Chronic Diseases and Physical Functioning: Development and Validation of an ICD-coded Multimorbidity Index

Melissa Y. Wei
Adjunct Assistant Professor, Department of Internal Medicine, Medical School


This pilot study uses patient-reported outcomes in the nationally-representative Health and Retirement Study and Medicare claims to develop and internally validate a multimorbidity index for International Classification of Diseases (ICD)-coded chronic conditions weighted to physical functioning. The study will yield a validated multimorbidity measure that captures the impact of coexisting chronic diseases on physical functioning in aging adults relevant for clinical care, research, and policy.


  • Wei MY, Luster JE, Ratz D, Mukamal KJ, Langa KM. Development, Validation, and Performance of a New Physical Functioning-Weighted Multimorbidity Index for Use in Administrative Data. J Gen Intern Med. 2021 Jan 19. doi: 10.1007/s11606-020-06486-7. Epub ahead of print. PMID: 33469748.
  • Wei MY, Luster JE, Chan CL, Min L. Comprehensive review of ICD-9 code accuracies to measure multimorbidity in administrative data. BMC Health Serv Res. 2020;20(1):489. Published 2020 Jun 1. doi:10.1186/s12913-020-05207-4
  • Wei MY, Ratz D, Mukamal KJ. Multimorbidity in Medicare Beneficiaries: Performance of an ICD-Coded Multimorbidity-Weighted Index. J Am Geriatr Soc. 2020 May;68(5):999-1006. doi: 10.1111/jgs.16310. Epub 2020 Jan 9. PMID: 31917465; PMCID: PMC7234913.
  • Wei MY, Luster J, Ratz D, Langa KM. Chronic conditions and physical functioning: development of a new ICD-coded multimorbidity index. Society of General Internal Medicine Annual Meeting. Washington, D.C. May 8, 2019.
  • Wei MY, Ratz D, Mukamal KJ. Multimorbidity and mortality among Medicare beneficiaries: simple disease count, Elixhauser, and a new ICD-coded multimorbidity-weighted index for use in claims data. American Geriatrics Society Annual Meeting. Portland, OR. May 3-5, 2019 (Presidential Poster Session).
  • Wei MY, Ratz D, Mukamal KJ. Multimorbidity in Medicare beneficiaries: Performance of an ICD-coded multimorbidity-weighted index. Multiple Chronic Conditions Scholars Workshop/Claude D. Pepper Older Americans Independence Centers Annual Meeting. Arlington, VA. April 24, 2019.
  • Wei, M. 2019. Chronic diseases and physical functioning: Development and validation of an ICD-coded multimorbidity index. 2nd annual MiCDA Pilot Project Symposium. March 28, 2019, Ann Arbor, MI.
  • Dr. Wei’s self-reported Multimordibity Weighted Index (MWI) is currently available for use on ( and was featured on GeriPal (