The U.S. Center for Disease Control and Prevention (CDC) defines health-related quality of life (HRQoL) as “an individual’s or a group’s perceived physical and mental health over time.” The various tools used to measure HRQoL get at physical, mental, emotional, and social functioning. HRQoL assessments can, in turn, yield important burden of disease information on the quality of relationships, expressed emotions and resilience, realization of potential, and level of overall satisfaction with life. As with any clinical assessment tool, issues of sensitivity, reproducibility, and validity for use in a given population are important to discern.

Health-Related Quality of Life in DM1

A new report in the journal, The Patient—Patient-Centered Outcomes Research, undertook a literature review of HRQoL in adult-onset DM1, focusing on 19 publications meeting selection criteria. The resulting burden of disease conclusions should help inform patient families, researchers, drug developers, public policy experts, and regulatory authorities.

The DM1 HRQoL study was undertaken by Dr. Erik Landfeldt (Karolinska Institutet and ICON plc) and colleagues (Landfeldt et al., 2019). The team sought to determine the geographic focus of and instruments used in studies of adult-onset DM1 HRQoL, and to report a synthesis of findings from a meta-analysis of eligible studies. Study search and selection criteria followed established guidelines for such analyses (PRISMA), starting with all articles found in Embase, Web of Science, and PubMed and filtering based upon publication year (since 2000), language (English), cohort size (excluding reports of ≤ 5 subjects), and publication type (excluding reviews and op/eds). Starting with 266 unique publications from keyword-based literature searches, 19 articles met criteria for inclusion in the meta-analysis.

The geographic focus of the DM1 HRQoL studies included 8 countries in Europe, North America, or South America. The instrument used by most was SF-36 (n = 19), with INQoL (n = 6) and Cantril’s Ladder (n = 1) also used.

The majority of studies reported that all SF-36 subscale scores were lower in adult-onset DM1 than in control populations (2 studies reported lower physical health, but not mental health, scores). Considerable cross-study heterogeneity in mean reported values, subtending much of the 0-100 SF-36 range, was observed for many subscale scores—including physical functioning (scores ranged from 38 to 82), role physical (from 22 to 95), and role emotional (from 28 to 96). Similar heterogeneity in reported scores was seen for studies using the INQoL instrument.

Finally, the Cantril’s Ladder used in one study evaluated here reported a mean HRQoL score that was not different from that of health relatives or unaffected family members, suggesting it was the least useful measure for this purpose.

Conclusions

Although two instruments (SF-36 and INQoL) have been used extensively in adult-onset DM1, a concerning level of heterogeneity in mean scores was seen across the 19 studies used in the analysis reported here. Whether this reflects variability in the cohorts evaluated in the different studies or flaws in the HRQoL assessment instruments is unclear. A deeper analysis of the patient populations assessed in individual studies (e.g., assessing, when possible, the placement of patients on the DM1 spectrum as identified by De Antonio et al., 2016) might yield underlying explanations for the high degree of heterogeneity. The study team also suggests the operation of demographic, cultural, or instrument psychometric properties as explanations for the high degree of variability. Questions about whether these instruments had been sufficiently validated for use in DM1 must be answered if they are to be of value for natural history studies or interventional clinical trials.

References:

Health-Related Quality of Life in Patients with Adult-Onset Myotonic Dystrophy Type 1: A Systematic Review.
Landfeldt E, Edström J, Jimenez-Moreno C, van Engelen BGM, Kirschner J, Lochmüller H.
Patient. 2019 Feb 4. doi: 10.1007/s40271-019-00357-y. [Epub ahead of print] Review.

Unravelling the myotonic dystrophy type 1 clinical spectrum: A systematic registry-based study with implications for disease classification.
De Antonio M, Dogan C, Hamroun D, Mati M, Zerrouki S, Eymard B, Katsahian S, Bassez G; French Myotonic Dystrophy Clinical Network.
Rev Neurol (Paris). 2016 Oct;172(10):572-580. doi: 10.1016/j.neurol.2016.08.003. Epub 2016 Sep 21.