By: Thomas Pickering, MD, DPhil, FRCP, Director of Integrative and Behavioral Cardiology Program
of the Cardiovascular Institute at Mount Sinai School of Medicine, New York.

In some people high blood pressure can be controlled with a single drug, while others may need three or more. The height of the blood pressure is only one of the factors that determine this, and little is known about what the others are. A large study called INSIGHT has enabled this question to be looked at. Patients were treated with either a calcium channel blocker (nifedipine) or a diuretic, and then a beta blocker (atenolol) or an ACE inhibitor added if the pressure remained elevated. The number of patients was large (5,669), and the treatment schedule was tightly controlled, so that it was possible to examine a number of factors which might predict how easily the blood pressure could be controlled.

The blood average blood pressure was 172/99 mmHg at the start of the study, and 139/82 at the end. About a quarter of the patients had diabetes as well as hypertension. The diabetics started and finished with higher blood pressures than the others, and more of them required a second drug to control the blood pressure (35% versus 28%). One other factor that appeared to influence the ease of controlling the blood pressure was systolic hypertension (a diastolic pressure less than 90 mmHg) as compared to diastolic hypertension(diastolic above 90). Patients with systolic hypertension needed slightly less drugs to control their pressure (27% needed a second drug, as compared to 31% of those with diastolic hypertension). Some other factors were looked at, but they did not affect the ease of controlling the blood pressure; they included age, gender, smoking, high cholesterol, and the presence of atherosclerosis. The diastolic pressure tended to fall a little more in women and in older patients, however.

Doctor’s comments

The major goal of this study (INSIGHT) is to see of a calcium channel blocker will lower the cardiovascular event rate more than a diuretic-based treatment, and this report represents an interim analysis-the study is still in progress. The reason why diabetes should make the blood pressure harder to control is not clear, but does have important implications. Paradoxically, the official goal for treating hypertension is now lower (130/85) if diabetes is present than if it is not (when the goal is 140/90), although for INSIGHT the same goal blood pressure was used for everyone. So there are two reasons why diabetics are likely to end up taking more antihypertensives than non-diabetics-the lower goal blood pressure, and the poorer response to treatment.

Where it was published

MJ Brown and colleagues. Influence of diabetes and type of hypertension on response to antihypertensive treatment. Hypertension 2000; 35: 1038.