Val66Met polymorphism of brain-derived neurotrophic factor is associated with idiopathic dystonia.

The Val66Met (G196A; rs6265) single nucleotide polymorphism of brain-derived neurotrophic factor (BDNF) affects morphology and neuronal activity, and is expected to be associated with central nervous system disorders. However, it remains controversial whether Val66Met polymorphism is a risk factor for idiopathic dystonia. We aimed to clarify the impact of BDNF polymorphism on idiopathic dystonia. A literature search of PubMed was carried out. A random-effects model was employed for the meta-analysis. A pooled odds ratio (OR) was calculated along with 95% confidence intervals (CI) to reflect the risk of idiopathic dystonia in each genotype (GG, AG, AA) or minor allele. The proportion of variation due to heterogeneity was computed and expressed as I(2). Five case-control studies, comprising a total sample size of 1804 subjects (784 idiopathic dystonia patients, 1020 normal controls), were included in this meta-analysis. AA genotype was significantly more frequent in patients with idiopathic dystonia (OR=1.47, 95% CI 1.09-1.99, p=0.01, four studies, n=1716). This finding was derived from homogeneous studies (p=0.97, I(2)=0%). Our meta-analysis has revealed a significant overall effect of the AA genotype on the development of idiopathic dystonia.