A study that turns conventional thinking on its head shows that in at-risk patients, a cut-off point is reached below which further reductions in blood pressure provide no added benefit.
Researchers looked at data from 4,480 patients with high blood pressure taking part in a heart disease study.
Over a period of 21 years, participants had their systolic blood pressure - the blood circulation pulse coinciding with each heart beat - measured at three-year intervals.
At the same time, cases of heart failure, heart attack, stroke, or death associated with heart disease were recorded.
The study found that lowering systolic blood pressure below 140 millimetres of mercury (mm Hg) was beneficial. But reducing it still more to below the "normal" figure of 120 mm Hg had no further impact on the rate of cardiovascular events.
Lead author Dr Carlos Rodriguez, from Wake Forest Baptist Medical Center in the US, said: "Frequently we treat patients' blood pressure to the lowest it will go, thinking that is what's best.
"Our observational study found that treating to low pressures doesn't provide any benefit to patients with regard to reducing risk of dangerous heart events like heart attack, heart failure and stroke.
"This calls into question the notion that lower is better."
The findings are published in the on-line edition of the journal JAMA Internal Medicine.