More than half of middle-aged women who still have regular menstrual cycles have hot flashes, a new study has found. 

But there are marked statistical differences by ethnic groups, according to the report in the online edition of Menopause, the journal of the North American Menopause Society.

The survey was conducted by researchers at Group Health and Fred Hutchinson Cancer Research Center in Seattle, Wash., on a diverse group of 1,500 women, including Hawaiian/Pacific Islanders, Vietnamese, Filipinos, Japanese, East Indians, Chinese, blacks and whites, 45 to 56 years old, with regular cycles and no skipped periods. They were not taking hormones.

The groups with the highest proportions reporting hot flashes or night sweats were Native American (67 percent) and black (61 percent) women. Next came whites at 58 percent and Hawaiians/Pacific islanders at 45.5 percent. 

Asian and Hispanic women were much less likely to have these symptoms. Of Asian women, only 31 percent of Filipino, 26 percent of Japanese, 25 percent of East Indian, 23 percent of other Asian and 18 percent of Chinese women had the symptoms.

White women who had symptoms were more likely to eat soy, the study found. There was no relationship with soy in the other ethnic groups.

The study was funded by Otsuka Pharmaceutical Co. Ltd., which is developing S-Equol, a compound that may mimic estrogen and could be a potential treatment for menopausal symptoms.