Disability-adjusted life years analysis: implications for stroke research

Stroke is a prototype disorder that disables as well as kills people. The disability-adjusted life years (DALY) metric developed by the World Health Organization to measure the global burden of disease integrates healthy life years lost due to both premature mortality and living with disability. Accordingly, it is well suited to stroke research. The DALY has previously been applied only to large but relatively crude population-level data analyses, but now it is possible to calculate the DALY lost in individual stroke patients. Measuring each patient's stroke outcome with DALY lost has expanded its application to the analysis of treatment effect in acute stroke trials, delineating the poststroke complication impact, the differential weighting of discrete vascular events, and estimating a more refined stroke burden in a specific population. The DALY metric has several advantages over conventional stroke outcome measures: 1) Since the DALY measures the burden of diverse health conditions with a common metric of life years lost, stroke burden and benefits of stroke interventions can be directly compared to other health conditions and their treatments. 2) Quantifying stroke burden or interventional benefits as the life years lost or gained makes the DALY metric more intuitively accessible for public and health system planners. 3) As a continuous, equal-interval scale, the DALY analysis might be statistically more powerful than either binary or ordinal rank outcome analyses in detecting the treatment effects of clinical trials. 4) While currently employed stroke outcome measures take one-time snapshots of disability or mortality and implicitly indicate long-term health impact, the DALY explicitly indicates the burdens of living with disability for an individual's remaining life.