Determinants of health-related quality of life in multiple sclerosis: the role of illness intrusiveness

The relationship between the cognitive and physical aspects of multiple sclerosis (MS) and health-related quality of life (HRQL) was examined with particular focus on illness intrusiveness as a mediator of this relationship. Disease severity, cognitive functioning, HRQL, depression, and illness intrusiveness were assessed in 90 patients with MS. Disease severity (Expanded Disability Status Scale [EDSS]) predicted physical aspects of HRQL (SF-36 Physical Component Summary [PCS], fatigue, and bladder control). Information-processing speed (Paced Auditory Serial Addition Test [PASAT]) predicted mental and emotional aspects of HRQL (SF-36 Mental Component Summary [MCS]). However, both the EDSS and the PASAT predicted depression. Illness intrusiveness was significantly correlated with all indicators of HRQL Illness intrusiveness also mediated the manner in which disease severity predicted: physical health, fatigue, and depression. Results underscore the need to assess MS and its impact more broadly rather than relying on traditional mobility-centered assessments. While in most cases physical indices of disease predict physical quality of life and cognitive assessments predict mental and emotional quality of life, the individual's perception of MS is also a major factor contributing to quality of life. MS clearly affects multiple aspects of life and activity, as illustrated by the broad and powerful network of relationships between illness intrusiveness and all aspects of HRQL Perceptions of illness intrusiveness appear to be a central and essential measure of the impact of MS on HRQL.