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A group of researchers<ref>None of the researchers hold positions in oncology (the branch of medicine that studies cancer), and one of the researchers is a nutritionist.</ref> at the Harvard School of Public Health and Harvard Medical School, operating under a government research grant, published a report on research they conducted concluding that a group of relatively young nurses show no increased incidence of [[breast cancer]] from [[abortion]].<ref>The full text of the study is available for a $15 charge at http://archinte.ama-assn.org/cgi/content/full/167/8/814</ref>

A group of researchers<ref>None of the researchers hold positions in oncology (the branch of medicine that studies cancer), and one of the researchers is a nutritionist.</ref> at the Harvard School of Public Health and Harvard Medical School, operating under a government research grant, published a report on research they conducted concluding that a group of relatively young nurses show no increased incidence of [[breast cancer]] from [[abortion]].<ref>The full text of the study is available for a $15 charge at http://archinte.ama-assn.org/cgi/content/full/167/8/814</ref>

The average age of diagnosis of breast cancer in America is 61 years old.<ref>http://www.webmd.com/breast-cancer/news/20050922/fewer-american-women-dying-of-breast-cancer</ref>  But the average age of participants in this study who had an abortion was only 42 years old,<ref>Michels K. Induced and Spontaneous Abortion and Incidence of Breast Cancer Among Young Women. Arch. Inter. Med. 2007;167:816 (Table 1).</ref> too young for the average person to develop breast cancer. This age disparity is analogous to an attempt to draw conclusions about heart disease by studying teenagers.  

The average age of diagnosis of breast cancer in America is 61 years old.<ref>http://www.webmd.com/breast-cancer/news/20050922/fewer-american-women-dying-of-breast-cancer</ref>  But the average age of participants in this study who had an abortion was only 42 years old,<ref>Michels K. Induced and Spontaneous Abortion and Incidence of Breast Cancer Among Young Women. Arch. Inter. Med. 2007;167:816 (Table 1).</ref> too young for the average person to develop breast cancer. This age disparity is analogous to an attempt to draw conclusions about heart disease by studying teenagers. Furthermore, based on the definition of "average", 50% of breast cancer patients would have been diagnosed at an age ''older'' than 61. When added to the patients diagnosed between ages 42-61, a very large portion of breast cancer patients are not included.  

However, the authors of the Harvard study asserted that earlier studies that reported that abortion increases the risk of breast cancer had been carried out "largely" on premenopausal women.<ref>''Id.'' p. 820.</ref> This study is ''ongoing'' or ''longitudinal'' rather than retrospective, because young persons are monitored before they develop health problems rather than studying them after they develop health problems. There are advantages and disadvantages to both types of studies.

However, the authors of the Harvard study asserted that earlier studies that reported that abortion increases the risk of breast cancer had been carried out "largely" on premenopausal women.<ref>''Id.'' p. 820.</ref> This study is ''ongoing'' or ''longitudinal'' rather than retrospective, because young persons are monitored before they develop health problems rather than studying them after they develop health problems. There are advantages and disadvantages to both types of studies.