Quality of life in Duchenne muscular dystrophy: the disability paradox

In 1999, Albrecht and Devlieger used the term ‘disability paradox’ for the phenomenon that people who have serious health conditions, with lasting impairments and disabilities, can nevertheless experience a good quality of life, although this may seem counterintuitive to most external observers. In their study of a laudably large cohort of patients with Duchenne muscular dystrophy (DMD), Landfeldt et al. encountered this phenomenon once more: happy patients, with low quality of life as rated by the general public. To explain the paradox, one must ask what was asked of whom. Quality of life is about having your individual needs and desires fulfilled to a reasonable degree, feeling that life offers a balance between challenges and successes in areas that are of personal salience; about feeling that life delivers all or most of what is expected or desired. How this is operationalized in quality of life measurements differs widely between instruments used and the operationalization strongly influences outcome. Questionnaires, measuring fixed domains (functioning, health, social life) may give different results than a single-item measure (‘How do you rate your quality of life? ’) in which people can intuitively base their answer on domains that are personally salient to them. In the Landfeldt et al. study, health-related quality of life (HRQOL) (questionnaire) was related to disease progression, whereas happiness (single-item) was not. HRQOL has a narrower scope than general quality of life, referring to the impact of health and illness on physical, mental, and social domains. Here too, exactly what you measure makes a big difference. We performed a study on HRQOL in adults with DMD in which we used two measures: the Medical Outcome Study Short Form-36 (SF-36), which measures perceived states, capabilities and functioning related to health (i.e. health status), and the World Health Organization Quality of Life (WHOQOL)-BREF, which measures satisfaction with perceived states, capabilities, and functioning. On the SF-36, scores were lower than reference population scores on all domains except the psychological domains (comparable to the findings of Landfeldt et al.). However, the WHOQOL-BREF scores on the physical health, psychological health, and environment domains were at least on the same level as the reference population scores, with a lower score on only the social relationship domain. This showed that the adults with DMD were aware of their disabilities (health status), but often satisfied with the way the corresponding activities were being managed, leading to a relatively good HRQOL; better than would be expected by an outsider. Here, the matter of who you ask to evaluate HRQOL comes into the picture. In the Landfeldt et al. study, patients rated their HRQOL higher than parents and much higher than the general public. For the latter group, the difference between what is considered normal health and functioning, and the health status of patients with DMD will loom much larger, since they discount the individuals’ ability to adapt to new or evolving situations that arise from having a physical condition or disease (response shift). Elements of this adaptation are, amongst others, enhancing skills in retained physical or mental capacity, adjusting activities, adjusting goals in order to keep them achievable, but also denying realities about the objective health status. In the population with DMD, response shifts are made from an early age in an ongoing process. This may enable individuals to experience a good quality of life, their progressive disabilities notwithstanding. It is important knowing that young and adult males with DMD consider their quality of life to be relatively good because false assumptions about quality of life may negatively influence medical decisions and this knowledge may give some positive perspective to families. But to correctly interpret any findings on quality of life and to explain the disability paradox, the questions ‘What was the exact concept of quality of life measured? ’ and ‘Who was asked to evaluate? ’ are of the greatest importance.