But then, out of the blue, at age 55 (which turns out to be the most common age for it), I had a stroke that landed me in the hospital for 5 days and unable to walk straight. I thought that sort of thing was years down the road for active people like me, who skied hard in the winter, hiked and lifted weights the rest of the year. It turns out cardio-vascular troubles runs in my family (my grandfather and 5 of his brothers and a sister died of heart disease in their 50s. But though they…