What causes BP in a 75 year old to rise 20+ points top and bottom num. When she sit up & walk and goes down when she lay down? Had a stoke 30 yrs. Ago

BP varies. Blood pressure often is lowest when lying down. On standing it may rise or fall in different people. Official blood pressure is in the sitting position but if blood pressure rises extremely when standing, increase in medication dose is needed. Therefore when on treatment it's best to check BP in both arms sitting and standing.