Hot flash pajamas aren't glamorous, but they are popular as the ranks of women in their 50s expand. A 2004 study conducted at Wayne State looked at the sleep quality of women ages 46 to 51, who experienced an average of five hot flashes per night. "They awakened first and then they flashed," said Robert R. Freedman, a professor of psychiatry and obstetrics and gynecology, who conducted the study with Timothy A. Roehrs, a sleep researcher. "Perhaps their waking up is what triggered the flash."