Prevalence and determinants of potentially inappropriate medication use in Hong Kong older patients: a cross-sectional study

Objectives: To assess the prevalence of potentially inappropriate medication (PIM) use in Hong Kong older patients visiting general outpatient clinics (GOPCs) between 2006 and 2014 and to identify factors associated with PIM use among older adults visiting GOPCs in 2014.

Design: Cross-sectional study.

Setting: GOPC.

Participants: Two study samples were constructed including a total of 844 910 patients aged 65 and above from 2006 to 2014 and a cohort of 489 301 older patients in 2014.

Measurements: Two subsets of the 2015 American Geriatrics Society Beers criteria-PIMs independent of diagnosis and PIMs due to drug-disease interactions-were used to estimate the prevalence of PIM use over 12 months. PIMs that were not included in the Hospital Authority drug formulary or with any specific restriction or exception in terms of indication, dose or therapy duration were excluded. Characteristics of PIM users and non-PIM users visiting GOPCs in 2014 were compared. Independent associations between patient variables and PIM use were assessed by stepwise multivariable logistic regression analysis.

Results: The 12-month period prevalence of PIM use decreased from 55.56% (95% CI 55.39% to 55.72%) in 2006 to 47.51% (95% CI 47.37% to 47.65%) in 2014. In the multivariable regression analysis, the strongest factor associated with PIM use was the number of different drugs prescribed (adjusted OR, AOR 23.01, 95% CI 22.36 to 23.67). Being female (AOR 0.89, 95% CI 0.85 to 0.87 for males vs females) and having a greater number of GOPC visits (AOR 1.83, 95% CI 1.78 to 1.88) as well as more than six diagnoses (AOR 1.43, 95% CI 1.36 to 1.52) were associated with PIM use.

Conclusions: The overall prevalence of PIM use in older adults visiting GOPCs decreased from 2006 to 2014 in Hong Kong although the prevalence of PIM use was still high in 2014. Patients with female gender, a larger number of medications prescribed, more frequent visits to GOPCs, and more than six diagnoses were at higher risk for PIM use.