predictors of persistence with antihypertensive therapy: results from the nhanes

Copyright © 2008 Society for Heart Attack Prevention and Eradication. All Rights Reserved.

Predictors of Persistence With Antihypertensive

Therapy: Results From the NHANES

Leonelo E. Bautista

This study was funded by the American Heart Association, Award No. 0675049N.

Bautista LE, Am J Hypertens 2008 21;2:183-188


Background• Only 57% of known hypertensive patients receiving

pharmacologic treatment in the United States have their blood pressure controlled.

• It is estimated that 15% of all cases of acute myocardial infarction and 32% of all strokes among subjects treated for hypertension can be attributed to uncontrolled blood pressure.

• Failure by patients to use medications as prescribed is considered a major contributor to poor control of hypertension

• 32–53% of newly treated hypertensives stop using their medication by the end of the first year of treatment.



Background• Previous studies of non-adherence are of limited generalizability

because:

they included mostly middle-aged and elderly patients enrolled in a single health insurance

they provided little data on the effects of enabling factors (health insurance, income, and use of health services)

the pattern of medication prescription and use has likely changed as a consequence of increasing awareness, new practice guidelines, and availability of newer drugs with fewer side effects



Background• The objective of this study was to evaluate how the following

factors affect persistence with antihypertensive medication:

a) Predisposing factors (those that describe the propensity of patients to comply): age, gender, ethnicity, education, marital status, language, alcohol intake, and smoking

b) Enabling factors (those that comprise the resources available to help patients in obtaining health care and medications): average family annual income, having health insurance, and visits to the doctor during the last year

c) Need characteristics (factors that reflect the patients’ requirements for care and medication): body mass index, self-reported health status, and coexisting chronic disease



Methods

• Analyses in this study were based on data from NHANES III (1988–1994), NHANES 1999–2000, and NHANES 2001–2002.

• The study sample included NHANES participants who reported they had been diagnosed with hypertension and advised by their physicians to use antihypertensive medication (n = 6,733).

• Participants who were not taking antihypertensive medication and had normal blood pressure during the physical exam were excluded (n=571)



Methods

• Trained NHANES interviewers verified the medications being used during the 30 days prior to the survey date by direct inspection of medication containers.

• Individuals who did not use antihypertensive medication during the 30 days prior to the interview were classified as non-persistent.

• Individuals with diseases that require regular and persistent use of medications were classified as having a chronic disease: arthritis, stroke, emphysema, cancer, asthma, bronchitis, diabetes, or acute myocardial infarction.



Methods

• All analyses were statistically weighted to:

maintain the representativeness of the sample for the US population

avoid selection bias, and correctly estimate the precision of regression coefficients.

• Multiple imputation was used to fill out missing values (10 imputed data sets) to:

avoid selection bias due to the exclusion of subjects with missing data

retain subjects with missing values in the analysis so that the sum of the sampling weights equals the population size



Methods

• Multiple logistic regression with sampling weights was used to estimate the independent effect of each factor on non-persistence

• The first imputed data set was used for model building and variable selection

• The resulting model was applied to the remaining data sets and then the estimates from all datasets were averaged



Results

Predisposing characteristics by persistence with antihypertensive medication (NHANES)___________________________________________________________________________

Persistent Non-persistent p(n=5197) (n=903)

___________________________________________________________________________Age (mean) 62.0 (61.3, 62.6)* 55.3 (53.2, 57.5) <0.001Male gender (%) 40.6 (38.6, 42.6) 51.0 (46.1, 55.9) <0.001Race (%) 0.013 White 76.8 (73.8, 79.7) 69.2 (63.4, 74.9) Black 14.2 (11.6, 16.8) 17.9 (13.4, 22.3) Hispanic 5.3 (3.5, 7.2) 8.4 (4.9, 11.9) Other 3.7 (2.6, 4.8) 4.6 (1.3, 7.8) Education (%) 0.012 Less than HS† 31.9 (29.8, 34.0) 38.0 (32.4, 43.6) HS Diploma 29.6 (27.4, 31.8) 31.6 (26.3, 37.0) More than HS 38.5 (36.1, 40.9) 30.4 (25.2, 35.5)Alcohol drinks/day ≥2 (%) 42.0 (38.7, 45.2) 56.4 (48.7, 64.0) 0.007Current smoker 15.4 (14.1, 16.7) 25.6 (21.5, 29.7) <0.001_____________________________________________________________________________* Figures in parenthesis are 95% confidence intervals; † HS: High school


Results

Enabling and need characteristics by persistence with use of antihypertensive medication

___________________________________________________________________________ Non-persistent Persistent p-value___________________________________________________________________________Low income* (%) 72.8 (70.4, 75.3)† 84.3 (79.6, 89.0) 0.003No health insurance (%) 5.2 (4.1, 6.4) 14.8 (11.2, 18.5) <0.001No medical visits last year (%) 2.00 (1.6, 2.4) 19.4 (15.0, 23.8) <0.001Body mass index (mean kg/m2) 30.4 (30.0, 30.7) 30.4 (29.0, 31.8) 0.946Health Status (%) 0.122 Excellent 7.3 (6.1, 8.5) 6.9 (4.6, 9.2) Very good 22.6 (20.9, 24.3) 19.6 (15.1, 24.2) Good 37.3 (35.3, 39.3) 44.2 (39.5, 48.9) Fair 24.1 (225, 25.8) 21.8 (17.5, 26.0) Poor 8.7 (7.4, 10.0) 7.4 (4.9, 10.0)With chronic disease (%)‡ 67.8 (65.6, 70.0) 55.4 (48.4, 62.4) 0.006___________________________________________________________________________*Family income <$55,000/year; †Figures in parenthesis are 95% confidence intervals; ‡Arthritis, stroke, emphysema, cancer, asthma, bronchitis, diabetes, or myocardial infarction



Results

Multivariate adjusted odds ratios for non-persistence with antihypertensive therapy.______________________________________________________Risk factor Odds ratio (95% CI) p______________________________________________________Age (years)

≥50 1.0040 - 49 2.30 (1.54, 3.44) <0.00130 - 39 2.61 (1.69, 4.02) <0.001<30 12.1 (4.25, 34.56) <0.001

Male gender 1.31 (1.07, 1.61) 0.011Race

Other 1.00Hispanics 1.43 (1.05, 1.94) 0.027

______________________________________________________



Results

Multivariate adjusted odds ratios for non-persistence with antihypertensive therapy.______________________________________________________Risk factor Odds ratio (95% CI) p______________________________________________________Low income* 1.96 (1.35, 2.83) <0.001

No health insurance 1.88 (1.24, 2.83) 0.002

No medical visits last year 10.36 (6.59, 16.29) <0.001

1999-2002 vs. 1988-1994 0.73 (0.55, 0.96) 0.019 ______________________________________________________*Family income <$55,000/year



Conclusions• Non-persistence with antihypertensive medication increased

significantly with young age, in men, and among Hispanics.

• This study also shows that non-persistence is considerably increased in individuals with financial barriers to access health care.

• Low income, having no health insurance, and not visiting the doctor during the last year accounted for more than 50% of the cases of non-persistence.



Implications• Policies that improve access to health care and patient follow-

up may be of great importance in maintaining long-term persistence with antihypertensive medication.

• Efforts to improve compliance should be focused on young patients, men, and Hispanics.


predictors of persistence with antihypertensive therapy: results from the nhanes

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