Measuring multimorbidity in research: a Delphi consensus study

Iris Ho, Amaya Azcoaga-Lorenzo, Ashley Akbari, Jim Davies, Kamlesh Khunti, Umesh Kadam, Ronan Lyons, Colin McCowan, Stewart Mercer, Krishnarajah Nirantharakumar, Sophie Staniszewska, Bruce Guthrie

Research output: Contribution to journalArticlepeer-review


Objective: To develop international consensus on the definition and measurement of multimorbidity in research.

Design and setting: Modified Delphi study with data collected in three online rounds from participants between 30/11/20 and 18/5/21.

Participants: Professionals interested in multimorbidity and people with long-term conditions were recruited to separate professional and public panels. 150 professional and 25 public participants completed the round-one survey. Round 2/3 response rates were 83%/92% for professionals, and 88%/93% in the public panel.

Results: There was consensus across both panels that multimorbidity should be defined as two or more long-term conditions. ‘Complex multimorbidity’ was perceived to be a useful concept, but there was no consensus on how to define it. There was consensus in both panels that conditions should be included in a multimorbidity measure if they were one or more of: (1) currently active; (2) permanent in their effects; (3) requiring current treatment, care or therapy; (4) requiring surveillance; or (5) relapsing/remitting conditions requiring ongoing care. Consensus was reached for 24 conditions to ‘always include’ in multimorbidity measures and 35 conditions to ‘usually include unless a good reason not to’. Simple counts were preferred for estimating prevalence and examining clustering/trajectories, and weighted measures were preferred for risk adjustment and outcome prediction.

Conclusions: Prior multimorbidity research is limited by inconsistent definitions and approaches to measuring multimorbidity. This Delphi study identifies professional and public panel consensus guidance to facilitate consistency of definition and measurement, and to improve study comparability and reproducibility.

Funding: Health Data Research UK (CFC0110)
Original languageEnglish
Article numbere000247
JournalBMJ Medicine
Issue number1
Publication statusPublished - 27 Jul 2022


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