By Eng Sing Lee

Multimorbidity, defined as the co-occurrence of several chronic conditions in an individual [1, 2], is increasingly common. In 2018, the Academy of Medical Sciences has declared multimorbidity a priority in global health research as it has become a norm rather than an exception for an individual to have multimorbidity [3]. Multimorbidity is a growing public health challenge as it accounts for the highest expenditure in the healthcare system [4]. In addition, multimorbidity brings about many profound implications such as decreased quality of life, functional decline, and increased healthcare utilisation among many other negative outcomes.

However, many researchers define multimorbidity differently and many different instruments were used to measure multimorbidity. For this reason, we conducted a systematic a review on the instruments used for measuring the association of the level of multimorbidity and clinically important outcomes [5]. The main objective of the systematic review was to provide a list of instruments that are suitable for use in studies aiming to measure multimorbidity in association with or for prediction of a specific outcome in community-dwelling individuals. We also provided details of the requirements, strengths and limitations of these instruments, and the chosen outcomes.

In total, we found 33 unique instruments. The most commonly used instrument was ‘Disease Count’ and it was also the only instrument that was associated with the three essential outcomes from the core outcomes set of multimorbidity research (COSmm) [6], which are quality of life, mental health and mortality. Other instruments included weighted indices and case-mix or pharmaceutical-based instruments. We hope that by describing these instruments in detail, researchers would be able to choose a suitable instrument for their research in multimorbidity.

References

1. Fortin M, Stewart M, Poitras ME, et al. A systematic review of prevalence studies on multimorbidity: toward a more uniform methodology. Ann Fam Med 2012;10(2):142–51. doi: https://doi.org/10.1370/afm.1337 [published Online First: 2012/03/14]
2. WHO. The World Health Report 2008. Primary Care – Now more than ever. 2008.
3. Multimorbidity: a priority for global health research The Academy of Medical Sciences 2018
4. Huber M, Knottnerus JA, Green L, et al. How should we define health? BMJ 2011;343:d4163. doi: 10.1136/bmj.d4163
5. Lee ES, Koh HL, Ho EQ, et al. Systematic review on the instruments used for measuring the association of the level of multimorbidity and clinically important outcomes. BMJ Open 2021;11(5):e041219. doi: 10.1136/bmjopen-2020-041219
6. Smith SM, Wallace E, Salisbury C, et al. A Core Outcome Set for Multimorbidity Research (COSmm). Ann Fam Med 2018;16(2):132-38. doi: 10.1370/afm.2178