Results indicate that 19.5 percent of US adults reported having moderate to excessive sleepiness, which was comparable between men and women. Furthermore, 11 percent of participants reported severe sleepiness, which was more prevalent in women (13 percent) than in men (8.6 percent). The cross-sectional study involved a representative sample of 8,937 adults. In a previous study the author reported that the prevalence of excessive daytime sleepiness in five European countries was 15 percent.