Perceived consequences and catastrophising help explain health-related quality of life in Parkinson's disease. A cross-sectional study

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Introduction Motor complications are major determinants of disability in Parkinson's disease (PD), yet clinician-rated motor complication severity does not fully explain variability in health-related quality of life (HRQoL). This study examined the contribution of illness perceptions and cognitive-behavioural responses to HRQoL alongside motor complication severity in people with PD. Methods This multi-centre, cross-sectional study recruited 58 people with idiopathic PD (median age 68 years; 55.2% male; 48.3% from minoritised ethnic backgrounds; Hoehn & Yahr stage 2-3). All underwent assessment of motor complications (Movement Disorder Society-Unified Parkinson's Disease Rating Scale; MDS-UPDRS Part IV) and HRQoL (Parkinson's Disease Questionnaire-39 Summary Index; PDQ-39 SI). Illness perceptions were measured with Illness Perception Questionnaire-Revised (IPQ-R) Part 2, and cognitive-behavioural responses with Cognitive and Behavioural Responses Questionnaire (CBRQ). Regression models were adjusted for age, sex, disease duration, motor severity (MDS-UPDRS Part III), levodopa equivalent daily dose (LEDD), anxiety, depression, and cognitive function. A subset (n=47) completed 7-day Parkinson's KinetiGraph monitoring. Results Demographic and clinical covariates explained 77.3% of variance in HRQoL (R 2 =0.773). Adding motor complication severity explained a significant additional 3.7% (ΔR 2 =0.037, P=0.004). Subsequent inclusion of illness consequences (IPQ-R) and catastrophising (CBRQ) explained a further 4.1% (ΔR 2 =0.041, P=0.004), yielding a final adjusted R 2 of 0.815. In the fully adjusted model, catastrophising (B=0.797, P=0.027) and perceived consequences (B=0.767, P=0.013) remained independently associated with HRQoL. Conclusion HRQoL in PD appears to depend not only on motor complication severity, but also on patients' interpretations and responses. Clinicians should assess both to guide holistic care and support adaptive coping.