After the age of 30 a lack of exercise has a larger impact on women's heart health than any other known risk factor, including being overweight.

In Australia the four largest risk factors for heart disease is "excess weight (high BMI); smoking; high blood pressure; and physical inactivity," a BMJ-British Medical Journal news release reported. These risk factors are linked to over half of global heart disease.

To make their findings the researchers looked at population attributable risk (PAR), which is a mathematical formula that determines how many fewer cases of an illness would exist if a specific risk factor was eliminated.

For the formula the team used data from 32,154 patients who participated in the Australian Longitudinal Study on Women's Health.

The prevalence of smoking fell from 28 percent in the early 20s to five percent in the early 70s of the women's lifespan. In contrast rates of inactivity tended to slowly decrease over the years.

Using the formula the team found that before age 30 smoking was the primary cause of heart disease; after age 30 through the 80s inactivity was the leading cause of heart disease.

The research suggests if every woman between the ages of 30 and 90 got the recommended amount of exercise than 2,000 middle-aged women's lives would be saved every year in Australia.

The researchers suggest efforts continue to get young people to stop smoking, but promoting physical activity in women of this age group should be of higher priority than it has been in the past. The researchers believe the focus has been placed to largely on obesity.

"Our data suggest that national [programs] for the promotion and maintenance of physical activity, across the adult lifespan, but especially in young adulthood, deserve to be a much higher public health priority for women than they are now," the researchers said in the news release.