Each February, we are reminded about the importance of our heart, one of the body's most vital organs. The human heart is an astonishing machine, pumping 2,000 gallons of oxygen-rich blood over the course of a day, every day, to every cell in the body. The heart's incredibly important role in keeping us alive means that when it fails, we can be in grave danger. Tragically, many women do not recognize that they are at higher risk for heart troubles than their male counterparts.

Thanks to a lot of hard work from the National Heart, Lung, and Blood Institute and its many partners in The Heart Truth® campaign, so many American women are becoming more aware of this health issue that remains the number one killer nationwide of our mothers, daughters, sisters, and friends. That is truly a cause for celebration.

However, our work is far from done. From these statistics, we can see clearly that sex matters when it comes to heart health. But what is behind these numbers? Peeking beyond the curtain of statistics, what is it in a woman's body that makes her more prone to heart disease?

While we know that hormones make women different from men, a range of molecules, systems, and behaviors also differ markedly between females and males. For instance, did you know:

• The blood vessels of women with heart disease look very different up close than the blood vessels of men with heart disease.
• Female adult stem cells in mouse muscle regenerate more easily than do similar cells in male mouse muscle.
• Women are more likely than men to have complications from implantable cardiac defibrillators.
• Women with a history of preeclampsia are 60 percent more likely to have a non-pregnancy related stroke.

All of these issues, and more, are being pursued by scientists through research. Their breadth illustrates that many factors affect the health of women and men differently. By addressing these questions, the NIH Office of Research on Women's Health aims to improve the health of not only women, but of families, communities, and society at large.

There are so many unanswered questions about how the most basic differences between men and women affect our livelihood — indeed, every cell in the female body has a "sex" and as a consequence may work differently than its counterpart in a male body. Understanding what drives basic differences between females and males is a key research question that we are asking through rigorous scientific research.

Stay tuned!