Increased rates of mortality and hospitalisation were associated with underuse of medicines in older patients, even when controlling for polypharmacy and misuse, according to the findings of a Belgian study.
There was an increased risk of mortality (hazard ratio [HR] 1.39; 95% confidence interval [CI] 1.10–1.76) and hospitalisation (HR 1.26; 95% CI 1.10–1.45) for each additional underused medicine, the study results show.
“Polypharmacy, underuse and misuse was highly prevalent in adults aged 80 years and older,” say the researchers, led by Maarten Wauters, PhD researcher at the Heymans Institute of Pharmacology, Ghent University, Belgium. “Surprisingly, underuse and not misuse had strong associations with mortality and hospitalisation.”
The researchers based their findings on an analysis of patient records for a cohort of 503 older people living in the community.
The average age was 84 years; 58% were prescribed five medicines or more daily for the treatment of chronic conditions. The researchers, who published their findings in the British Journal of Clinical Pharmacology
(online, 18 July 2016), applied the Screening Tool of Older People’s Prescriptions (STOPP) to the patient records to judge medicines misuse and the Screening Tool to Alert to Right Treatment (START) to determine underuse. Survival and hospitalisation rates were also recorded at 18 months.
Polypharmacy, underuse and misuse of medicines were coexistent in almost half of older patients living in the community.
Underuse of medicines was identified in 67% of patients and misuse in 56% of patients. In 17% of patients, no underuse or misuse was found. The most prevalent criterion for underuse was the absence of an ACE inhibitor in patients with systolic heart failure (26%) and the absence of antiplatelet therapy in patients with vascular disease (24%).
The researchers found that a higher number of prescribed medicines correlated with more misused medications (P<0.001) and underused medications (P<0.001). The mortality rate was 8.9% and the hospitalisation rate was 31.0%.
“Our main finding is that every additional underused medication was associated with a relative increase in mortality rate of 36%, and in hospitalisation rate of 26% after 18 months, independent of the number of medications taken, and of the number of misused medications,” the researchers write.
“[Our study] suggests that the underuse of medications, next to polypharmacy, is strongly associated with outcomes. An explanation could be the reluctance of general practitioners to prescribe additional medications in patients with a high multimorbidity and polypharmacy, or of a possible aversion of patients for new therapies.
“Another hypothesis could be that substandard prescribing in older adults is a physician trait, and an instrumental variable that leads to a combination of polypharmacy, underuse, misuse, and higher mortality/hospitalisation.”
The same patterns found in this study are likely to be found in the UK, says Sara Dilks, a pharmacist in the Exeter Cluster Pharmacy Service in Devon, which provides medicines optimisation support to older people living at home.
But she points out: “What is not addressed in the paper is the concordance of the patients to their prescribed medication during the study. Reviewing patient health records electronically does not correlate to the medicines a patient actually chooses to take on a daily basis.”
Dilks says that in the UK there is a role for primary care pharmacists and technicians working in GP practices or the community setting to offer a medicines review service to older patients living in the community.
“Pharmacists can optimise an individual patient’s medicines regime, advise them on the daily practicalities of taking their medicines, educate and counsel patients on appropriate use of their medication, and suggest use of compliance aids to improve a patient’s concordance,” she says.
 Wauters M, Elseviers M, Vaes B et al. Too many, too few, or too unsafe? Impact of inappropriate prescribing on mortality, and hospitalisation in a cohort of community-dwelling oldest old. British Journal of Clinical Pharmacology 2016. doi: 10.1111/bcp.13055