Ethnicity and Parkinson's Disease: Motor and Nonmotor Features and Disease Progression in Latino Patients Living in Rural California

Abstract

Background: Parkinson's disease (PD) is the second most common neurodegenerative disorder among older adults worldwide. Currently, studies of PD progression rely primarily on White non-Latino (WNL) patients. Here, we compare clinical profiles and PD progression in Latino and WNL patients enrolled in a community-based study in rural Central California.

Method: PD patients within 5 years of diagnosis were identified from 3 counties between 2001 and 2015. During up to 3 visits, participants were examined by movement disorders specialists and interviewed. We analyzed cross-sectional differences in PD clinical features severity at each study visit and used linear mixed models and Cox proportional hazards models to compare motor, nonmotor, and disability progression longitudinally and to assess time to death in Latinos compared to WNL patients.

Results: Of 775 patients included, 138 (18%) self-identified as Latino and presented with earlier age at diagnosis (63.6 vs 68.9) and death (78.6 vs 81.5) than WNL. Motor (hazard ratio [HR] = 1.17 [0.71, 1.94]) and nonmotor symptoms did not progress faster in Latino versus WNL patients after accounting for differences in baseline symptom severity. However, Latino patients progressed to disability stages according to Hoehn and Yahr faster than WNL (HR = 1.81 [1.11, 2.96]). Motor and nonmotor symptoms in Latino patients were also medically managed less well than in WNL.

Conclusions: Our PD study with a large proportion of Latino enrollees and progression data reveals disparities in clinical features and progression by ethnicity that may reflect healthcare access and structural socioeconomic disadvantages in Latino patients with PD.

Keywords: Cohort study; Disease progression; Ethnic differences; Minority aging; Motor decline.

Figure 1.

Linear mixed models predictions for total LED means, by ethnicity, using 4 different progression measures (PD duration, age, UPDRSm, and H&Y). Total N in models = 773. Panel A model adjusted for sex and age. Panel B adjusted for sex and PD duration. Panels C and D models adjusted for sex, PD duration, and age. Model estimates are shown in Supplementary Table 4. H&Y= Hoehn and Yahr stage; LED = levodopa equivalent dose; PD = Parkinson’s disease; UPDRSm = Unified Parkinson’s Disease Rating Scale motor exam scores; WNL = White non-Latino.

Figure 2.

Time to motor progression event models comparing Latino to White non-Latino patients during PEG study follow-up. Model 1 adjusted for age at PD diagnosis, PD duration, sex, PEG Wave 1/2, and smoking. Model 2: adjusted for Model 1 variables + baseline UPDRSm or H&Y. H&Y = Hoehn and Yahr stage; HR = hazard ratio; PD = Parkinson’s disease; PEG = Parkinson’s Environment and Genes Study; UPDRSm = Unified Parkinson’s Disease Rating Scale motor exam scores; WNL = White non-Latino; N (%) events and total N in models = UPDRSm 35+: Latino 22 (36.7)/WNL 95 (27.5)/total N = 405 H&Y 3+: Latino 26 (39.4)/ WNL 81 (25.7)/total N=380

Figure 3.

Observed and predicted UPDRSm and H&Y means for Latino and WNL groups using 2 time scales (by study visit and by years from baseline) during PEG Study follow-up (total N = 770). Observed are the actual means for each group, Latino and WNL, at each time point (study visit or year). Predicted mean estimates obtained from linear mixed models adjusted for sex, PD duration, age, smoking, PEG Wave 1 or 2. Model estimates are shown in Supplementary Table 5. H&Y = Hoehn and Yahr stage; PD = Parkinson’s disease; PEG = Parkinson’s Environment and Genes Study; UPDRSm = Unified Parkinson’s Disease Rating Scale motor exam scores; WNL = White non-Latino.