Patients with a single illness who are taking many drugs have an increased risk of being admitted to hospital, but for patients with multiple conditions, taking many medicines is now associated with a near-normal risk of admission, according to new research findings.

“The commonly-held assumption that polypharmacy is always hazardous and represents poor care is misleading. Our work shows that we need more sophisticated approaches to assessing the appropriateness of each patient’s set of medicines,” says lead author Dr Rupert Payne, of the Cambridge Centre for Health Services research.

Reporting their findings in the British Journal of Clinical Pharmacology, the authors point out that polypharmacy is becoming increasingly common, partly because there are more elderly people now and also because of the increasing numbers of patients being diagnosed with multiple health conditions.

Working with colleagues in Nottingham and Glasgow, Dr Payne analysed Scottish NHS primary care data for 180,815 adults with long-term medical conditions. They identified the numbers of regular medications each person was taking and linked this to whether or not the person was admitted to hospital in the following year.

This work revealed that, for patients with only a single medical condition, taking 10 or more medications was associated with a more than three-fold increase in the chance of having an unplanned hospitalisation, compared to patients who took only one to three medications.

However, they also found that patients with six or more medical conditions who used 10 or more medications increased their chance of a hospital admission only 1.5 times compared to the group taking one to three medicines.

Discussing the study findings, Dr Payne says that they are highly relevant to the development and assessment of prescribing skills in general practice, where the majority of long-term clinical care is undertaken and where doctors often prescribe drugs for long periods of time.

“It is particularly important at times when doctors are caring for older patients and those with multiple medical conditions in whom multiple medications are often used,” he adds.

Dr Payne also says that previous studies have missed the different effect that polypharmacy has in different people because they have used “overly-simplistic” approaches when looking at the effect of taking many drugs at once.

The new study demonstrates the need for “more sophisticated and nuanced” approaches when measuring the impact of polypharmacy in future clinical research, he adds.