Identification of psychosocial factors which influence patient adherence with an ti h ypertensive medication C. LENNON, C. M. HUGHES, G. D. JOHNSTON and J. C. McELNAY Introduction It is estimated that only 50 per cent of hypertensive patients adhere to medication regimens well enough to be bring their blood pres- sure within recommended limits.’ Many psychological theories have been used to predict adherence be- haviour, with mixed results. Self-effi- cacy may be defined as-a perception that one will be able to perform a giv- en behaviour to produce a certain outcome.2 The theory of planned be- haviour, based on the theory of rea- soned action,3 examines the role of patients’ attitudes, social pressure, perceptions of control and intentions in predicting adherence behaviour. Neither self-efficacy, nor the theory of planned behaviour, has previously been applied to the prediction of non- adherence in the area of hypertension. The study’s aim was to identify psy- chosocial, demographic, and medical factors (eg, other illness and pre- scribed medication) associated with good medication adherence in hyper- tension patients. Method A questionnaire measuring self-efficacy and the variables in the theory of planned behaviour (inten- tions, attitude, subjective norms and perceived behavioural control) was developed to identify psychosocial factors believed to impact on patient adherence. Patients were recruited at an outpatient hypertension clinic, and the questionnaire was administered by face-to-face interview. Adherence with the therapeutic regimen was as- sessed using self-report and blood pressure control (obtained from chart review). When data collection is completed, patient medication records will also be obtained from the community phar- macist and GP, as a third measure of adherence. In this study, the relation- ship between the factors believed to impact on adherence and adherence behaviour were identified using Mann-Whitney tests, logistic regres- sion, and multiple regression analysis. Results To date, 117 patients have completed the questionnaire. Of these, 20.5 per cent (n=24)reported non-ad- herence, and 56.4 per cent (n=66)had less than optimal blood pressure con- FOCAL POINTS 17 It is estimated that only 50 per cent of hypertensive patients adhere to medication regimens 0 In this study evaluation of self-efficacy and the theory of planned behaviour was used to identify psychosocial factors which impact on patient adherence to antihypertensives 0 High self-efficacy, intentions to comply with the medication regimen, possessing a positive attitude towards taking medication, perceiving pressure from significant others to take medication as prescribed, and perceiving control over taking medication were determinants of good adherence 0 The successful identification of factors which influence adherence will allow health-care providers to implement interventions, aimed at enhancing adherence with antihypertensive medication trol, as determined by British Hyper- tension Society guidelines.4 Using self- report as a measure of adherence, a statistically significant difference was evident in self-efficacy scores between adherent and non-adherent patients (P<0.001), with adherent patients ob- taining higher scores on the self-effi- cacy scale. All variables in the theory of planned behaviour were entered into a stepwise logistic regression. Consistent with the theory, analysis showed that intentions and perceived behavioural control were the only variables that significantly contribut- ed to predictions of self-reported ad- herence with prescribed medication (P<O.OS).Multiple regression analysis indicated that intentions to adhere with the drug regimen were explained by attitudes, subjective norms and perceived behavioural control (43 per cent variance explained). Analysis failed to identify any significant dif- ferences in demographic or medical factors between the adherent and non- adherent groups. Discussion Understanding the mecha- nisms behind patient adherence and the factors that influence it is an im- portant objective in hypertension management. Self-efficacy and the theory of planned behaviour have provided descriptions of some deter- minants of adherence with medication in this population of hypertensive patients. Preliminary analysis indicates that high self-efficacy and intentions to comply with medication predict ad- herence behaviour, while intentions to comply with medication appears to be determined by having a positive atti- tude to taking medication as pre- scribed, perceiving pressure from significant others to take medications as prescribed and perceiving control over taking medication. However, the discrepancy between the number of patients reporting non-adherence with medication (1x24) and the number of patients possessing less than optimal blood pressure control (n=66) sug- gests that the self-report measure may not accurately represent the extent of non-adherence in this population. The identification of factors that predict non-adherence in hypertensive patients would allow health-care providers to implement interventions, aimed at enhancing adherence with antihypertensive medication. School of Pharmacy, Queen’s University Belfast, 97 Lisburn Road, Belfast BT9 7BL C. Lennon C. M. Hughes J. C. McElnay Department of Pharmacology and Therapeutics, Queen’s University Belfast, 97 Lisburn Road, Belfast BT9 7BL G. D. Johnston Int J Pharm Pract 2001:9(suppl):R8 References 1. Hamilton GA, Roberts SJ, Johnson JM, Tropp JR, Anthony-Odgren D, Johnson BF. Increasing adherence in patients with primary hypertension: an intervention. Health Values 1993;17( 1):3-11. 2. Bandura A. Self-efficacy: towards a unifying theory of behavioural change. Psycho1 Rev 1977;84:191-215. 3. Fishbein M, Ajzen I. Belief, attitude, intention, and behaviour: an introduction to theory and research. Reading MA: Addison-Wesley; 1975. 4. Ramsay LE, Williams B, Johnston GD, MacGregor GA, Poston L, Potter JF, Poulter NR, Russell G. Guidelines for management of hypertension: report of the third working party of the British Hypertension Society. J Hum Hypertens 1999;13:569-92. R8 THE INTERNATIONAL JOURNAL OF PHARMACY PRACTICE, SEPTEMBER 2001 Downloaded from https://academic.oup.com/ijpp/article/9/Supplement_1/8/6139070 by guest on 11 July 2023