Knowing risk factors can help you reduce the chance of getting this disease, says Charmaine Gauci, director, Health Promotion and Disease Prevention Directorate.

A risk factor is anything that affects a person’s chance of getting a disease, such as cancer. However, having a risk factor or a number of risk factors does not mean that you will get the disease.

Most women who have one or more breast cancer risk factors never develop the disease, while many women with breast cancer have no apparent risk factors.

Knowing what the risk factors are is a guide to help lead a lifestyle that reduces them as this will decrease the chance of getting cancer.

We cannot change some risk factors, like age, but we can change others.

Having children

Women who have not had children or who had their first child after age 30 have a slightly higher breast cancer risk. Having many pregnancies and becoming pregnant at an early age reduces breast cancer risk.

Birth control

Oral contraceptives: a number of studies have shown women using oral contra-ceptives have a slightly increased risk of breast cancer than women who have never used them. This risk seems to go back to normal 10 years after stopping them.

Depot-medroxyprogesterone acetate (DMPA; Depo-Provera) is an injectable form of progesterone that is given once every three months as birth control.

A few studies have looked at the effect of DMPA on breast cancer risk. Women currently using DMPA seem to have an increase in risk, but that does not seem to be increased if this drug was used more than five years ago.

Most women who have one or more breast cancer risk factors never develop the disease, while many women with breast cancer have no apparent risk factors

Hormone therapy after menopause

Hormone therapy using oestrogen (often combined with progesterone) has been used for many years to help relieve symptoms of menopause and to help prevent osteoporosis.

Combined hormone therapy: the use of combined post-menopausal hormone therapy increases the risk of getting breast cancer. It may also increase the chances of dying from breast cancer. The increased risk appears to apply only to current and recent users. A woman’s breast cancer risk seems to return to that of the general population within five years of stopping treatment.

Oestrogen therapy: the use of oestrogen alone after menopause does not appear to increase the risk of developing breast cancer significantly, if at all. But when used long term (for more than 10 years), such therapy has been found to increase the risk of ovarian and breast cancer in some studies.

The decision to use hormone therapy should be made by a woman and her doctor after weighing the possible risks and benefits (including the severity of her menopausal symptoms), and considering her other risk factors for heart disease, breast cancer and osteoporosis.

Breastfeeding

Some studies suggest that breastfeeding may slightly lower breast cancer risk, especially if it is continued for 18 months to two years. This can be explained by the possible effect of reducing a woman’s total number of lifetime menstrual cycles.

Drinking alcohol

Consumption of alcohol is clearly linked to an increased risk of developing breast cancer. The risk increases with the amount of alcohol consumed.

Compared with non-drinkers, women who consume one alcoholic drink a day have a very small increase in risk. Those who have two to five drinks daily have about 1.5 times the risk of women who do not drink. It is recommended women have no more than one alcoholic drink a day.

Being overweight or obese

Being overweight or obese after menopause increases breast cancer risk.

Before menopause, the ovaries produce most of the body’s oestrogen, and fat tissue produces a small amount of oestrogen.

After menopause (when the ovaries stop making oestrogen), most of a woman’s oestrogen comes from fat tissue.

Having more fat tissue after menopause can increase the chance of getting breast cancer by raising oestrogen levels. Also, women who are overweight tend to have higher blood insulin levels, which have also been linked to some cancers, including breast cancer.

It is important to maintain a healthy weight throughout life by balancing food intake with physical activity and avoiding excessive weight gain.

Physical activity

Evidence is growing that physical activity in the form of exercise reduces breast cancer risk. The main question is how much exercise is needed.

Various studies suggest that longer duration provides most benefit, and that such activity need not be strenuous.

There are a number of factors whose effect on breast cancer is not clear from the various studies conducted.

Diet

Many studies have looked for a link between certain diets and breast cancer risk, but so far, the results have been conflicting.

Some studies indicated diet may play a role, while others found no evidence it does.

Studies have looked at the amount of fat in the diet, intake of fruits and vegetables, and intake of meat. No clear link to breast cancer risk was found.

Most studies have found that breast cancer is less common in countries where the typical diet is low in total fat, low in polyunsaturated fat and low in saturated fat.

However, this may be partly due to the effect of diet on body weight.

Chemicals in the environment

A great deal of research has been reported and more is being done to understand possible environmental influences on breast cancer risk. Compounds in the environment that have oestrogen-like properties are of special interest.

For example, substances found in some plastics, certain cosmetics and personal care products, pesticides and PCBs (polychlorinated biphenyls) seem to have such properties.

These could, in theory, affect breast cancer risk. However, current research does not show a clear link between breast cancer risk and exposure.

Tobacco smoke

In recent years, studies have found that long-term heavy smoking is linked to a higher risk of breast cancer.

Some studies have found that the risk is highest in certain groups, such as women who started smoking when young.

Evidence about second-hand smoke and breast cancer risk in human studies is controversial, so this possible link is yet another reason to avoid it.

Night work

Several studies have suggested that women who work at night, such as nurses on a night shift, may have an increased risk of developing breast cancer.

This is a fairly recent finding, and more studies are looking at this issue.

Some researchers think the effect may be due to changes in levels of melatonin, a hormone whose production is affected by the body’s exposure to light, but other hormones are also being studied.

For more advice on how to adopt a healthy lifestyle, contact the Health Promotion and Disease Prevention Directorate on 2326 6000.