Both studies were stopped early so the surprising benefits could be made known. Doctors presented results on Monday at an American College of Cardiology conference in Chicago.

“It is never too late to start” on blood pressure drugs, said Dr Nigel Beckett of Imperial College in London, who led one study in the elderly that also was published online by the New England Journal of Medicine.

“Our idea is, if you have to add on, why not do two right off the bat” in a single pill, said Dr. Kenneth Jamerson of the University of Michigan. He led a study testing a single daily pill combining a diuretic and the ACE inhibitor benazepril versus a daily pill containing benazepril and a calcium channel blocker, amlodipine. ACE inhibitors dilate blood vessels to lower pressure. Calcium channel blockers do the same in a different way.

A total of 11,462 people in the United States and Nordic countries were given one combo or the other. Their average age was 68, and besides high blood pressure they were obese, had diabetes or other health problems. Neither they nor their doctors knew which drugs they were taking until the study was stopped in October after it was clear that people on the ACE-calcium blocker combo were doing better.

Those people had about 20 percent fewer heart-related problems or strokes—526 among the 5,713 in this group versus 650 events among the 5,732 others, Jamerson said. Six months of treatment with either combo brought blood pressure to an acceptable range for 73 percent of patients.

The findings could shape treatment guidelines due to be reviewed in a few months.

Guidelines also may change to reflect a second study that found dramatic benefits for treating people in their 80s, an age when blood pressure drugs were not known to be safe or effective. “The over-80s are the most rapidly expanding segment of our population,” and the prevalence of blood pressure rises as people age, Beckett noted.

His study assigned 3,845 older people in Europe, China and several other countries to take the diuretic indapamide or dummy pills plus the ACE inhibitor perindopril as needed to reach a goal of 150/80 from an average starting pressure of 173/91. The study was stopped last July after monitors saw that those on the diuretic had 39 percent fewer fatal strokes and 21 percent fewer deaths from any cause—benefits far exceeding what researchers predicted.