POLYPHARMACY AND INAPPROPRIATE PRESCRIBING IN ELDERLY HONG KONG CHINESE PATIENTS

To the Editor: Hong Kong is an aging city, with the population aged 65 and older projected to increase from 0.9 million (12.5% of population) in 2008 to 1.7 million (21.3% of population) in 2025.1 The economic burden for the care of older people in Hong Kong is substantial.2 Prescribing multiple medications in older patients is common,3, 4 with most treatment guidelines for chronic illnesses recommending combined drug regimens. Multiple drug use, or polypharmacy, in older adults increases the risks of inappropriate prescribing, adverse drug events, and hospitalization.3, 5 The objectives of this study were to evaluate the prevalence and predictors of polypharmacy and inappropriate drug use in geriatric patients in a Hong Kong ambulatory setting. A cross-sectional, retrospective, observational study was conducted in the outpatient settings of two hospitals in Hong Kong. Patients aged 65 and older attending medical general specialist outpatient clinics or medical geriatrics specialist outpatient clinics between January 2007 and December 2007 were identified, and 400 patients were randomly selected using computer-generated random numbers. Patient data were collected from patients' medical records, including demographics, comorbidities, and prescription drug use (for at least 7 days). Over-the-counter herbal medications and health supplements were not included in data collection because of incomplete documentation of those items. Outcome assessments included polypharmacy and potentially inappropriate medications (PIMs). Polypharmacy was defined as the concomitant use of five of more medications.6 The Beers drugs-to-avoid criteria (2003 update) were used to assess PIMs.7 Drugs were classified as inappropriate in two categories: those that generally should be avoided in older adults and those to be avoided in combination with specific comorbidities. Data analysis was performed using SPSS 11.0 for Windows (SPSS, Inc., Chicago, IL). Univariate analysis was first performed using the Pearson chi-square test and parametric Student t-test, where appropriate, to identify significant factors associated with polypharmacy and PIMs. The factors found to have significant correlation were further analyzed using forward stepwise multiple logistic regression models. P<.05 was considered statistically significant. The mean age ± standard deviation of the cohort was 77.2 ± 7.0; 173 (43.3%) were male. The mean number of comorbidities was 4.8 ± 2.5. The most common underlying diseases were hypertension (63.3%), diabetes mellitus (33.0%), and stroke (30.0%). The mean number of prescribed drugs per patient was 5.9 ± 3.1. Of 400 patients, 260 (65.0%) were receiving five or more prescription items, and 43 (10.8%) were taking 10 or more. One hundred twenty-one (30.3%) patients were taking at least one PIM listed in the Beers criteria (90 (22.5%) had 1 PIM; 26 (6.5%) had 2 PIMs; 5 (1.3%) had ≥3 PIMs). The most commonly prescribed PIMs from the list of drugs that generally should be avoided were propoxyhene in 28 patients (7.0%), methyldopa in 24 patients (6.0%), and first-generation antihistamines in 24 patients (6.0%). For a disease-specific list of the Beers criteria, the most common PIMs prescribed were calcium channel blockers in 16 patients with chronic constipation (4.0%) and pseudoephedrine in four patients with hypertension (1.0%). Univariate analysis showed that older patients; patients who were dependent in daily activities; residents of old-age home; and those with a greater number of comorbidities or a history of diabetes mellitus, hypertension, ischemic heart disease, depression, asthma, gout, osteoarthritis, renal impairment, gastrointestinal ulcers, and stroke were associated with polypharmacy. Multiple logistic regression analysis further identified depression, ischemic heart disease, diabetes mellitus, hypertension, patients with four or more disease states, and patients aged 70 and older were significantly associated with polypharmacy (Table 1). For predictors of PIMs, univariate analysis identified three factors (ischemic heart disease, asthma, and polypharmacy), and only polypharmacy was significantly associated with PIMs in the multiple logistic regression analysis (Table 1). The results of the current study showed an increase in the prevalence of polypharmacy in older Hong Kong adults from 32% more than a decade ago8 to 65%. It was consistent to the findings reported in the United States (68%).3 The comorbidities that had a significant association with polypharmacy (hypertension, ischemic heart disease, diabetes mellitus, and depression) were similar to the predictors reported in the literature.9 Approximately one-third of the present cohort received at least one PIM, and polypharmacy was found to be the single factor most associated with PIMs. The present study suggests that the prevalence of polypharmacy is high in older Hong Kong adults and that polypharmacy is associated with PIMs. The predictors of polypharmacy that were identified provide insights into the target high-risk patient groups of PIMs. This study was limited by the shortcoming of the Beers criteria that only drugs to be avoided were evaluated, whereas drugs that are essential for older adults were not assessed. Further studies should include the evaluation of indispensable drugs for older adults. Conflict of Interest: The editor in chief has reviewed the conflict of interest checklist provided by the authors and has determined that the authors have no financial or any other kind of personal conflicts with this paper. Author Contributions: Ms. Lam, Mr. Mak, and Ms. Chan: study design, data collection and analysis, interpretation of data, and preparation of manuscript. Ms. Yao and Mr. Leung: study design and supervision of the project at the two study sites. Prof. You: study design, interpretation of data, preparation of manuscript, and supervision of the study. Sponsor's Role: None.