Magnetic resonance imaging white matter hyperintensities and brain volume in the prediction of mild cognitive impairment and dementia.
OBJECTIVE
To determine whether magnetic resonance imaging (MRI) white matter hyperintensities (WMH), whole-brain atrophy, and cardiovascular risk factors predict the development of cognitive decline and dementia.


METHODS
Subjects were recruited into this prospective cohort study and followed for incident cognitive decline for mean (SD) 6.0 (4.1) years. Magnetic resonance imaging dual-echo sequences, obtained at baseline, were used to determine the volume of WMH and the brain parenchymal fraction (BPF), the proportion of the intracranial cavity occupied by brain. White matter hyperintensity volume was analyzed as the percentage of intracranial volume (WMHr); "high WMH" was defined as a WMHr more than 1 SD above the mean.


METHODS
General community.


METHODS
Volunteer sample consisting of 67 subjects with normal cognition and 156 subjects with mild cognitive impairment (MCI).


METHODS
Time to diagnosis of MCI (among those with normal cognition at baseline) or time to diagnosis of dementia, either all-cause or probable Alzheimer disease (AD) (among those with MCI at baseline). Cox proportional hazards models were used for multivariable analysis.


RESULTS
High WMH was a predictor of progression from normal to MCI (adjusted hazard ratio [HR], 3.30; 95% confidence interval [CI], 1.33-8.17; P= .01) but not conversion from MCI to all-cause dementia. Conversely, BPF did not predict progression from normal to MCI but did predict conversion to dementia (adjusted HR, 1.10 for each 1% decrease in BPF; 95% CI, 1.02-1.19; P= .02). When conversion to AD dementia was considered as the outcome, BPF was likewise a predictor (adjusted HR, 1.16 for each 1% decrease in BPF; 95% CI, 1.08-1.24; P< .001), but high WMH was not. Past tobacco smoking was associated with both progression from normal to MCI (adjusted HR, 2.71; 95% CI, 1.12-6.55; P= .03) and conversion to all-cause dementia (adjusted HR, 2.08; 95% CI, 1.13-3.82; P= .02), but not AD dementia.


CONCLUSIONS
These findings suggest that WMH are associated with the risk of progressing from normal to MCI. In persons whose cognitive abilities are already impaired, BPF predicts the conversion to dementia.
Smith
Eric E
EE
Neurology Clinical Trials Unit, Department of Neurology, Massachusetts General Hospital, Boston, Massachusetts 02114, USA. eesmith@partners.org
Egorova
Svetlana
S
Blacker
Deborah
D
Killiany
Ronald J
RJ
Muzikansky
Alona
A
Dickerson
Bradford C
BC
Tanzi
Rudolph E
RE
Albert
Marilyn S
MS
Greenberg
Steven M
SM
Guttmann
Charles R G
CR
D000368:Aged; D000704:Analysis of Variance; D053327:Apolipoprotein E4 / Q000235:genetics; D001284:Atrophy; D001921:Brain / Q000473:pathology*; D002318:Cardiovascular Diseases / Q000453:epidemiology; D002561:Cerebrovascular Disorders / Q000473:pathology; D003072:Cognition Disorders / Q000235:genetics / Q000473:pathology*; D003704:Dementia / Q000235:genetics / Q000473:pathology*; D018450:Disease Progression; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009483:Neuropsychological Tests; D011379:Prognosis; D011446:Prospective Studies; D012044:Regression Analysis; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects
D053327:Apolipoprotein E4