The causes of high pressure and low pressure are as follows: 1, the age factor, with increasing age patients will experience a significant increase in systolic blood pressure, diastolic blood pressure decreases therefore will lead to an increase in pulse pressure difference, increase. 2, high pressure and low pressure will be caused by increased peripheral resistance of the blood vessels, the elasticity of the arterial wall is reduced, increased brittleness, usually lead to this aspect of the factors are increased lipids, will gradually form under the intima of the blood vessels atheroma 3, hyperlipidemia, in the role of hyperlipidemia, blood viscosity will increase, blood flow resistance will also increase, which will lead to high pressure, low pressure low, pulse pressure differential becomes large situation.