Risk Factors for Nonadherence to Antihypertensive Treatment

Abstract

Nonadherence to antihypertensive treatment is a critical contributor to suboptimal blood pressure control. There are limited and heterogeneous data on the risk factors for nonadherence because few studies used objective-direct diagnostic methods. We used high-performance liquid chromatography-tandem mass spectrometry of urine and serum to detect nonadherence and explored its association with the main demographic- and therapy-related factors in 1348 patients with hypertension from 2 European countries. The rates of nonadherence to antihypertensive treatment were 41.6% and 31.5% in the UK and Czech populations, respectively. Nonadherence was inversely related to age and male sex. Each increase in the number of antihypertensive medications led to 85% and 77% increase in nonadherence (<0.001) in the UK and Czech populations, respectively. The odds of nonadherence to diuretics were the highest among 5 classes of antihypertensive medications (≤0.005 in both populations). The predictive model for nonadherence, including age, sex, diuretics, and the number of prescribed antihypertensives, showed area under the curves of 0.758 and 0.710 in the UK and Czech populations, respectively. The area under the curves for the UK model tested on the Czech data and for the Czech model tested on UK data were calculated at 0.708 and 0.756, respectively. We demonstrate that the number and class of prescribed antihypertensives are modifiable risk factors for biochemically confirmed nonadherence to blood pressure-lowering therapy. Further development of discriminatory models incorporating these parameters might prove clinically useful in assessment of nonadherence in countries where biochemical analysis is unavailable.

Systolic Blood Pressure and Biochemical Assessment of Adherence

“…Complete non-adherence defined by lack of detection of any prescribed antihypertensive medications ranged from 10% to 54% in studies conducted in specialty clinics or clinical trials. 31–38 Among patients who described themselves as adherent, ~33% were completely non-adherent according to therapeutic drug monitoring, 32, 35 which is similar to our findings of 32% complete non-adherence among the 202 patients who reported being adherent by the ARMS in the current study. The difference of ~20 mm Hg between adherent and non-adherent patients prescribed ≥3 antihypertensives in the current study is also similar to the 18 mm Hg difference between adherent and non-adherent patients referred to a hypertension specialty clinic.…”

“…There was, however, no detectible difference in blood pressure by adherence among patients prescribed fewer than three antihypertensive medications. While this is the first study to use a blood assay to measure antihypertensive adherence in an ED setting, patterns of adherence by number and class of prescribed antihypertensive medications and the relationship between adherence and SBP were similar to previous studies conducted in outpatient specialty clinics and among patients with resistant hypertension, 27–38 supporting the validity of our findings.…”

“…In post-hoc analyses, patients prescribed HCTZ had 2.7 (95% CI 1.5 to 4.9) greater odds of non-adherence compared to patients who were not prescribed HCTZ after adjusting for age, sex, race, insurance, health literacy, numeracy, and education, which is similar to recent work conducted in hypertension clinics. 38 Urinary frequency, orthostatic hypotension, and sexual dysfunction may contribute to the estimated 44.2% non-adherence to hydrochlorothiazide 37,38 and oral clonidine’s dosing frequency is an independent risk factor for non-adherence. 42 Though adherence to ACE inhibitors is generally better than other antihypertensive classes, 50% adherence to ramipril is similar to adherence measured by a urine assay among patients with resistant hypertension in a clinical trial.…”

“…Therapeutic drug monitoring of medication concentrations in urine and blood as a measure of adherence is becoming more widely available, 27–38 and understanding and using results therapeutic drug monitoring is relevant to a wide range of clinicians. Complete non-adherence defined by lack of detection of any prescribed antihypertensive medications ranged from 10% to 54% in studies conducted in specialty clinics or clinical trials.…”

Nonadherence in patients with hypertensive emergency or hypertensive urgency

“…Patients with hypertensive crisis were in 24% completely and in 34% partially nonadherent with 89% taking less than 50% of their prescribed antihypertensive drugs. 13,14 Use of the smallest effective doses in order to prevent adverse effects of antihypertensive medication should also improve treatment adherence. A remarkable additional finding was the high number of blood pressure rising medication and adverse food intake, specifically 33% of patients reported NSAID intake (73% not prescribed, but over-the-counter medication), 8% glucocorticoid intake, 10% antidepressants use, as well as 92% caffeine, 20% nicotine, and 10% licorice consumption.…”