**15. Sex differences in the transition from reproductive to post-reproductive stage**

In one of the previous sections we provided evidence that women oxidize fatty acids, which are the predominant energy source at all ages, at a slower rate in comparison with men, and thus probably produce ROS at a slower rate [116–118]. Olivetty et all. [111] studied changes in mononucleated and binucleated myocytes with age in enzymatically dissociated cells. The age interval examined varied from 17 to 95 years. The authors have found that in the course of aging women's hearts preserved the ventricular myocardial mass, aggregate number of mononucleated and binucleated myocytes, average cell diameter and volume. In contrast, in the men's hearts the authors observed nearly 1 g/year loss of myocardium, and this phenomenon accounted for the loss of approximately 64 million cells. These detrimental events involved the whole male's heart. In the remaining cells, myocyte cell volume increased at a rate of 158 microns3/year in the left and 167 microns3/year

#### *Update in Geriatrics*

in the right ventricle. And these changes in the men's hearts were linear from the age of 17 to 95, whereas in women the structural properties of the heart remained unchanged [111]. Thus, it seems that women enter the post-reproductive stage with relatively "young" heart, whereas in men the aged heart lost many cells and the remaining cells increased their volume, which is a disadvantage for the heart's energy metabolism.
