Calculating DALYs: UVR and skin cancer

The text on this page is taken from an equivalent page of the IEHIAS-project.

As part of the EU-funded INTARESE project, which contributed to the development of this Toolbox, a case study was conducted to assess health impacts due to skin cancer associated with ultra-violet radiation (UVR) under different climate change scenarios.

Health impacts were assessed in terms of disability-adjusted life years (DALYs).

The DALY is a health gap measure that combines both time lost due to premature mortality and non-fatal conditions. The DALY combines in one measure the time lived with disability and the time lost due to premature mortality. DALYs for a disease or health condition are calculated as the sum of the years of life lost due to premature mortality (YLL) in the population and the 'years lived with disability' (YLD) for incident cases of the health condition.

• YLL: The YLL is calculated by combining the mortality due to the health condition with the expected life expectancy for each age(group).The WHO’s Global Burden of Disease (GBD) study (WHO 2008; Mathers et al 2001) used the same life expectancy ‘ideal’ standard for all population subgroups, whether or not their current life expectancy is lower than that of other groups. To define this Standard Expected Years of Life Lost (SEYLL), the highest life expectancy observed for any nation (i.e. the 82.5 years life expectancy of women in Japan) was chosen. The standard expectations are therefore based on a model life table, namely Coale and Demeny West level 26, which have a life expectancy at birth for females of 82.5 years. Following the WHO GBD-study (WHO 2008) and the 2001 Victorian Burden of Disease study (DHS 2005), WP3.7-UVR uses this standard life expectancy for calculating YLL.
• YLD: Years lived with disability (YLD) are the disability component of DALYs that describe the time spent with a disease or injury for a specified duration, adjusted for severity. The YLD uses explicit preference weights for health states. Hence, the severity of a diseases is indicated with disability weights (DW), expressed on a scale from zero to one, with zero being full health/no disability and one representing death.

As part of the assessment of UVR and skin cancer, data on skin cancer incidence and mortality (for the baseline, SRES-B1 2030 and SRES-A2 2030 scenarios) were translated into DALYs.

Table 1: DALY basics

DALY = YLL + YLD YLL = years of life lost due to premature mortality YLD = years lived with disability
	YLL= N x L N= Number of deaths; L= life expectancy at age of death (in years)
YLD = I x DW x L I= incident cases; L= Average duration of disability (years); DW= Disease weight

Details of the calculation are given in the worked example in the attached spreadsheet.