Predictors of clinically meaningful change in PDQ-39 in Parkinson's disease.

OBJECTIVE

To determine predictors of clinically meaningful change in Health-Related Quality of Life (HRQL) in patients with Parkinson's disease (PD).

BACKGROUND

There is limited literature on longitudinal predictors of change in HRQL in PD.

METHODS

Data were collected from the National Parkinson Foundation Quality Improvement Initiative (NPF-QII) registry, a multicenter, longitudinal observational study. HRQL is measured by the Parkinson's Disease Questionnaire-39 (PDQ-39). We calculated the PDQ-39 change between every two consecutive visits and generated binary outcomes using the threshold for clinically meaningful change (previously determined to be 1.6). We used chi-squared tests for discrete and t-test for continuous variables for baseline characteristic comparison between patient groups of interest. Generalized linear mixed models with repeated measures were used for identifying the predictors of whether PDQ-39 outcomes worsen over time.

RESULTS

Of 8041 subjects enrolled, 5250 had at least one follow-up visit and were included in the analysis. Subjects were separated into two groups, "worse" and "not worse" based on PDQ-39 change >1.6 across consecutive visits. The "worse" group was more likely to be older (p = 0.001), to have motor fluctuations (p = 0.011), be on cognitive enhancers (p = 0.01), and to have more impaired immediate five-word recall (p = 0.04). The "non-worse" group was more likely to have rest tremor (p = 0.003), and to utilize social work/counseling (p = 0.046).

CONCLUSIONS

The majority of predictors of worsening of HRQL are baseline disease and demographic characteristics that are difficult to modify. The positive effect of social service/counseling is intriguing and important to further explore in controlled interventional studies.