Multimorbidity, Mortality, and Long-Term Physical Functioning in 3 Prospective Cohorts of Community-Dwelling Adults

Multimorbidity is prevalent, but its optimal quantification and associations with mortality rate and physical functioning in young through older adults are uncertain. We used data collected using the Short Form-36 in the Nurses' Health Study (enrollment started in 1976), Nurses' Health Study II (begun in 1989), and Health Professionals Follow-up Study (begun in 1986) to identify associations of a multimorbidity-weighted index (MWI) and common alternative indices with mortality and future physical functioning. We used Cox proportional hazard ratios to determine incident 10-year mortality and general linear models to obtain coefficients for the associations of MWI with 4- and 8-year physical functioning. At baseline, mean values for the 219,950 participants were 55.0 (standard deviation, 3.7) years for age; 3.8 (range, 0-51) for MWI; 2.7 (range, 0-23) for disease count, and 0.43 (range, 0-13) for Charlson Comorbidity Index (CCI). During follow-up, 23,709 deaths (10.8%) occurred. CCI, MWI, and disease count were 0 for 77%, 12%, and 19% of participants, respectively. When comparing persons in the highest quartiles with those in the lowest, the hazard ratios for mortality were 6.04 (95% confidence interval (CI): 6.00, 6.09; P for trend < 0.0001) for the MWI, 4.86 (95% CI: 4.81, 4.91; P for trend < 0.0001) for disease count, and 3.29 (95% CI: 3.26, 3.32; P for trend < 0.0001) for the CCI. For future physical functioning, MWI had the best model fit and explained the greatest variance. Multimorbidity has important associations with future physical functioning and mortality that are easily captured with a readily measured index.