However, a clear association of TNFA -850*2 with AD has only previously been reported as a synergistic effect in combination with APOE ε4 in a Northern Irish population [11], while a similar study in a population from Northern Spain failed to produce evidence in support of a synergistic effect between TNFA -850*2 and APOE ε4 [12]. Here, TNF is linked to Alzheimer disease.