Preferences for health-related quality of life: do they vary by age? A systematic literature review on the EQ-5D measure

Introduction
Cost-utility analysis (CUA) is a commonly used method in Health technology assessment (HTA) that utilises generic metrics such as quality-adjusted life years (QALYs). QALY is a measure derived from individuals’ preferences for different health states, with these preferences represented as utility values. However, utility values may differ by age, raising equity concerns in healthcare allocation. Given the globally ageing demographic, understanding the age-utility relationship becomes essential.

Objectives
This systematic review aimed to explore the impact of age on utility values derived from the EQ-5D, a widely used instrument in CUA that contributes to calculating QALYs by assessing five dimensions of health: mobility, self-care, usual activities, pain/discomfort, and anxiety/depression.

Methods
Our search used the comprehensive pearl growing approach and database searching. We included studies that analysed the effect of age on EQ-5D utility values in the general population. We excluded qualitative, non-English, and non-EQ-5D instrument studies. Quality was appraised using the Joanna Briggs Institute tool, and a narrative synthesis was used.

Results
Of the 28 studies reviewed, primarily from Europe and the Americas, the average age of participants ranged from 34.1 and 47.7 years. Around 46% (n = 13) associated older age with lower utility values; 28% (n = 8) with higher utility; and 25% (n = 7) found no consistent relationship between age and utility.

Discussion
Age was identified as a critical factor affecting EQ-5D-derived utility values, with implications for the equitable distribution of healthcare resources. These findings corroborate previous research on utility measurement across different instruments, highlighting the ethical and policy issues due to age-related utility differences.