A blood pressure differential between 30-60 mmHg is normal for people. Some people have specific diseases that can cause the differential pressure to become larger or smaller. The reasons for this are: First, increased peripheral vascular resistance leads to a smaller differential pressure. The resistance to blood flow from the aorta to the periphery increases, resulting in an increase in the amount of blood in the aorta causing an increase in diastolic pressure and a decrease in differential pressure. Second, increased heart rate leads to a smaller pressure difference. In this case, the diastolic period of the heart is shortened, and the amount of blood flowing from the aorta to the periphery during diastole is reduced, causing an increase in diastolic pressure and a smaller pressure difference. Third, aortic valve insufficiency, due to the presence of aortic regurgitation leads to an increase in systolic pressure, a decrease in diastolic pressure, and an increase in differential pressure. Fourth, atherosclerosis, due to the decrease in the elasticity of the aorta, can also cause an increase in systolic pressure, a decrease in diastolic pressure, and an increase in differential pressure.