The effect of educational level in the comparison of pre-injury health-related quality of life (HRQoL) with HRQoL of a Dutch reference population

Introduction/Background Differences between retrospectively collected pre-injury Health-related Quality of Life (HRQoL) data and population norms might be partly explained by differences in the distribution of educational level between cohorts. The first aim of this study was to examine whether retrospectively collected pre-injury HRQoL of the Dutch general hospitalized trauma population, is identical to HRQoL of a representative sample of Dutch individuals stratified by age, gender and educational level. Second, we examined the role of educational level in this comparison. Material and Method This study was part of a longitudinal survey among trauma patients admitted to the hospital between August 2015 and November 2016. Pre-injury HRQoL was collected by using the EuroQol-5D-3L (EQ-5D-3L) questionnaire. The reference cohort compromises a representative sample of the Dutch population. HRQoL was compared between the injury cohort (n = 3032), reference cohort (n = 1839) and general population norms by using descriptive statistics. The effect of educational level in the comparison between the injury cohort and reference cohort was investigated by entering educational level in the multiple regression model after age and gender. Outcome measures were EQ-5D-3L tarif, EQ-VAS and the five domains of the EQ-5D-3L. Results In general, the injury cohort reported better recalled pre-injury HRQoL compared to the HRQoL of the reference cohort and compared to the general norm population after adjustment. The ≥10% increment of the Beta after the addition of educational level in the multiple regression analysis suggested that educational level is a confounder for HRQoL. Conclusion Even after adjustment for age, gender and educational level trauma patients report a better pre-injury HRQoL score compared with the HRQoL of the reference cohort. To make a reliable comparison between an injured cohort and a reference group it is strongly advisable to adjust for educational level besides age and gender.