Why personalised medicine is key for older adults

What is personalised medicine?

Ostensibly, personalised medicine is the way of tailoring a treatment to a particular patient and their needs. It’s a broad term, used to describe methods as varied as offering medicines to patients based on their genetic profile, to weighing the pros and cons of prescribing drugs based on patient priorities and the risk versus benefits.

Dr Stevenson's research focuses on taking a personalised approach to the optimisation of medicines in older adults. A key aspect of this us understanding the patient’s broader goals.

For example, somebody may want to be pain free so they can visit their family or friends, or perhaps have the agency so they can walk by themselves to the local shops. Understanding these goals can help inform whether to prescribe a new drug or not.

Another consideration is how the new medicine fits in with other medicines they are prescribed, as well as their broader lifestyle and values. There could be drug-food interactions, the dosing frequency might jar with their schedule, they could impact someone’s mobility and stamina, clash with religious practices, have cultural stigma attached. And this is just scratching the surface.

Why is it so important in older people?

There’s heterogeneity in older people – in other words, the older we become, the more different we become. This could be due to diseases we’ve accrued, our environment or our socioeconomic status. These factors impact the way we age resulting in a variation in physiological reserve and function, and our ability to cope with acute stressors. For example, starting a new medicine may be an acute stressor. In one older person with adequate reserve this may not cause any problems, while in another with reduced reserve this may result in an adverse health outcome.

The balance between risk and benefit becomes increasingly delicate as reserves decline or frailty increases. Considering the variation found in older people, the potential for increased vulnerability, and a high likelihood of them taking multiple medicines to treat multiple conditions, personalised medicine is all the more important to ensure that only medicines where the benefits outweigh the risks are prescribed. However, this risk benefit balance can be difficult to determine, in particular where life expectancy is limited and medicines are prescribed for disease prevention or slowing the progression of a condition.  

A biopsychosocial risk prediction model

As part of her research, Dr Stevenson’s set out to build a risk prediction model that would indicate which older adults would be most likely to experience harm from their medicines eight weeks after an acute hospital admission. The aim is to stratify patients into different risk categories so that those who are at highest risk are placed into a priority pathway to see a specialist, such as a geriatrician, senior pharmacist or clinical nurse specialist. Those who are at medium risk could be streamlined to see their GP, and those at a lower risk could potentially be followed up by a community pharmacist.

“I saw that clinical factors, such as patient’s diseases, their biochemistry – renal function, liver function, biomarkers – the types and numbers of medicine they were prescribed, had been looked at quite extensively and been included in previous models. But those models had limited accuracy. This reflected what I see in my clinical practice, where patients with multiple clinical conditions, take multiple medicines but they don’t all experience harm, so it seemed something was missing from the models.” 

After going through the literature it became evident that social variables were also key. Taking inspiration from the concept of frailty, where a wide range of factors are considered to understand someone’s risk of harm from external stressors, Dr Stevenson began building her model.

“How do they use their medicine? Do they have any support? What’s their mood like? Do they have motivation to take their medicine? Whether or not someone lived alone emerged as a key element.”

Another consideration is working out what’s really important to an older adult. Is it living to 100, or is it actually to have a better quality of life?

“Some research says that for older adults with advancing frailty, living for a long time is less of a priority than having a good quality of life.”

How genetics play a role

Clinicians and scientists have long recognised that people have variations in their genetic makeup that influences how well a drug works, but it is only recently that tests have begun to emerge that demonstrate this.

"We often prescribe a drug called clopidogrel to help patients after they’ve had a stroke. However, in some patients it doesn’t have any effect."

The exciting new frontier of genetic testing can hopefully be used in the future to inform clinical decision-making, contributing to prescribers’ own risk-benefit algorithms that exists in their heads, as well as the computer-based algorithms that are increasingly embedded in electronic patient record systems.