This microscope image shows the 46 human chromosomes, blue, with telomeres appearing as white pinpoints. Research released on Tuesday, July 16, 2019 offers some of the first biological clues to why women may be more likely than men to develop Alzheimer's disease, and how this most common form of dementia varies by gender. (Hesed Padilla-Nash, Thomas Ried/National Cancer Institute/National Institutes of Health via AP)