Relationship between Blood Pressure and Death among Treated Hypertensive Patients at the High and Low Ends of Blood Pressure Control

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The summary below is from the full report titled "J-Shaped Relationship between Blood Pressure and Mortality in Hypertensive Patients: New Insights from a Meta-Analysis of Individual-Patient Data." It is in the 19 March 2002 issue of Annals of Internal Medicine (volume 136, pages 438-448). The authors are F Boutitie, F Gueyffier, S Pocock, R Fagard, and JP Boissel. The summaries may be reproduced for not-for-profit educational purposes only. Any other uses must be approved by the American College of Physicians–American Society of Internal Medicine.

What is the problem and what is known about it so far?

Treatment of high blood pressure (hypertension) reduces the risk for heart attacks and death from cardiovascular disease. However, even people whose treatment has been effective remain at increased risk for death compared with persons without hypertension. Researchers have considered the possibility that although moderate reductions in blood pressure can save lives, further reductions may actually increase the death rate.

Why did the researchers do this particular study?

To find out whether decreasing blood pressure could be harmful in hypertensive patients.

Who was studied?

To create the study group for this analysis, the authors placed into one large computer file the study records of 40,233 hypertensive patients who had participated in seven different randomized clinical trials of treatment. Some of the patients had received medication (treated group) and some had received placebo (control group).

How was the study done?

The authors analyzed individual-patient data from all seven studies. In these studies, blood pressure had been measured at least once per year, and patients had been monitored for 2.2 to 5.8 years. The researchers recorded when a patient died of cardiovascular disease or other causes during the study period. They then calculated the risk for death in groups of patients with low, medium, and high blood pressure while they were receiving medication.

What did the researchers find?

1655 participants died during the follow-up period (56% died of cardiovascular causes and 44% died of noncardiovascular causes). On average, patients in the treated group had a lower diastolic blood pressure (the lower blood pressure value) than that of the control group. Death rates from all causes were higher in persons with high diastolic blood pressure and persons with low diastolic blood pressure than in persons in the middle range. This was seen in both treated and untreated patients. The death rate from noncardiovascular causes was particularly high in control patients with lower diastolic blood pressure. The researchers found no evidence of an increased risk for cardiovascular death with low systolic blood pressure (the higher number in the blood pressure measurement) in treated patients.

What were the limitations of the study?

Because the researchers did not measure other health factors affecting the patients, they could not test the possibility that poor general health, which itself is known to decrease blood pressure, might have increased the risk for death.

What are the implications of the study?

The increased risk for death seen in patients with low blood pressure is not likely to be related to excessive treatment because increased risk was also seen in untreated patients.