Characteristics, service use and mortality of clusters of multimorbid patients in England: a population-based study
Authors: Zhu Yajing , Edwards Duncan , Mant Jonathan , Payne Rupert A , Kiddle Steven 
Published: June 2019

Background

Multimorbidity is one of the principal challenges facing health systems worldwide. To help understand the changes to services and policies that are required to deliver better care, we used a novel approach to investigate which diseases co-occur and how combinations are associated with mortality and service use.

Methods

Linked primary and secondary care electronic health records contributed by 382 general practices in England to the Clinical Practice Research Datalink (CPRD) were used. The study included a representative set of multimorbid adults (18 years old or more) with two or more long-term conditions (N=113,211). A random set of 80% of the multimorbid patients (N=90,571) were stratified by age and clustered using latent class analysis. Consistency between obtained disease profiles, classification quality and associations with demographic characteristics and primary outcomes (hospitalisation, polypharmacy and mortality) was validated in the remaining 20% of multimorbid patients (N=22,640).

Findings

We identified twenty patient clusters across four age strata. The clusters with the highest mortality comprised psychoactive substance and alcohol misuse (aged 18-64), coronary heart disease, depression and pain (aged 65-84) and coronary heart disease, heart failure and atrial fibrillation (aged 85+). The clusters with the highest service use coincided with those with highest mortality for people aged over 65. For people aged 18-64, the cluster with the highest service use comprised depression, anxiety and pain. The majority of 85+ year olds multimorbid patients belonged to the cluster with the lowest service use and mortality for that age range. Pain featured in thirteen clusters.

Interpretation

This work has highlighted patterns of multimorbidity that have implications for health services. These include the importance of psychoactive substance and alcohol misuse in people under the age of 65; of co-morbid depression and coronary heart disease in people aged 65-84, and of cardiovascular disease in people aged 85+.

Funding

UK Medical Research Council

Research in context

Evidence before this study

We searched PubMed using the keyword list “multimorbidity, co-morbidity, disease patterns, clusters, service use, long-term conditions, chronic conditions” for studies published in English. We also reviewed multiple systematic reviews of multimorbidity patterns, and the policy report of multimorbidity research issued by the Academy of Medical Sciences in 2018.

Most studies have focused on older populations (aged 60+) and often used a small list of long-term conditions. Multimorbidity clusters composed of more than two conditions have not been well profiled mostly due to non-representative and small samples. There is substantial heterogeneity in the number of conditions considered (often less than 20) and in the statistical methods. Most studies focused on grouping diseases rather than patients, making it less straightforward to relate patients to outcomes in order to facilitate patient-centred care.

Added value of this study

This study is the first to describe and validate clusters of multimorbid patients across the adult lifecourse using a patient-centred probabilistic clustering approach. This leads to a more nuanced understanding of the relationship between age, multimorbidity and mortality and new insights into the importance of different clusters. For example, contrary to perceived wisdom, we show that the majority of 85+ year old multimorbid patients belong to a cluster with relatively low service use and mortality for that age group. We identify a cluster of younger multimorbid patients with psychoactive substance misuse that have a mortality rate 18 times higher than their non-multimorbid peers.

Implications of all the available evidence

We have validated and added to the list of disease combinations where tailored approaches could be attempted to better manage multimorbid patients and develop effective interventions. For example, the high mortality of younger multimorbid patients with psychoactive substance misuse might be reduced by addressing risk factors (e.g. drug use, smoking, deprivation) which are amenable to intervention.