Association of Blood Type Categories with Idiopathic Epilepsy: A Population Based Case-Control Study in Iran.

We determined the epidemiological association between idiopathic epilepsy and blood antigen type. We carried-out broad patient-finding exercise in this case control study areas in damavand (Tehran) through various means to identify subjects with idiopathic epilepsy and their matched controls. Each patient was carefully examined by using a detailed case-history. The controls were recruited from the same area and from the same source population at the same time. The blood type was independently determined. The type-I and Type-II errors used were 0.01% and 0.1%, respectively. A total of 52 subjects with idiopathic epilepsy and their matched controls were recruited. Both were statistically comparable. The most frequent overall blood type category was A (n=43, 41.3%), followed by O (n=35, 33.6%), B (n=24, 23.5%) and AB (n=2, 1.9%). McNemar's test retrieved a significant difference in the proportion of O blood type alone (χ²=6.5, OR=1.7, 95% CI 1.2-2.5, p=0.01). Upon fixed-effects conditional logistic regression for O, we estimated an odds of 5.0 (99% CI 1.9-13.1, RR=2.8, p=0.001) for idiopathic epilepsy with a coefficient of determination of 16.4% and effect size of 0.9. Upon bootstrap regression after 100x replication of our sample, the odds ratio was estimated to be 6.5 (99%CI 2.4-17.9), p=0.001. The actual sample power was 98.2%. We found a positive epidemiological association between O blood type and idiopathic epilepsy. Further research may affirm this and, therefore, strengthen our understanding further about idiopathic epilepsy.