Why Are We Doing So Badly with the Control of Hypertension? Poor Compliance Is Only Part of the Story

Treating hypertension should be a simple matter, but it is not. We know beyond any doubt that lowering blood pressure can substantially reduce the risk of stroke and heart attack. More than 100 different drugs are available for its treatment; all have proven efficacy, most have few side effects, and many are formulated for once‐daily dosing. Why, then, are the reported rates of blood pressure control so disappointing, and apparently not getting any better?

The official figures are derived from the National Health and Nutrition Examination Surveys (NHANES), conducted at regular intervals in random samples of the population. The latest survey, in 1991–1994, ¹ revealed that only 27% of hypertensives had blood pressures controlled to below the target level of 140/90 mm Hg; this figure was 29% in 1988–1991. In contrast, figures provided by the American Heart Association show that the expenditure for antihypertensive drugs has increased dramatically over the past few years. What is going on? We in the United States are not alone in this respect: statistics from numerous other countries show that control rates are, if anything, worse overseas: In France and Germany, which by some accounts have health care systems in many ways superior to ours, the rates are even lower. ² , ³

The easy rationalization is to blame our patients, on the grounds that they refuse to take their pills. While there may be some truth in this, it is by no means the whole story, nor is it necessarily the most important part of the story. One survey found that 70% of doctors attributed treatment failures to poor compliance by their patients, while 81% of patients regarded their compliance as good. ⁴ Two other factors that we must consider are the health care providers (primarily physicians) and the system in which we operate. Given the incontrovertible importance of this problem, surprisingly little is being done to solve it.

Compliance, for the purpose of this essay, may be defined as the frequency with which a patient actually takes his or her medication as prescribed. Problems concerning compliance with medical regimens are as old as the history of medical therapy. In fact, Hippocrates complained that “…patients are often lying when they say they have regularly taken the prescribed medicine.” ⁵ As long as there were practically no pharmacologically effective therapies, poor compliance was a negligible problem. Today, however, with medication available that effectively controls blood pressure, the problem has become a major one.

The importance of compliance is underscored by three studies that have documented the association between poor compliance and higher mortality. ⁶ , ⁷ , ⁸ This may not seem surprising, but in each of these studies the effect was observed in the placebo group as well as in the active treatment group. All three study populations were high‐risk cardiac patients; the study drug was added to the patients' other medications, so one possible explanation is that the other pills the patients were supposed to be taking may have influenced mortality. Another is that patients with a more positive attitude toward life have a better prognosis.

METHODS OF MEASURING COMPLIANCE

One problem in this field is quantification of patients' compliance. The simplest method is, of course, to ask them if they have taken their medications regularly. Not surprisingly, this is not very reliable, since patients tend to tell us what we want to hear. A more objective way is to measure blood levels of medications. This is not feasible for antihypertensive drugs, although measurement of blood cotinine (a metabolite of nicotine) is the standard way of assessing compliance with smoking cessation. There is also the problem of the “toothbrush” effect, in which patients begin brushing their teeth a few days before a dental appointment, but this may not provide evidence concerning longer‐term compliance. The use of pharmacy records as a measure of compliance is another objective measure. If it can be established which pharmacy the patient uses, and; if the prescription was not filled, it can be assumed that the patient did not take the prescribed medication. Pill counts probably have been used most frequently, but this method is susceptible to the practice of “pill dumping,” whereby patients empty their pill bottles just before they are due to be counted. Analysis of the various methods of quantifying compliance have shown about 70% agreement among them. ⁹

An exciting development in compliance assessment is electronic monitoring, in which the times and dates of bottle opening are recorded in a microchip embedded in the cap. While these are used only in clinical studies, they provide the most objective information as to how regularly patients take their medication. One of the first surveys in which these devices were used ¹⁰ showed that compliance fell off markedly as the complexity of the pill regimen increased: with once‐daily dosing it was 87%, but with four daily doses it was only 39%. A subsequent study ¹¹ revealed that compliance declined between visits: it was 87% at the time of the index visit, but only 67% 1 month later. The largest such study ¹² included 2173 hypertensive patients who took part in a drug trial for 2 months, and who knew that their compliance was being monitored electronically. Despite that knowledge, approximately one third were classified as “poor compliers,” defined as having missed or delayed more than 20% of their doses. Predictors of poor compliance included younger age, living in a city rather than outside it, and smoking. Of course, if the patient's blood pressure is controlled without his or her taking the full prescribed dosages, it may be that too much has been prescribed. ¹³

One of the reasons for the difficulty in measuring compliance is the Hawthorne effect: the monitoring of compliance will itself affect compliance. In a study of patients with resistant hypertension, all of whom had been prescribed three medications, it was found that simply introducing electronic monitoring of their medication use resulted in a significant improvement in blood pressure. ¹⁴ During the first month of monitoring, with no change in medications, the average compliance was 93%, but the blood pressure fell from 156/106 to 146/99 mm Hg. The results also suggested that electronic monitoring may be used as both a therapeutic and diagnostic procedure.

DETERMINANTS OF COMPLIANCE

It might be assumed that side effects from medications are a major cause of noncompliance, but in practice this does not appear to be the case. There is some evidence that a simpler pill regimen improves compliance, and most of the antihypertensive medications in current use are effective in once‐daily dosage.

The most important predictors of compliance appear to be psychosocial factors and include patient satisfaction, psychosocial adjustment to illness, social support, and health status. ⁹ Depression is associated with poor compliance. An important advance in our understanding of patients' willingness to change their behavior is the “stages‐of‐change” model, ¹⁵ which classifies patients into five different categories: precontemplation (is not interested in making the required changes), contemplation (intends to make the change within the next 6 months), preparation (intends to make the change within the next month), action (has recently made the required change), and maintenance (has adhered to the prescribed behavior for more than 6 months). Not surprisingly, this measure explains a large proportion of individual differences in compliance: in one study, 72% of the variance in compliance could be explained by the stages of change, and inclusion of all the other potential variables increased the figure to only 74%. ¹⁶

WHAT CAN BE DONE TO IMPROVE COMPLIANCE?

A host of techniques have been attempted in the effort to improve compliance, with very mixed results. Part of the problem may be that the measures of compliance used to evaluate these techniques have not been reliable. For example, many studies relied on pill counts. The interventions that have been used have been focused mainly on making life easier for the patients, or removing barriers. Examples include calendar packaging (e.g., blister packs with each pill labeled with the date when it should be taken), simplified dosing regimens, and cards on which patients record each dose. All of these approaches have resulted in some improvement. Several trials have employed patient education and counseling, with generally inconsistent results. Physician education and worksite‐based care also seem to improve compliance. Self‐monitoring would seem to be an obvious way of enhancing patients' involvement with their care, but so far the results have been very mixed.

Two meta‐analyses ¹⁷ , ¹⁸ have examined strategies for improving compliance. In the first, Roter et al. ¹⁷ examined 153 studies and concluded that no single strategy was most effective. In general, the more comprehensive the intervention, the better the chance of success. An example of this is found in a study by Haynes et al., ¹⁹ who utilized a variety of techniques, including home monitoring, education, and reinforcement. Compliance (measured by pill counts) increased from 45% to 66% in the experimental group, and remained at 45% in the control group. The intervention also doubled the number of patients whose blood pressure met the criteria for control.

IT'S NOT ALWAYS THE PATIENT'S FAULT

Blaming the patient for poor blood pressure control may be an easy explanation, but it is not always accurate. For one thing, the response rate to individual medications is typically no higher than about 50%, and unfortunately we have no reliable means of knowing which patient will respond best to which medication. ²⁰ The traditional system of seeing the patient every few weeks or months for a blood pressure check is an extraordinarily inefficient one for several reasons. We know that the readings obtained in the clinic often do not represent the patient's true blood pressure; moreover, it is inconvenient for the patient to make multiple visits for medication changes or titration. It is hardly surprising that patients become disillusioned.

Also, physicians do not always take hypertension control seriously. An analysis of the treatment of hypertension at a Veterans Administration clinic ²¹ disclosed that doctors often saw patients with poorly controlled hypertension, but made no recommendation for improving it. An example of what can be done when both patients and health care providers are motivated is provided by the Controlled Onset Verapamil Investigation of Cardiovascular End Points (CONVINCE) study, a multicenter trial to compare the effects of verapamil and conventional treatment (β blockers and diuretics) on cardiovascular morbidity. ²² At entry, only 20% of patients had adequate blood pressure control, but during the first 2 years this figure increased to about 70%. The authors of this trial attributed this excellent result to the use of a forced titration strategy, plus medications “…provided without charge to motivated subjects by well‐trained healthcare workers.” Results of the ALLHAT trial also indicate better blood pressure control with increasing efforts on the part of the health care provider.

WHERE DO WE GO FROM HERE?

Introduction of new medications is not, in itself, going to solve this issue; as shown by the CONVINCE results, excellent control can be achieved with the agents we now have. We need better ways of finding the right medication(s) for each patient, and for monitoring their effects. The long‐term control of blood pressure requires an ongoing partnership between the patient and the health care provider (who does not have to be a physician). Both parties must be educated and motivated, and this entails communication on a regular basis. A major cause of the present problem is that the traditional method of treating hypertension, with infrequent clinic visits and virtually no communication between them, is very poorly suited to achieving this. The advent of the information age holds enormous promise; with the use of self‐monitoring and telemedicine it is possible to monitor blood pressure and transmit the readings electronically at regular intervals, and also to maintain regular communication without the expense, inefficiency, and inconvenience of clinic visits. Assessment of compliance is not a problem, because failure to send the readings would prompt a message from the health care provider. Hope is just around the corner.