title: From Noise to Signal: The Age and Social Patterning of Intra-Individual Variability in Late-Life Health.
abstract: OBJECTIVE
  Despite a long tradition of attending to issues of intra-individual variability in the gerontological literature, large-scale panel studies on late-life health disparities have primarily relied on average health trajectories, relegating intra-individual variability over time to random error terms, or "noise." This article reintegrates the systematic study of intra-individual variability back into standard growth curve modeling and investigates the age and social patterning of intra-individual variability in health trajectories.
  
  
  METHODS
  Using panel data from the Health and Retirement Study, we estimate multilevel growth curves of functional limitations and cognitive impairment and examine whether intra-individual variability in these two health outcomes varies by age, gender, race/ethnicity, and socioeconomic status, using level-1 residuals extracted from the adjusted growth curve models.
  
  
  RESULTS
  For both outcomes, intra-individual variability increases with age. Racial/ethnic minorities and individuals with lower socioeconomic status tend to have greater intra-individual variability in health. Relying exclusively on average health trajectories may have masked important "signals" of life course health inequality.
  
  
  CONCLUSIONS
  The findings contribute to scientific understanding of the source of heterogeneity in late-life health and highlight the need to further investigate specific life course mechanisms that generate the social patterning of intra-individual variability in health status.
authors: National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland. lin.jielu@nih.gov.
authors: Jielu
authors: J
authors: Lin
authors: Department of Sociology, Case Western Reserve University, Cleveland, Ohio.
authors: Jessica A
authors: JA
authors: Kelley-Moore
mesh_terms: D000203:Activities of Daily Living / Q000145:classification; D000368:Aged; D000066492:Cognitive Aging; D060825:Cognitive Dysfunction / Q000175:diagnosis / Q000523:psychology; D004185:Disability Evaluation; D005260:Female; D015438:Health Behavior; D054624:Health Status Disparities; D006801:Humans; D007206:Individuality; D008297:Male; D008875:Middle Aged; D008913:Minority Groups; D015233:Models, Statistical; D055361:Multilevel Analysis; D012016:Reference Values; D012727:Sex Characteristics; D012737:Sex Factors; D012959:Socioeconomic Factors
keywords: Health disparities; Intra-individual variability; Multilevel growth curves; Residuals