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Caffeine and Atrial Fibrillation
You may not realize it, but your heart is an electrical system. Each beat of your heart is started by an electrical pulse of what is called the sinus node, which is in the upper part of the right atrium (the top section of your heart, towards your right side). In normal sinus rhythm, the sinus node sends electrical impulses to the two upper chambers of your heart, the atria, and they then contract, or beat, simultaneously.
Good News for Women Who Drink Coffee
There’s a good bit of medical lore that says that caffeine will increase your blood pressure. It’s true in the sense that there are short-term clinical studies that show that caffeine intake can raise blood levels of stress hormones associated with hypertension, but these studies have all been only up to a week or so in length. Recently a team of researchers at Harvard published the first study of the effects of long-term caffeine intake among women (JAMA. 2005;294:2330-2335 ).
Coffee and Diabetes Risk
Researchers in Iowa recently conducted a study of 28,812 post-menopausal women to assess the impact of coffee drinking on their risk of developing diabetes (Arch Intern Med. 2006;166:1311-1316).
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At some point in their lives, as many as half of all women have what is called benign breast disease. This catch-all term can include such diagnoses as fibrocystic breast disease, mastitis (inflammation of the breast), or simply "lumpy breasts." Having benign breast disease is sometimes linked to an increased risk of breast cancer, but this is only true if a breast biopsy shows the presence of abnormal breast cells.
Many women with fibrocystic breast disease are told to avoid caffeine because this seems to help minimize the symptoms of the disease, which include lumps in the breast and sometimes pain and swelling. Accordingly, one theory is that avoiding caffeine may help women avoid breast cancer.
The problem, however, is that the results from the many different studies that have been done are mixed. Most studies seem to show no connection, but some smaller studies show a weak positive link, while others seem to say that caffeine may (in a small way) help women avoid breast cancer.
Recently the results of a long term study were used to look at the relationship between breast cancer and caffeine intake (Arch Intern Med 208; 168(18):2022-2031). The data came from a cancer-prevention study which lasted over ten years and included over 39,000 women. The researchers compared the caffeine intake of those women who developed breast cancer during the study with the caffeine intake of those women who did not.
After taking into account other risk factors, those women who drank four or more cups of coffee per day tended to have an increased average risk of just 4% - a number that we in the medical field don't consider to be significant.
There were instances where caffeine intake was positively associated with cancer, however. Those women with a history of benign breast disease who also drank four or more cups of coffee per day had about a 35% increase in their risk of breast cancer when compared to those women who never drank coffee. When the researchers looked included all forms of caffeine (tea, chocolate, etc.) the results were similar.
Further, in those women who did develop breast cancer, high caffeine consumption was associated with estrogen and progesterone-receptor negative breast cancers (an increase in risk of about 68%) and breast tumors larger than 2 centimeters (increased risk of almost 80%).
Clearly avoiding caffeine is important for those women with benign breast disease. If you are not otherwise at risk for developing breast cancer, however, go ahead and enjoy your coffee (or tea, or other caffeinated beverage) without worrying about it.
First posted: December 3, 2008