Population norms for health-related quality of life and distributional heterogeneity in differences between EQ-5D-5L utility index and EQ VAS score: a large-scale cross-sectional study

The EQ-5D-5L is widely used to measure health-related quality of life (HRQoL). Updated EQ-5D-5L population norms for central China are lacking after the COVID-19 pandemic, and the relationship between the utility index and the EQ visual analogue scale (EQ VAS) score remains incompletely understood, particularly whether the factors associated with their difference vary across the distribution. This study aimed to update EQ-5D-5L population norms for adults in central China and to identify factors associated with the difference between the utility index and the EQ VAS score across the distribution. Data were drawn from the 2023 National Health Services Survey (NHSS) conducted in Hubei and Henan provinces in central China. The analytic sample comprised 20,192 community-dwelling adults aged 16 years or older. HRQoL was assessed using the EQ-5D-5L, and the utility index was calculated using the Chinese value set. An individual-level difference score was calculated as the utility index minus the rescaled EQ VAS score (EQ VAS score/100). Quantile regression models were fitted at the 10th, 25th, 50th, 75th, and 90th quantiles of the distribution of difference scores to examine associations with sociodemographic, lifestyle, and health-related factors. The mean utility index was 0.950 (SD 0.145; median 1.000), and the mean EQ VAS score was 78.59 (SD 16.36; median 80.00). The utility index reached the ceiling (1.000) in 71.3% of participants, whereas only 10.6% of them had an EQ VAS score of 100. Pain/discomfort (PD) and anxiety/depression (AD) were the most frequently reported problems, whereas self-care (SC) was least affected. Difference scores were positive for 85.9% of participants and negative for 4.2%, with a median of 0.155. Associations between participant characteristics and the difference score varied across quantiles. Older age, insomnia, and chronic conditions were associated with larger differences, and these associations were generally more pronounced at the middle and upper quantiles. This study provides updated EQ-5D-5L population norms for adults in central China based on post-pandemic data. The utility index and the EQ VAS score capture related but distinct aspects of health and should be treated as complementary rather than interchangeable measures in population surveys, particularly among older adults and people with insomnia or chronic conditions.