A functional polymorphism in the promoter region of MAOA gene is associated with daytime sleepiness in healthy subjects

Excessive daytime sleepiness (EDS) is one of the main causes of car and industrial accidents and it is associated with increased morbidity and alterations in quality of life. Prevalence of EDS in the general population around the world ranges from 6.2 to 32.4%, with a heritability of 38-40%. However, few studies have explored the role of candidate genes in EDS. Monoamine oxidase A (MAOA) gene has an important role in the regulation of neurotransmitter levels and a large number of human behaviors. We hypothesized that a functional VNTR in the promoter region of the MAOA gene might be associated with daytime sleepiness in healthy individuals. The Epworth sleepiness scale (ESS) was applied to 210 Colombian healthy subjects (university students), which were genotyped for MAOA-uVNTR. MAOA-uVNTR showed a significant association with ESS scores (p = 0.01): 3/3 genotype carriers had the lowest scores. These results were supported by differences in MAOA-uVNTR frequencies between diurnal somnolence categories (p = 0.03). Our finding provides evidence for the first time that MAOA-uVNTR has a significant association with EDS in healthy subjects. Finally, these data suggest that functional variations in MAOA gene could have a role in other phenotypes of neuropsychiatric relevance.