Causes of individual differences in health-related quality of life according to the EQ-5D questionnaire: A twin tale of two countries

The EQ-5D is among the most widely used questionnaires for measuring subjective health-related quality of life (HRQOL). Its descriptive system comprises five dimensions (Mobility, Self-Care, Usual activities, Pain/Discomfort... [ view full abstract ]

The EQ-5D is among the most widely used questionnaires for measuring subjective health-related quality of life (HRQOL). Its descriptive system comprises five dimensions (Mobility, Self-Care, Usual activities, Pain/Discomfort and Anxiety/Depression). The score on the five dimensions can be combined into a single summary index (SSI), representing the social value of EQ-5D health states. Additionally, the questionnaire includes a visual analogue scale (VAS), measuring the subjective health perception of the respondent. However, little is known about genetic and environmental influences on individual differences in the five health dimensions and the two scales (VAS and SSI) comprising the questionnaire. The present study aimed to explore causes of variation in the EQ-5D in two large population based twin samples in Sweden and Spain with a combined sample of more than 20,000 twin individuals. Results showed that although there were slight cohort-related differences on the phenotypic level, heritability estimates were comparable across countries and dimensions, ranging between .27 and .43; which is within the range of previously reported estimates for similar constructs from other HRQOL/QOL questionnaires or self-rated health analyses. While heritability of self-rated health, assessed through the visual analogue scale (VAS), was very similar in both samples, there was some indication for a somewhat lower heritability for the single summary index (SSI), representing the social value of EQ-5D health states, in the Spanish sample (27%) as compared to the Swedish sample (43%). Possible implications and potential explanations for the present findings are discussed in detail.