Missing seven days of hypertension treatment in a six-month period can significantly increase risk of stroke, says the Stroke Association. Research conducted by IMS Health on behalf of the charity compared two groups of patients taking hypertension treatment; 1,550 patients who had had a stroke were compared with 1,547 patients who had not. The persistence with treatment of both groups was assessed during a six month period. It was found that a difference equating to seven missed days of hypertension treatment increased the risk of stroke compared with the control group.