Update: Banbury now closed.
Hypertension is one of the causes – cholesterol plaque are deposited along the walls of the arteries, making them harden and constrict. Because the arteries are constricted, the blood exerts great force against the walls of the blood vessels, causing the blood pressure to rise.
Another cause is hardening of the arteries – the arteries narrow due to these same fatty deposits.
Additionally, poor circulation can result from varicose veins that develop because of a loss of elasticity if the walls of the veins.