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.

3. Population 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

4. 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.

5. Burden 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.

6. Burden 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.

7. Burden 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.

8. Standardised 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.

9. 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

10. Life 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

11. Burden 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!!!

12. DALY background
DALY = YLL + YLD
DALYs are Disability Adjusted Life Years and are
for a specific disease.
YLL = Years of life lost due to dying from the
disease
YLD = Equivalence –years of healthy life lost due
to disability because of the disease.
Time is used as common Metric for mortality and
health states.

13. DALYs
Years you might have lived in addition if you had
not had a specific disease.
DALY = YLL + YLD
YLL (due to a specific disease) = N * L(x)
YLL = Years of life lost due to premature
mortality.
N = Number of deaths in the population
L(x) = Standard life expectancy at age of death
X = Age of death.

14. DALYs
YLL example.
3 deaths at age 50 and total life expectancy is 84
years.
3 * 34 years life expectancy = 102 YLL

15. DALYs
DALY = YLL + YLD
YLD = Years lived with Disability
YLD = I * DW * d
I = Number of incident cases in the population
DW = Disability weight
d = Duration of disability [years] (until a specified
age)

16. DALYs
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 = 0.36
Life expectancy = 80 years
Number of cases = 4

17. Type of Determinants at population level
Lalonde,s Health Field Concept.


18. Type 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)?

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

20. 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.

21. References
 http://www.youtube.com/watch?v=5Lul6KNIw_8
 http://www.businessinsider.com/huge-racial-gap-in-life-expectan
 http://www.youtube.com/watch?v=QUivL3y8Jzk#t=167

22. ThankYou
Any Questions !!!!