A US study has revived the argument about what is the best age for women to start having regular mammograms.

When a woman turns 40 is the optimal age to start having regular mammograms to reduce the number of breast cancer deaths, the findings of a US study suggests.

Researchers in New York compared the commonly recommended mammograms schemes used in the US to estimate the most effective at reducing breast cancer mortality.

These included annual screening from age 40; annual screening between the ages of 45 to 54 then every second year from 55 to 79; or every second year from 50 to 74.

According to the computer modelling, the first scheme reduced breast cancer deaths by an estimated 40 per cent, compared to 23 per cent and 31 per cent for the other schemes.

"If the goal is to avert the most breast cancer deaths and gain the most life-years, CISNET modelling shows that the optimal age of initiation for screening mammography is 40 years, the optimal screening is annual, and the optimal stopping age is when a woman's life expectancy is less than five to seven years," the authors concluded.

The findings are published in the international journal Cancer.

In Australia, the national breast cancer screening program - BreastScreen Australia - invites women aged between 50 and 74 for a free mammogram every two years.

When to initiate screening for breast cancer has sparked controversy in the past, says Cancer Council Australia boss Professor Sanchia Aranda.

"There was a lot of controversy at the time when the federal government extended the breast program here from 69 to 74 in terms of whether that age group should benefit from extra screening as opposed to going down to those in their 40s," said Professor Sanchia Aranda.

"We currently probably over-screen some women at two years (intervals) and under-screen others," Prof Aranda added.

Despite this, women at average risk of breast cancer should be "confident" in the national screening program, says Prof Aranda.

However, women with a strong family history of breast cancer are advised to be more vigilant and should seek advice from their GP

"If you have got a strong family history of beast cancer you probably want to be more vigilant than the current screening program might give you and particularly if you are young," said Prof Aranda.

Professor Aranda says what the US study importantly confirms is that mammograms do save lives.

Breast cancer deaths have reduced by nearly 50 per cent since the introduction of mammography in Australia and more women should participate in the nations screening program.

"We currently have a less than 70 per cent participation, so we would like to see all women in the screening age participate and that would help to reduce breast cancer mortality even further," said Professor Aranda.