If you are an older woman and, actually, even if you are not an older woman, weight train. Study after study after study have come out showing the significant, and at times incredible, health benefits of strenuous exercise. Exercise that pushes your body a bit and leaves you somewhat sore.
If you're lifting weights, don't just do what's easy. If fifteen pounds is comfortable, move up to twenty. If abdominal curls are easy, hold two five pound weights while you do them. Only a little work each day makes a difference.
I've been trying to get my mom to weight train for years. She won't, of course. So don't be like my mom.
Exercise: In Women, Training for a Sharper Mind (NYTimes.com)