Introduction

We have run the Highlight on the Home Page of this website for months, under the heading "Prevention and Control America's Blood Pressure - MISSION POSSIBLE". The intent was to encourage people to be aware of the need for keeping their blood pressure under control. We also published a series of articles on the importance of adherence to drug regimes (i.e. taking your medications as prescribed by your physician).

It seems that there is still a problem in achieving blood pressure control universally. This is shown by an article in the Archives of Internal Medicine, which handles both adherence to therapy and the need to intensify it, where necessary. Here's a summary.

What was done

This study was conducted in Colorado, around Denver and Boulder. Patients enrolled in the Kaiser Permanente of Colorado (a health management organization or HMO) were identified as having coronary artery disease, based on hospitalization records and outpatient diagnoses. The HMO has an active clinical pharmacology program that helps primary caregivers and cardiologists with treatment of coronary artery disease.

Patients were included in the study if they had at least 1 year of continuous follow-up with at least 4 blood pressure measurements during this time. Medications prescribed and dispensed were recorded, allowing adherence to be calculated (the total number of days supplied for a drug divided by the observed time interval). Patients were classified as nonadherent based on a PDC (proportion of days covered) of less than 0.80. The time period studied averaged 4.6 years.

The dose of the anti-hypertensive drugs prescribed was also studied. Therapy intensification was defined as a dosage increase for any drug or an increase in the number of anti-hypertensive meds between the first and last 6 months of follow-up.

Uncontrolled systolic blood pressure (SBP) over time was used as the 'outcome measure' to assess what had gone wrong. For analysis, three clinically relevant SBP groups were defined: (1) patients with controlled SBP that remained stable and controlled over time (SBP had to be 140 mmHg or less); (2) patients who started with a high SBP that decreased over time; and (3) patients who started with a high SBP that remained high over time. These groups were termed 'normal-normal', 'high-normal', and 'high-high', respectively.

What was found

There were 9,114 patients (87%) in the normal-normal group, who maintained an average SBP of 127 mmHg over the study period. The high-normal group comprised 779 patients (7.5%); their average SBP fell from 147 mmHg to 128 mmHg by the end of the study. The high-high group had 554 patients (5.3%), with an average SBP of 154 mmHg at the start and 153 mmHg at the end of the study.

For the purpose of the study, the main comparisons were between the high-normal and the high-high groups. Statistical analyses were made that showed both medication nonadherence and failure to intensify therapy were associated with uncontrolled SBP, i.e. the high-high group showed significant differences from the high-normal group with respect to these factors.

After making adjustments for possible interfering factors, such as age, gender, existent diabetes, or cardiovascular disease, it was found that patients who didn't stick to their medication regime - the nonadherents - were 1.73 as likely as the adherents to fail in controlling their blood pressure. Similarly, patients who had no increase in dose or addition of a medication when it was indicated were 1.31 times as likely to have uncontrolled blood pressure.

Conclusions

This study shows what might have been assumed using common sense: if you don't take your medication, or if the medication isn't 'strong' enough, you're unlikely to control your high blood pressure. What's important about the study is the considerable number of hypertensive patients - 5.3% - whose blood pressures remain high over the 4.6 years of the study despite initial attempts at treatment. In other studies, the number of coronary heart disease patients with blood pressure levels above 140/90 mmHg has been recorded as high as 50%. However, in this Kaiser Permanente population, the 'above normal' level at the outset was 12%, and fell to 5.3% after an average of 4½ years.

Clearly, a number of the patients in this study (the 7.5% high-normal), were brought back to the desired level. But there is still much to be done to ensure that all hypertensive patients are brought under control. Nonadherence to a treatment regime is the biggest culprit, but failure of the physician to prescribe adequate medication (i.e. a sufficiently high dose, or addition of another drug) is also a continuing problem.