Disability indicators
1. HALE (Health – Adjusted Life Expectancy)
2. QALY (Quality – adjusted life years)
3. Disability – free life expectancy (active life expectancy)
4. Disability – adjusted life years (DALY)
HALE (Health – Adjusted Life Expectancy)
• Previously k/a DALE (disability adjusted life expectancy)
• Indicator used to measure healthy life expectancy
• Based on life expectancy at birth BUT
o Includes an adjustment for time spent in poor health
• Definition: equivalent number of years in full health that a new-born can expect to live based on current rates of ill health and mortality
QUALY (Quality – Adjusted Life Years)
• A measure of disease burden including both:
o Quality and
o Quantity of life lived
• Used in assessing the value for money of a medical intervention
• Based on the number or years of life that would be added by intervention’
o Each year in perfect health = 1.0
o Death = 0.0
• 1 QUALY = one year of life X one utility value = one year of life lived in perfect health
• Half a year lived in perfect health is equivalent to 0.5 QUALY = 1 year X 0.5 utility value
DFLE: Disability – free life expectancy (Active life expectancy)
Average number of years an individual is expected to live free of disability if current pattern of mortality and disability continue to apply
DALY (Disability – Adjusted Life Years)
Measure of overall disease burden
Developed by Harvard University for WHO
Expressed as ‘number of years lost due to
• Ill health,
• Disability or
• Early death ’
Used as a major measure by the ‘’Global Burden of Disease Project’’
Combines the effect of important fatal and non-fatal disabling conditions through a single measure
Calculated as:
DALY = YLL + YLD
YLL = Years of Lost Life = no. of deaths at each age multiplied by the expected remaining years of life according to a global standard life expectancy (LE)
• Japanese LE is used as the global standard
• As Japanese have the longest LE
YLD = Years Lost to Disability = no. of incident cases due to injury and illness is multiplied by the
1. Average duration of the disease and
2. A weighting factor reflecting the severity of the disease on a scale from 0 to 1
• Severity score = 0 =perfect health
• Severity score = 1 = death
One DALY = one year of health life LOST
1990 WHO report revealed:
• 50% of leading causes of disability were psychiatric conditions
• Psychiatric and neurological conditions account for 28% of YLD but accounts for ONLY 1.1% of YLL
Crucial distinction of DALY is:
The use of ‘’Social Weighting” (value of each year of life depends upon the age)
Interplay between:
1. LE
2. Years lost (YLL, YLD)
3. Social weighting
Are complex, depending upon the severity and duration of illness