Comparison of three scales to evaluate personality traits in Parkinson's disease: which one to use?

BACKGROUND: Personality traits have gained interest in the field of disability and stress, because they may either prompt or deny compliance. They can also foster motivation and influence outcome. Parkinson disease (PD) is a disabling and stressful condition that requires coping strategies and rehabilitation plans. Three constructs and their relative scales have been a matter of investigation, namely Dispositional Optimism (DO), Locus-of-Control (LOC), and Sense-of- Coherence (SOC).

AIM: The present study compared the psychometric properties of three constructs in Parkinson's Disease (PD). The health-related variables were: Emotional Distress (ED), Quality of Life (HR- QoL) and Activities of Daily Living (ADL). The final objective was to provide guidance on scale selection to be implemented in clinical protocols.

DESIGN: A cross sectional study.

SETTING AND POPULATION: Participants with PD (n =84) from community-based general physicians.

METHODS: PD patients completed 3 self-report scales, namely Life Orientation Test -Revised (LOT-R, measuring Dispositional Optimism), Internal and External Locus Of Control (LOC-int. LOC-ext) and Sense of Coherence (SOC). All participants had Magnetic Resonance Imaging. The MDS-UPDRS and the Barthel scale were compiled by the investigator with the assistance of a caregiver.

RESULTS: LOC-ext was the only scale to be associated with PD severity and disability (P<0.05). A higher level of LOC-ext was also associated with a higher level of ED (p<0.005). LOT-R was inversely associated with ED. Subjects in the highest tertile had a 41% lower ED (p<0.001). SOC was also inversely associated with degree of ED. Subjects in the highest tertile have a 44% lower ED (P<0.01). Moreover, HR-QoL is associated with several parameters, but LOT-R is the one with the strongest association (P<0.001).

CONCLUSIONS: DO and SOC are predictive of important end-points, namely HR-QoL and ED. DO is even better under this respect. Conversely, those clinicians who are more interested in motor problems may find LOC more suitable. DO may be the most efficient construct to use in PD because of its favorable psychometric properties.

CLINICAL REHABILITATION IMPACT: DO, LOC and SOC are constructs to be implemented in both research and clinical PD protocols. It is recommended to implement these, because they have predictive value especially when HR-QoL and ED are studied.