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Drinking and breast cancer linked - but is it the smoke, or the drink?
Every drink a woman takes increases her chances of developing breast cancer. But researchers have cleared away the confusion over whether it's the cigarette she smokes along with the drink that leads to the cancer.
Now scientists are sure that it is the alcohol that matters, according to a report in the Nov. 18 British Journal of Cancer (Vol. 87: 1234-1245).
The number of women developing breast cancer is increasing each year, according to the American Cancer Society (news - web sites). This year, more than 203,000 women will be diagnosed with the disease. Last year it was 192,000 women.
Part of the increase is due to the aging of the population; breast cancer rates increase with age. But there is also a real increase in the rate of breast cancer for all women.
There are many risk factors other than age. Hormone replacement therapy and obesity are two risk factors that women can control. Another is alcohol consumption. For several years, it has been thought that drinking increases a woman's risk of breast cancer.
But past studies haven't been consistent. Also, because smoking often accompanies drinking, researcher haven't been sure that alcohol was the most important factor.
The study, led by researchers from Cancer Research UK, in Oxford, UK, included dozens of the most prestigious researchers from around the world to look into the causes of cancer. Their report reviewed the results of 65 separate studies, involving nearly 200,000 women.
They looked at two issues. The first was how much a woman needed to drink to increase her chance of breast cancer. The second was whether smoking increased this risk.
They found that a single daily drink of 1 oz of spirits such as whiskey, gin, or vodka, or 3 oz of wine increases a woman's breast cancer risk slightly — perhaps 3% to 4%. But after that, every additional daily drink increases the risk by 7%. By four drinks a day, a woman's risk goes to 30%.
Smoking didn't make the risk worse, the authors said. This means that for women who drink alcohol, their intake is the major risk factor. Smoking had no extra effect.
The researchers did not feel that the studies they examined could link breast cancer to smoking. And, a recent report in the medical journal The Lancet found that tobacco as a risk factor for breast cancer was best tied to teenage smoking. The current study did not look at the age of the smokers.
The researchers did look at a woman's lifetime risk of breast cancer by age 80, depending on how much they drink. A non-drinker's chances were one in 11. But, a heavy drinker had about a one in seven chance of developing breast cancer by age 80.
The effect of alcohol was there regardless of a woman's race, education, family history, use of hormone replacement therapy, or other risk factors. No matter what a woman's baseline risk, it went up 7% with each drink.
So is drinking a health hazard? Not necessarily if it is taken in moderation, the researchers said.
They cautioned that although daily drinking will increase a woman's breast cancer risk, she needs to keep in mind its beneficial effect, in moderation, on heart disease.