Phenotypic differences of amyotrophic lateral sclerosis (ALS) in China and Germany

Objective: The aim of this study is to explore phenotypical differences of amyotrophic lateral sclerosis (ALS) between two cohorts from Germany and China. Methods: Registry-based studies of ALS were conducted in South-West Germany from 2010 to 2014 and an ALS clinic in Beijing from 2013 to 2016, respectively. Demographic and clinical features of 663 German and 276 Chinese ALS patients were collected and compared. Results: Mean age-at-onset was higher in German than in Chinese ALS patients [66.6 years (95% CI 65.7, 67.5) vs. 53.2 years (95% CI 52.0, 54.5)]. Age distribution of ALS patients peaked around 70–74 years in Germany and 50–54 years in China. Bulbar onset was more prevalent among German than among Chinese patients (35.9 vs. 22.8%). Diagnostic delay was higher in the Chinese than in the German study sample (12 vs. 5 months). Cognitive deficits were more pronounced in the Chinese cohort. Both cohorts differed in smoking habits, prevalence of diabetes and in body mass index (BMI). Conclusions: The apparent discrepancies between German and Chinese ALS patients (age at onset, gender distribution, bulbar forms, cognitive dysfunction, risk factors) reveal a quite different clinical phenotype in China, maybe due to socioeconomic status, environmental factors or genetic background. The observed differences in phenotype need to be pursued by further epidemiological studies on environmental and genetic risk factors.