MRC Trial of Treatment in Elderly Hypertensives

The MRC trial was a random control comparison of placebo treatment with two active drug regimens: atenolol 50 mg daily and a combined tablet containing hydrochlorothiazide 25 mg and amiloride 2.5 mg. The trial was based on 226 general practices in the U.K. Its primary purpose was to determine whether hypotensive drug treatment in men and women aged 65-74 with systolic pressure in the range 160-209 mmHg and with diastolic pressure below 115 mmHg reduced stroke, coronary heart disease (CHD) and all-cause mortality. A secondary objective was to determine whether outcome differed with the two forms of active treatment. 4,396 patients were randomized: 50% to placebo; 25% each to the two forms of treatment. During the following 5.8 years 25,000 patient-years of experience accumulated. Blood pressure fell in the placebo group, larger falls occurred with the two active treatments. Active treatment (diuretic and beta-blocker groups combined) reduced stroke by 25% (95% CI 3 to 42%), CHD by 19% (-2% to 36%, p = 0.08), cardiovascular events by 17% (2% to 29%). Benefits were clearest for the diuretic regime: a 31% reduction of stroke events, a 44% reduction of CHD and a 35% reduction of cardiovascular events--all significant.