What are the worst health challenges for seniors?

Several. It all depends on the health problems the seniors have. They may have problems with.Cognition, visual and hearing problems, incordination, decreasing motor skills, loss of independence, depression - these are some of the things they face in late life.
Challenges. Weakening of the heart and/or brain. Most people today will die from some complication of the heart or brain. Healthy diet and exercise are key!