In a longer study (52 weeks) on AD patients, a higher dose of resveratrol (up to 2 g/day) decreased the level of metalloproteinase MMP9, which is involved in maintaining the integrity of the BBB, in the cerebrospinal fluid, and slowed down progressive cognitive decline [149], strongly supporting the role of resveratrol as a neuroprotective agent also in AD patients. This evidence concerns the gene MMP9 and Alzheimer disease.