The concept of multimorbidity, and its re-branding as Multiple Long-Term Conditions (MLTC), has emerged relatively recently in response to healthcare that has become ever more fragmented and focused on diseases in isolation. As a GP and researcher, I’m often asked how I use MLTC in clinical practice, and often struggle to articulate its utility. This usually stems from a misplaced attempt to find examples of where knowing a person ‘has’ MLTC improved their care. Instead, by considering it as a lens through which to view and challenge the modern disease-oriented paradigm in health, MLTC helps me to reorient myself towards person-centred care.

The modern origins of multimorbidity

The recent origins of the term multimorbidity are perhaps surprising, given that the phenomenon it describes (of two conditions co-occurring in the same person) has always existed. The related term co-morbidity first appeared in 1970, referring to conditions occurring in the context of a specific index condition. Multimorbidity followed soon after with the earliest published paper in 1974. Until the 1990s, its use was mostly in German-language primary care and geriatric medicine papers (using the term Multimorbidität) and it wasn’t until the 2000s that multimorbidity gained international recognition.

The rise of MLTC as a concept parallels the increasing fragmentation of healthcare, acting as a counterpoint to the increasing specialisation and subspecialisation of modern medicine. As Barbara Starfield observed in 2011: “The benefits to health from advances in medicine in the 20th century have led to a shift away from patients’ problems to disease processes…and with a demonstrated decline in focus on the person.”. The growth of MLTC research reflects not only an awareness that people can have more than one condition at the same time, but more importantly, a recognition that this phenomenon is fundamental to study.

The challenge of demonstrating clinical value

Despite a growing amount of research describing the burden and impact of MLTC, it can be hard to pinpoint its clinical utility. People often ask me how I use it in my clinical role. The reality is that I don’t – at least, not directly. The answer that people usually expect, and that I want to provide, is that identifying a person as having MLTC enables a diagnosis or intervention that wouldn’t have been possible otherwise. Trying to answer the question by thinking of a person ‘having’ MLTC, as they might have a condition such as arthritis or diabetes, gets me into difficulty, because I can never find examples of where this was helpful. Clinical decision-making is inherently condition-specific, whereas MLTC is hugely varied – depending on the conditions we include, most of the population can be defined as having MLTC. This means that any two people with MLTC may share none of the same risk factors, conditions or impact on their lives, limiting its direct clinical use.

One answer might be to find subtypes or phenotypes of MLTC that are more specific. Indeed, this was the focus of my PhD – to identify ‘clusters’ of diseases, and of people with similar diseases. Sometimes these can be helpful in practice: for example, knowing that diabetes, hypertension and chronic kidney disease often cluster together means that when I see one or two of these conditions, I am more likely to test for another. However, as found in my PhD, it is difficult to distinguish whether clusters represent real patient phenotypes versus features of the clustering algorithm. Furthermore, variability in disease patterns within populations is often too great to be able to neatly categorize people into an interpretable number of clusters. After three years of clustering in MLTC, I am less hopeful that clustering can provide the sort of solutions that I can directly implement in my clinical role.

MLTC as a lens

By considering MLTC more broadly, the practical relevance to me as a GP becomes clearer. For example, recognising that the care of people with MLTC is often fragmented across multiple specialist teams prompts me to try and address care integration during appointments with simple actions such as checking hospital letters for inconsistencies in medications or asking patients how they are managing with their hospital appointments. MLTC also frames my interpretation of clinical guidelines, recognising that single disease guidelines may be less applicable to a person with multiple other conditions. Reflecting on how MLTC shapes my clinical practice, it is not direct, but rather as a lens through which I view clinical interactions. This reminds me to focus on the uniqueness of each person, rather than their diseases and encourages more holistic care.

More powerfully, MLTC provides researchers, clinicians and patients with a shared vocabulary. Despite ongoing debate about which conditions should be included, as a community we broadly agree on what it means, the contexts in which we use it and why it is important. Its clinical value lies in its ability to shift our gaze from diseases to people. In this way, MLTC is a crucial concept to help us navigate and challenge the single-disease paradigm that dominates in modern medicine.

Find out more about Dr Thomas Beaney's research into clustering Multiple Long-Term Conditions on his project website.

First published: 11 March 2025

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