REN and atherosclerosis: The higher mean SBP achieved within 6 h raises the possibility that renal impairment contributes to the therapeutic resistance to antihypertensive agents through such mechanisms as increased sympathetic activity, alterations in the renin–angiotensin–aldosterone system, vascular aging and atherosclerosis, and sodium dysregulation from reduced functioning nephrons and lowered glomerular filtration rate (29, 30).