Australia's 45 and Up Study has found a significant association between breastfeeding and incidence of cardiovascular disease.

Breastfeeding significantly reduces a woman's risk of dying from cardiovascular disease, Australia's largest cohort study has found.

Research from the Sax Institute's 45 and Up Study, which was presented at a forum in Sydney on Tuesday, found breastfeeding reduced a woman's risk of developing cardiovascular disease (CVD) by 14 per cent.

"The risk of dying from cardiovascular disease was about 34 per cent lower," lead researcher Ms Binh Nguyen told AAP.

"This is very meaningful because cardiovascular disease is the biggest killer of women worldwide and in Australia."

Researchers, led by the PhD student at Sydney University's school of public health, followed a sample of 1000 mothers for six years to investigate the association between breastfeeding and the risk of developing CVD.

Not only did they find an association between breastfeeding and a lower risk of CVD but the longer a woman breastfed the lower their risk, Ms Nguyen said.

According to the data, a woman who breastfed for between 12 to 24 months had a 16 per cent lower risk of developing CVD.

Ms Nguyen said the findings were consistent with previous studies that suggested breastfeeding was not only good for the baby but for the mother's heart too.

"We usually look at lifestyle risk factors like physical activity or diet but other behaviours that can be modified like breastfeeding ... are worthwhile to consider as well," she said.

The 45 and Up study follows the health of more than a quarter of a million NSW men and women, who have filled in a comprehensive questionnaire about their health.

So far it has led to more than 240 research findings on a wide range of issues from cancer to the use of prescription medicine.

This knowledge has been used by more than 25 public health policies agencies across the country, study scientific director Professor Emily Banks says.

The next phase of the study will involve the collection of up to 50,000 blood samples to provide a "complete picture" of people's health risk and how to stay healthy in the long term.

Samples will be stored in the soon-to-be opened NSW State Biobank.

A pilot study is currently underway to collect the first blood sample from a small number of participants to explore the most convenient approach to larger-scale collection.