Final answer:
Ischemic heart disease is the leading cause of death for sickle cell patients in the US, while cancer is the leading cause of death worldwide.
Step-by-step explanation:
The leading cause of death for sickle cell patients in the US is ischemic heart disease. This is primarily due to a sedentary lifestyle and high trans-fat diets. In higher-income countries, however, cancers of all types combine to be a higher overall cause of death. Cancer accounts for twice as many deaths as cardiovascular disease in higher-income countries.