Lifestyle-Related Risk Factors
Women who do not have children or who had their first child after age 30 have a slightly higher breast cancer risk. Women who became pregnant at an early age or have many children are at a reduced risk for breast cancer. Because pregnancy reduces a woman’s menstrual cycles over her lifetime it is thought to be the reason for the reduced risk.
Oral Contraceptive Use
Studies show that women using oral contraceptives (birth control pills) have a slightly greater risk of breast cancer than women who have never used them. Once the pills are stopped the risk will return to normal over time. If the pills were stopped over ten years ago then there does not appear to be an increased risk. If you use oral contraceptives or are considering using them you should discuss the risks and benefits with your physician.
Hormone Therapy After Menopause
Hormone replacement therapy has been used for many years to relieve symptoms of menopause and help prevent osteoporosis. Estrogen and sometimes progesterone are prescribed. Early studies suggested these hormones might have other health benefits as well, but those benefits have not been found in more recent, better designed studies.
Women who still have a uterus are generally given estrogen and progesterone; this is called combined hormone therapy. Progesterone is used because using estrogen alone increases the risk of uterine cancer. Women who have had a hysterectomy and no longer have a uterus can take estrogen alone.
Combined Hormone Therapy
Large studies have shown that the use of combined post-menopausal hormone therapy increases the risk of getting breast cancer and the likelihood that it may be found at a more advanced stage. The increased risk from combined HT appears to apply only to current and recent users. Within five years of stopping hormone therapy a woman’s risk appears to return to that of the general population.
Bioidentical hormones have been marketed as a safe alternative to estrogen and progesterone. There are very few studies comparing bioidentical hormones to synthetic hormones and no evidence to support that are safer to use. Until studies prove otherwise, the use of these hormones should be assumed to carry the same health risks as any other type of hormone therapy.
The use of estrogen therapy does not appear to increase the risk of developing breast cancer. Some studies have found that long term use of estrogen alone (ten years or longer) increases the risk of breast and ovarian cancer.
Other than the short-term relief of menopausal symptoms, there appears to be little support for the use of either Combined Hormone Therapy or Estrogen Therapy. Aside from the increased risk of breast cancer, combined HT also appears to increase the risk of heart disease, blood clots, and strokes. On the other hand, it does lower the risk of colorectal cancer and osteoporosis. We do have ways to prevent and treat osteoporosis and regular colonoscopy screening is the best defense against colorectal cancer. And although estrogen therapy does not seem to increase breast cancer risk, it does increase the risk of stroke.
A decision to use hormone therapy should be made by a woman and her physician after discussing the severity of symptoms from menopause and the possible risks and benefits of therapy. Her other risk factors for heart disease, breast cancer, and osteoporosis should be considered as well. If a decision is made to try hormone therapy for symptoms of menopause, it is usually best to use it at the lowest dose that works for her and for as short a time as possible.
There are some studies that suggest breast-feeding may slightly lower breast cancer risk, especially if it is continued for 1½ to 2 years. This has been a difficult area to study, especially in countries such as the United States, where breast-feeding for this long is uncommon.
The explanation for this possible effect may be that breast-feeding reduces a woman's total number of lifetime menstrual cycles.
Alcohol consumption is clearly linked to an increased risk of developing breast cancer and the risk increases with the amount of alcohol consumed. When compared to non-drinkers, women who consume one alcoholic beverage a day have a very small increase in risk. Women who have two to five drinks daily increase their risk about 1½ times of women who drink no alcohol. Excessive alcohol use is also known to increase the risk of developing many other cancers including: mouth, throat, esophageal and liver. Recommendations are that women have no more than one alcoholic beverage a day.
Being overweight or obese has been found to increase breast cancer risk, especially for post- menopausal women. Before menopause your ovaries produce most of your estrogen, and fat tissue produces a small amount of estrogen. When the ovaries stop producing estrogen (after menopause), most of a woman's estrogen comes from fat tissue. By having more fat tissue after menopause, your chance of getting breast cancer may be increased due to of raised estrogen levels. Women who are overweight also tend to have higher blood insulin levels which have been linked to some cancers, including breast cancer.
The connection between weight and breast cancer risk is complex. Risk appears to be increased for women who gained weight as an adult but may not be increased among those who have been overweight since childhood. Excess fat in the waist area may affect risk more than the same amount of fat in the hips and thighs. Researchers believe that fat cells in various parts of the body have subtle differences that may explain this.
It is important maintain a healthy weight throughout your life by balancing your food intake with physical activity and avoiding excessive weight gain.
There is growing evidence that physical activity in the form of exercise reduces breast cancer risk. The debate is how much exercise is needed. A study from the Women's Health Initiative recommends as little as 1¼ to 2½ hours per week of brisk walking can reduce a woman's risk by 18 percent. Walking ten hours a week further reduced the risk. Current recommendations support 30 to 60 minutes of physical activity at least five days a week.