But, as normal serum IL-6 levels were found in the early stages of late-onset sporadic AD (van Duijn et al. 1990;) and as IL-6 secretion is found to be decreased in severely demented patients versus controls (suggesting that it might negatively correlate with the severity of dementia; Kalman et al. 1997; Sala et al. 2003), the AD subtype and the stage of disease might explain the discrepancies observed between studies. This evidence concerns the gene IL6 and Alzheimer disease.