What is the trend in sickle cell anemia?

Who will have it bad. The trend currently is trying to find out why some people have very little problems and others can be so troubled by this disease. In some, the disease will cause strokes, lung problems, leg ulcers etc. If we knew early on who would have it bad, maybe treatments could be given earlier to prevent these problems. But not everyone has it bad, so it is hard to know.