Aging is the most important risk factor for PD, and may increase the likelihood of invasion of harmful antigens in the GI tract.216 Age-related GI changes such as slowed gastric emptying, decreased GI tract motility, reductions in protective GI mucous, reductions in luminal digestive enzymes would increase the time of exposure to dietary α-synuclein.216 The intestinal epithelial barrier may also become progressively more permeable with age.217. The gene discussed is SNCA; the disease is Parkinson disease.