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J Gerontol A Biol Sci Med Sci. 2018 Jan 16;73(2):225-232. doi: 10.1093/gerona/glx114.

Multimorbidity and Physical and Cognitive Function: Performance of a New Multimorbidity-Weighted Index.

Author information

Division of General Medicine, University of Michigan.
Institute for Healthcare Policy and Innovation, University of Michigan, Ann Arbor.
Center for Clinical Management Research, Department of Veterans Affairs, Ann Arbor, Michigan.
Institute for Social Research, University of Michigan, Ann Arbor.
Division of General Medicine and Primary Care, Beth Israel Deaconess Medical Center and Harvard Medical School, Brookline, Massachusetts.



Multimorbidity is an important health outcome but is difficult to quantify. We recently developed a multimorbidity-weighted index (MWI) and herein assess its performance in an independent nationally-representative cohort.


Health and Retirement Study (HRS) participants completed an interview on physician-diagnosed chronic conditions and physical functioning. We determined the relationship of chronic conditions on physical functioning and validated these weights with the original, independently-derived MWI. We then determined the association between MWI with physical functioning, grip strength, gait speed, basic and instrumental activities of daily living (ADL/IADL) limitations, and the modified Telephone Interview for Cognitive Status (TICS-m) in adjusted models.


Among 20,509 adults, associations between chronic conditions and physical functioning varied several-fold. MWI values based on weightings in the HRS and original cohorts correlated strongly (Pearson's r = .92) and had high classification agreement (κ statistic = .80, p < .0001). Participants in the highest versus lowest MWI quartiles had weaker grip strength (-2.91 kg, 95% confidence interval [CI]: -3.51, -2.30), slower gait speed (-0.29 m/s, 95% CI: -0.35, -0.23), more ADL (0.79, 95% CI: 0.71, 0.87) and IADL (0.49, 95% CI: 0.44, 0.55) limitations, and lower TICS-m (-0.59, 95% CI: -0.77, -0.41) (all p < .001). We observed monotonic graded relationships for all outcomes with increasing MWI quartiles.


A multimorbidity index weighted to physical functioning performed nearly identically in a nationally-representative cohort as it did in its development cohorts, confirming broad generalizability. MWI was strongly associated with subjective and objective physical and cognitive performance. Thus, MWI serves as a valid patient-centered measure of multimorbidity, an important construct in research and clinical practice.


Chronic disease; Comorbidity; Disability; Multiple chronic conditions; Physical performance

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