Comparable progression of spinocerebellar ataxias between Caucasians and Chinese

Introduction: The aim of this study is to reappraise the progression of the five most common spinocerebellar ataxias (SCAs) in the Chinese population and to establish a much-needed critical comparison with that in other ethnic groups. There are very few longitudinal cohort studies of SCAs in Asian populations. An intriguing finding in an earlier study demonstrated a faster progression of SCA among Chinese than that among Caucasians. Methods: Patients with SCA1, SCA2, SCA3, SCA6 or SCA17 were consecutively assessed using the scale for the assessment and rating of ataxia (SARA) for five years. A linear mixed model was used to compare the annual progression rates measured using the SARA among patients with different SCA subtypes. Predictors of the progression rates were analyzed. Results: A total of 199 patients with SCA (10 with SCA1, 37 with SCA2, 118 with SCA3, 25 with SCA6 and 9 with SCA17) were enrolled. The mean annual increase in SARA scores was 1.23 points for SCA1, 1.52 points for SCA2, 1.60 points for SCA3, 0.99 points for SCA6 and 3.26 points for SCA17. A larger CAG repeat length (≥74) was associated with faster progression in SCA3, whereas a lower total SARA score at the first visit (<12) was associated with faster clinical progression in SCA6. Conclusion: The results of this study confirm that the annual progression rates of SCA2 and SCA3 are comparable between Han Chinese and other ethnic populations. More studies are warranted to confirm the rapid progression of SCA17 observed in our cohort.