Association of a modified physiologic index with mortality and incident disability: The health, aging, and body composition study

Jason L. Sanders, Robert M. Boudreau, Brenda W. Penninx, Eleanor M. Simonsick, Stephen B. Kritchevsky, Suzanne Satterfield, Tamara B. Harris, Douglas C. Bauer, Anne B. Newman

Research output: Contribution to journalArticle

Abstract

Background.Indexes constructed from components may identify individuals who age well across systems. We studied the associations of a Modified Physiologic Index (systolic blood pressure, forced vital capacity, Digit Symbol Substitution Test score, serum cystatin-C, serum fasting glucose) with mortality and incident disability.Methods.Data are from the Health, Aging, and Body Composition study on 2,737 persons (51.2% women, 40.3% black) aged 70-79 years at baseline and followed on average 9.3 (2.9) years. Components were graded 0 (healthiest), 1 (middle), or 2 (unhealthiest) by tertile or clinical cutpoints and summed to calculate a continuous index score (range 0-10). We used multivariate Cox proportional hazards regression to calculate risk of death or disability and determined accuracy predicting death using the area under the curve.Results.Mortality was 19% greater per index unit (p <. 05). Those with highest index scores (scores 7-10) had 3.53-fold greater mortality than those with lowest scores (scores 0-2). The unadjusted index (c-statistic = 0.656, 95% CI 0.636-0.677, p <. 0001) predicted death better than age (c-statistic = 0.591, 95% CI 0.568-0.613, p <. 0001; for comparison, p <. 0001). The index attenuated the age association with mortality by 33%. A model including age and the index did not predict death better than the index alone (c-statistic = 0.671). Prediction was improved with the addition of other markers of health (c-statistic = 0.710, 95% CI 0.689-0.730). The index was associated with incident disability (adjusted hazard ratio per index unit = 1.04, 95% CI 1.01-1.07).Conclusions.A simple index of available physiologic measurements was associated with mortality and incident disability and may prove useful for identifying persons who age well across systems.

Original languageEnglish (US)
Pages (from-to)1439-1446
Number of pages8
JournalJournals of Gerontology - Series A Biological Sciences and Medical Sciences
Volume67
Issue number12
DOIs
StatePublished - Dec 1 2012

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Keywords

  • Aging
  • Disability
  • Index
  • Longevity
  • Mortality

ASJC Scopus subject areas

  • Aging
  • Geriatrics and Gerontology

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