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Approaches to Measuring Population Health Ian McDowell March, 2010. Mortality-based summary measures Combined disability & mortality methods Conceptual rationale for summary measures Environmental indicators Global indicators. EPI 5343. 1. Why do we need measures of population health?.
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Mortality-based summary measures
Combined disability & mortality methods
Conceptual rationale for summary measures
Governments wish to monitor health of citizens
Note: this figure shows the typical blend of methods you might use in a particular type of study: HSR would use descriptive and evaluative, for example.
Morgenstern H. Ecologic studies in epidemiology: concepts, principles, and methods. Annual Reviews of Public Health 1995; 16:61-81.
Linking the target of a population intervention to the type of measure Interventions can target people, environmental factors, or policy in general
These correspond to Morgenstern’s categories of measures used to evaluate the intervention…
…and to the
Expected years of life lost
Potential years of life lost
What types of individual measure can be meaningfully aggregated?
Can you make an index out of
This diagram extends the earlier one by recognizing that not all survivors are perfectly healthy.
The lower area ‘H’ shows the proportion of people in good health (however defined); it shows healthy life expectancy. The top curve shows deaths; intermediate area represents levels of disability.
Area ‘G’ again represents the health gap. The question arises whether the people with a disability ought to be counted with H or with G.
M F M F
The area ‘H’ again includes healthy people - although the definition may have changed. The top curve shows deaths; intermediate curves represent three levels of disability. Each will have a different severity weighting.
Poor people not onlydie earlier, but alsoexperience moredisability than richerpeople.
HLE: Healthy Life
By down-weighting the
various levels of disability,
the HALE falls between
LE and HLE
Full Health Partial Health Premature mortality
Death among these patients
(Stage and Severity)
Years of Life Lost due to premature mortality
Year Equivalents of life lost due to Reduced Functioning
= Health Adjusted Life Years lost
(YLL + YERF)
Standard Life Expectancy (SLE)
Standard Expected Years of Life Lost (SEYLL)
Health-Adjustedor Disability-AdjustedLife Yearslost (HALYs or DALYs)
Health gap measures
Mean Life Expectancy(LE)
Years Lived withDisability (YLD)
Health-Adjusted, orDisability-AdjustedLife Expectancy (HALE or DALE)
Health expectancy measures
Healthy LifeExpectancy (HLE), or Disability-Free Life Expectancy (DFLE)
Towards a Functional Classification
Source: John Ware, October 2000
Compositional vs. Contextual Measures
Some environmental variables have no individual counterpart:
Air quality (SO2)
Road traffic density
Composite Indicator, including:
High school drop-out rate
Avg. weekly earnings
Seniors’ poverty rate
Uninsured health costs for seniors
Source: Human Resources Development CanadaApplied Research Bulletin 1997;3:6-8
L(s) lies below line of equality when income inequality favours the rich
Gini coefficient is twice the area between the curve and the line of equality
% of population
L(s) lies above line of equality when ill-health is concentrated among poor.
L*(s) is indirectly standardized curve indicating unavoidable inequality (e.g., due to age-sex distribution)
Inequality favours rich if L(s) lies above L*(s)
Cum % of
Cum. % of population
ordered by income
Multiply mean by concentration index [L(s) in previous slide].
E.g., in diagram at right, U5 mortality for India is lower than Bangladesh.
But in India mortality is concentrated among poorer people more than in Bangladesh; concentration index is -0.169, compared to -0.084 for Bangladesh. So achievement index = mean x 117% = 139.
Resulting achievement index is equal for the two countries.Achievement Index (Wagstaff, 2001)
Mean Under 5 Mortality Rate, and Achievement Index for India andBangladesh