NOS3 and Alzheimer disease: The results from the meta-analysis showed that there was a significant association between the polymorphism of NOS3 and risk of AD (overdominant model: P < 0.001, OR = 1.18, 95%CI = 1.08–1.29), which contrasts with the results from previous meta-analyses38, 39 that observed a null association between the G894T polymorphism and AD risk.