Factors Affecting Quality of Life in Idiopathic Inflammatory Myopathy

Multiple disease characteristics are associated with reduced quality of life and working productivity impairment among patients with idiopathic inflammatory myopathy (IIM), according to a study published in Rheumatology.

Investigators assessed health-related quality of life (HR-QOL), work productivity and activity impairment (WPAI), and their associated factors among patients with IIM.

An observational, cross-sectional study was conducted, including ambulatory patients over the age of 18 diagnosed with IIM.

The European Quality of Life 5-Dimension (EQ-5D) tool was used to evaluate quality of life, with responses aligning patients with 1 of 3 quality states: no problem, moderate problem, or extreme problem. Reponses were converted to index values ranging from -0.21 to 1.00, with higher values indicating better health. The WPAI questionnaire was used to measure impairment in work-related and health-related activities. Clinical remission was defined using the International Myositis Assessment and Clinical Studies Group criteria.

Among the 189 patients enrolled, 75% were women, 60% had dermatomyositis, 13% had polymyositis, 27% had clinical amyopathic dermatomyositis, and the median age at IIM diagnosis was 45 years.

Patients in no problem states had EQ-5D index values of 1.00, while those in remission had lower values. Among the patients enrolled, 70% reported impaired activity due to health problems, 28% were participating in paid work, 21% reported absence from work in the past week, 62% reported that their work was impaired due to their health, and 45% reported overall work productivity loss due to health problems and absence from work. 

When assessing factors associated with EQ-5D and activity impairment, diminished mobility was associated with decreased Manual Muscle Testing-8 (MMT-8) scores (odds ratio [OR], 0.975; P =.039), increased Pulmonary Myositis Disease Activity Assessment Visual Analogue Scale (MYOACT) scores (OR, 1.412; P =.006) and increased Patient Global Assessment (PtGA) scores (OR, 1.054; P <.001).

Poor self-care status was associated with decreased MMT-8 scores (OR, 0.966; P =.012), increased PtGA scores (OR, 1.061; P =.001), and increased Disease Activity Score (DAS) (OR, 1.226; P =.033).

Reduced activity status was associated with shorter disease duration (OR, 0.798; P =.025), decreased MMT-8 scores (OR, 0.963; P =.002), increased Myositis Damage Index (MDI)-global scores (OR, 1.296; P =.036), and increased PtGA scores (OR, 1.057; P =.033).

Greater pain and discomfort were associated with increased MYOACT (OR, 1.592; P =.004), MDI-global (OR, 1.363; P =.011), and PtGA (OR, 1.033; P =.001) scores. Increased PtGA scores (OR, 1.019; P =.044) were associated with worse anxiety and/or depression.

When analyzing work impairment in IIM, working patients had higher MMT-8 scores and lower DAS, MYOACT, and Physician Global Assessment (PGA)/PtGA scores, and were more likely to be in disease remission. Overall, increased MYOACT scores, active stage IIM, and increased PtGA scores were associated with increased working impairment.

Study limitations included a skewed distribution of data, leading to the use of quantile rather than traditional linear regression during analyses. Additionally, the small sample size of employed patients may have introduced bias. Finally, factors that may influence working status were not considered.

The study authors concluded “In summary, we have demonstrated that multiple disease characteristics were associated with reduced [health-related quality of life], and the importance of integrating patients reported outcomes into clinical practice and research.”