A commentary on: “A 12-year population-based study of freezing of gait in Parkinson's disease”

Citation: Crouse JJ and Moustafa AA (2015) A commentary on: " A 12-year population-based study of freezing of gait in Parkinson's disease ". A recent study by Forsaa et al. (2015) details the prospective assessments of a population-based Parkinson's disease (PD) cohort, investigating the long-term progression and associated risk factors of freezing of gait (FOG). Building on previous work examining the progression of psychosis in PD (Forsaa et al., 2010), the authors followed a cohort of 232 PD patients, assessing both motor and non-motor disease features including FOG, severity of parkinsonism, motor complications, psychotic symptoms, and cognitive impairment at 4 and 8 years, and annually thereafter. In this study, Forsaa et al. (2015) utilized a prospective longitudinal research design, allowing for investigating and predicting symptom progression. This predictive capability is of importance to intervention and therapy, as FOG is associated with reduced quality of life (Moore et al., 2007; Walton et al., 2015), increased risk of falls and subsequent medical complications (Bloem et al., 2004), caregiver-burden (Schrag et al., 2006), and self-initiated social isolation (Bloem et al., 2004). Forsaa et al. (2015) suggest that many PD patients may develop FOG during their disease course. This finding aids in remediating a discrepancy in the " freezing " literature, in relation to the highly variable prevalence rates of FOG in PD patients, with past research reporting variable report a FOG point prevalence rate of 25% at the commencement of the study, 75% at the 8-year follow-up, and 63% at the end of the study. This variability in the literature may result from previous overreliance on cross-sectional research, as well as dropout rates stemming from non-PD related comorbidities and increased mortality in PD patients displaying FOG. As shown by Forsaa et al's (2015) long-term prospective follow-up design, repeated assessments of disease features and the use of robust statistical analyses, including logistic regression models and generalized estimating equations, the risk factors and concomitant features of FOG were explored in isolation from one another. The analyses revealed a significant relationship between motor fluctuations and FOG, as non-" freezers " presenting with motor fluctuations at the commencement of the study had more than three times the likelihood of developing FOG during the 12-year follow-up period, as compared with patients without motor fluctuations at baseline. Interestingly, dyskinesias were associated with a statistically non-significant (but still greater than 60%) reduced risk of incidence of FOG during follow-up, a …