title: Head circumference as a useful surrogate for intracranial volume in older adults.
abstract: BACKGROUND
  Intracranial volume (ICV) has been proposed as a measure of maximum lifetime brain size. Accurate ICV measures require neuroimaging which is not always feasible for epidemiologic investigations. We examined head circumference as a useful surrogate for ICV in older adults.
  
  
  METHODS
  99 older adults underwent Magnetic Resonance Imaging (MRI). ICV was measured by Statistical Parametric Mapping 8 (SPM8) software or Functional MRI of the Brain Software Library (FSL) extraction with manual editing, typically considered the gold standard. Head circumferences were determined using standardized tape measurement. We examined estimated correlation coefficients between head circumference and the two MRI-based ICV measurements.
  
  
  RESULTS
  Head circumference and ICV by SPM8 were moderately correlated (overall r = 0.73, men r = 0.67, women r = 0.63). Head circumference and ICV by FSL were also moderately correlated (overall r = 0.69, men r = 0.63, women r = 0.49).
  
  
  CONCLUSIONS
  Head circumference measurement was strongly correlated with MRI-derived ICV. Our study presents a simple method to approximate ICV among older patients, which may prove useful as a surrogate for cognitive reserve in large scale epidemiologic studies of cognitive outcomes. This study also suggests the stability of head circumference correlation with ICV throughout the lifespan.
authors.affiliation: Division of Aging,Brigham and Women's Hospital,Harvard Medical School,Boston,MA,USA.
authors.forename: Tammy T
authors.initials: TT
authors.lastname: Hshieh
authors.affiliation: Department of Radiology,Beth Israel Deaconess Medical Center,Harvard Medical School,Boston,MA,USA.
authors.forename: Meaghan L
authors.initials: ML
authors.lastname: Fox
authors.affiliation: Aging Brain Center,Institute for Aging Research,Hebrew SeniorLife,Boston,MA,USA.
authors.forename: Cyrus M
authors.initials: CM
authors.lastname: Kosar
authors.affiliation: Center for Neurological Imaging,Brigham and Women's Hospital,Harvard Medical School,Boston,MA,USA.
authors.forename: Michele
authors.identifier: http://orcid.org/0000-0003-1876-639X
authors.initials: M
authors.lastname: Cavallari
authors.affiliation: Department of Medicine,Beth Israel Deaconess Medical Center,Harvard Medical School,Boston,MA,USA.
authors.forename: Charles R G
authors.initials: CR
authors.lastname: Guttmann
authors.affiliation: Department of Radiology,Beth Israel Deaconess Medical Center,Harvard Medical School,Boston,MA,USA.
authors.forename: David
authors.identifier: http://orcid.org/0000-0002-8206-1995
authors.initials: D
authors.lastname: Alsop
authors.affiliation: Division of Aging,Brigham and Women's Hospital,Harvard Medical School,Boston,MA,USA.
authors.forename: Edward R
authors.initials: ER
authors.lastname: Marcantonio
authors.affiliation: Aging Brain Center,Institute for Aging Research,Hebrew SeniorLife,Boston,MA,USA.
authors.forename: Eva M
authors.initials: EM
authors.lastname: Schmitt
authors.affiliation: Aging Brain Center,Institute for Aging Research,Hebrew SeniorLife,Boston,MA,USA.
authors.forename: Richard N
authors.initials: RN
authors.lastname: Jones
authors.affiliation: Aging Brain Center,Institute for Aging Research,Hebrew SeniorLife,Boston,MA,USA.
authors.forename: Sharon K
authors.initials: SK
authors.lastname: Inouye
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001921:Brain / Q000473:pathology*; D002508:Cephalometry; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009929:Organ Size; D012886:Skull / Q000033:anatomy & histology*
keywords: biomarkers; elderly; head circumference; intracranial volume; magnetic resonance imaging; older adults