Women have different warning signs for a heart attack than men, with unusual fatigue and sleeplessness topping the list of symptoms.

A study in Monday's issue of the American Heart Association journal Circulation surveyed 515 women who have had heart attacks.

The survey found that 95 per cent of the women had fatigue or sleeplessness up to a month before their attacks.

The most commonly known early indicator of a heart attack is chest pain, but the study found that 43 per cent of the women never had any pain in the chest, said researcher Jean C. McSweeney, a professor at the University of Arkansas College of Nursing.

The scientists said this is the first time fatigue and sleeplessness have been identified as early warnings of a heart attack.

They said they don't know whether these findings apply to men.

The study surveyed women aged 29 to 97 who had been hospitalized after suffering a heart attack.

They were shown a list of 70 symptoms and asked to rate them based on how frequently and severely they experienced those symptoms in the months leading up their heart attacks.

McSweeney said the fatigue the women experienced was typically so severe that it interfered with their normal activities.

She said that even though women fear breast cancer more, heart disease is the number one killer of women.