High Blood Pressure Dropouts

Summarized by Robert W. Griffith, MD
January 22, 2007

Summary

A simple questionnaire can help identify non-adherent hypertensive patients who are at risk of increased cardiovascular events and death.

Introduction

Adherence to a medication regimen (which is sometimes called compliance) is defined as the extent to which patients take their drugs as prescribed by their physician. In other words, how closely they follow a prescribed treatment regimen. It's usually reported as the percentage of the prescribed doses of a medication actually taken over a given period.

Adherence to high blood pressure medication is not, in general, very good. There are many reasons for this, but it's largely because hypertension has no symptoms, unless it's very severe. Adequate compliance is considered necessary to achieve the desired blood pressure level. However, even in patients who do take their meds, full control of blood pressure is only achieved in roughly half of them. A recently reported study examined the adherence rates in a 10% sampling of over a million hypertensive patients, along with their resultant blood pressure levels.¹ While 75% of the sample achieved a high level of adherence, only 43% of these attained their blood pressure goal (below 140/90 mmHg, or below 130/85 mmHg if diabetic). Of those that showed medium or low compliance, the blood pressure goal was reached in only 33%.

Most studies of anti-hypertensive regimes, including compliance studies, use the blood pressure level as the desired endpoint. To drive home the point of the need for adherence, an Australian study reported in the Medical Journal of Australia has examined self-reported adherence in relation to major cardiac events or death. Here's a summary.

What was done

The Second Australian National Blood Pressure Study (ANBS2) enrolled patients between 65 and 84 with high blood pressure (above 160 mmHg systolic or 90 mmHg diastolic). The study was primarily a comparison of a diuretic drug ("water pill") with an ACE-inhibitor. A short questionnaire used to determine drug compliance was given to over 6,000 participants. It read as follows:

• Did you ever forget to take your medication?
• Were you careless at times about taking your medication?
• When you felt better, did you sometimes stop taking your medication?
• Sometimes, if you felt worse when you took your medication, did you stop taking it?

Those patients who answered "no" to each question they completed were assigned to the adherent group, and those who answered "yes" to any question formed the non-adherent group.

The rates of all cardiovascular adverse events (e.g. myocardial infarction or heart attack, sudden heart death, stroke, heart failure, or ruptured aortic aneurism), as well as all-cause deaths, were compared between the two groups. In addition, baseline and post-survey blood pressure measurements were compared.

What was found

Questionnaires were returned by over 4,000 participants, and 3,912 of them could be used for the analysis. There were 2,614 (67%) in the adherent group, and 1,298 in the non-adherent group.

The likelihood of an event was expressed as the hazard ratio (HR), which represents the relative risk for the event in two groups, with the value for one group set as 1.0. Thus an adverse event like a heart attack with a HR of 0.80 means that for every 10 people with a heart attack in one group there would be 8 in the other group.

The HRs for adherent patients, compared with non-adherent patients, are given in the table:

Outcome Event	HR
All cardiovascular events or all-cause deaths	0.83
First cardiovascular event (MI, sudden heart death, stroke, etc)	0.81
First non-fatal cardiovascular event	0.81
Fatal other cardiovascular event	0.68
First occurrence of heart failure	0.58

It can be seen that adherent patients are less likely to experience a cardiovascular event or death than non-adherent patients.

Two of the questions seemed to carry more weight than the others. With a "no" answer to "Did you ever forget to take your medication?" HRs of 0.28 to 0.35 were obtained for cardiovascular events under different categories. And for the question "Sometimes, if you felt worse when you took your medication, did you stop taking it?" the risk of first occurrence of heart failure was doubled for those answering "yes".

Comparison of post-survey blood pressures showed that adherent patients had a significantly greater fall in systolic pressure (by an average of 1.4 mmHg) than non-adherent patients. Diastolic pressures showed similar but less marked changes.

What does this mean?

This Australian study shows that a simple questionnaire was able to identify individuals at greater risk of serious, even fatal, cardiovascular events such as heart attack, because of apparent non-adherence to prescribed medication. One question, related to forgetting to take medication, was found to be best at identifying the risk. If this question were to be included in every follow-up visit of a hypertensive patient, one could expected that some patients at risk would be identified, and encouraged to be more compliant in taking their meds - with more favorable health results.

Source

• Self-reported adherence with medication and cardiovascular disease outcomes in the Second Australian National Blood Pressure Study (ANBS2) MR. Nelson, CM. Reid, P. Ryan,  et al., MJA, 2007, vol. 185, pp. 487--489

Footnotes
1. Relationship of blood pressure control to adherence with antihypertensive monotherapy in 13 managed care organizations. TJ. Bramley , PP. Gerbino, BS. Nightengale, F. Frech-Tamas, J Manag Care Pharm, 2006, vol. 12, pp. 239--245

Related Links
Not taking Your Meds Can Be Dangerous to Your Health
Risk of Stopping High Blood Pressure Medication
Don't Stop Taking Your Statin!

Please take a moment to give us your comments. For questions about Health matters you may check our "Questions & Answers" Portal and Service.