How is ypll different from dalys

Sassi, F. Health Policy and Planning, 21 5 , What is a DALY? YLL is calculated as the number of deaths n x the standard life expectancy at age of death L1. This measures the reduction in life expectancy. YLD is the number of new cases of a disease I x a disability weight DW x the average time a person lives with the disease before remission or death L2.

This measure represents the diminished quality of life experienced for an individual with injury or illness. Video credit: Kahn JG. For example, if a new treatment gave an additional 0.

The DALY is an alternative tool which emerged in the early 90s, as a means of quantifying the burden of disease. YLL are calculated as the number of deaths at each age multiplied by the standard life expectancy for each age.

As an example, a woman with a standard life expectancy of If she additionally turned blind at aged 45, this would add 5 years spent in a disability state with a weight factor of 0. In total, this would amount to The weight factors are age-adjusted to reflect social preference towards life years of a young adult over an older adult or young child. Furthermore, they are discounted with time, thus favouring immediate over future health benefits. The two measures can produce different results dependent on age at onset and duration of disease, and whether age and disability are weighted.

QALYs and the DALYs can be applied to a wide range of diseases and interventions in different population settings, however both face criticisms. Neither measure fully captures the wider effects that stem from interventions: emotional and mental health, impact on carers and family, or non-health effects such as economic and social consequences e. QALYs can lack sensitivity and may be difficult to apply to chronic disease and preventative treatment.

Disease-specific measures may be used, but must be interpreted with caution. A life table is a table which shows, for a person at each age, what the probability is of them dying before their next birthday. From this starting point, a number of statistics can be derived and are also included in the table:. Life tables are usually constructed separately for men and for women because of their substantially different mortality rates.

The Office of National Statistics is one organisation which produces life tables. Age specific mortality rates are applied to a notional population, typically of , an example is the European Standard population.

Starting at birth, the probability of dying in each period is applied to the number of people surviving to enter that period, so that the initial figure slowly reduces to zero. This sort of life table is based on current age-specific death rates for each age or age band used and are called 'period life tables' and are the most frequently used type. In contrast, actual life expectancy of a particular birth cohort can only be calculated when everyone in this cohort is dead.

This is called a 'cohort life table' and requires data over many years to prepare just a single complete cohort life table.

An example of how a life table can be constructed and the mathematics involved can be downloaded from the simple interactive statistical analysis website. It does not say much about who is still alive, and their quality of life; for example, how many years are lived with disability before dying.

This has led to attempts to bring together morbidity and mortality, with measures such as Health Adjusted Life Expectancy and Disability Adjusted Life Years. Other characteristics can also be used to distinguish different risk factors for life expectancy, such as smoking-status, occupation, socio-economic class, and others. More complex analyses for assessing cancer survival, that involve comparisons between two populations or a population at two points in time can also be undertaken.

In addition to public health domains, life tables are also used by insurance companies and actuary departments. When data have not been available, such as in low income countries, life tables have been modelled using what data are available, usually childhood mortality data.

HALE is a measure of population health that takes into account mortality and morbidity. It adjusts overall life expectancy by the amount of time lived in less than perfect health.