A large study of sleep EEG (n=800) found a significant association between a single nucleotide polymorphism in the adenosine deaminase gene (ADA G22A) and sleep EEG characteristics, with carriers of the A allele showing higher power in delta and theta bands relative to non-carriers, suggesting higher sleep efficiency in A allele carriers (Mazzotti et al., 2012). Adenosin plays a role in sleep homeostasis, and A allele has been associated with decreased ADA activity and lower adenosine clearance (Battistuzzi et al., 1981), resulting in higher sleep efficiency.
