Sexual Dimorphism in Healthy Aging and Mild Cognitive Impairment: A DTI Study

Citation metadata

From: PLoS ONE(Vol. 7, Issue 7)
Publisher: Public Library of Science
Document Type: Article
Length: 9,424 words
Lexile Measure: 1540L

Document controls

Main content

Article Preview :

Author(s): Laurence O'Dwyer 1 , * , Franck Lamberton 2 , Arun L. W. Bokde 3 , Michael Ewers 4 , Yetunde O. Faluyi 5 , 6 , Colby Tanner 7 , Bernard Mazoyer 2 , 8 , 9 , Desmond O'Neill 10 , Máiréad Bartley 10 , Rónán Collins 10 , Tara Coughlan 10 , David Prvulovic 1 , Harald Hampel 1

Introduction

Many studies have found that the clinical symptoms of Alzheimer's disease (AD) are not tightly linked to brain pathology [1]-[4]. This is underlined by post mortem findings which indicate that up to 25% of individuals who fulfil the neuropathological criteria for AD dementia remain cognitively normal during their lifetime [4]. The degree to which pathology translates into clinical symptoms has been shown to be strongly dependent on sex with women more likely to express pathology as a diagnosis of AD dementia, whereas men are more resistant to clinical symptoms in the face of the same degree of pathology [3]. This may be partly related to differences in brain structure, including the fact that the absolute brain volume of women is less than that of men [5], [6]. A higher synaptic density, greater number of neurons and larger brain size might partly explain why men appear to have a greater buffer against pathology translating into clinical symptoms of AD [7], [8]. Larger brain size, greater synaptic density, as well as education and a cognitively demanding occupation, have been suggested to contribute to an increased brain reserve that results in more efficient cognitive networks that can delay the onset of clinical symptoms of dementia [1], [9]-[13]. Some studies suggest that larger brains are less likely to develop AD [10] but this has not always been supported [14].

While AD usually entails significant memory loss, an intermediate state between healthy ageing and AD, termed mild cognitive impairment (MCI) has become widely recognized and a significant proportion of those with MCI may represent a prodromal state of AD [15]. White matter (WM) tracts may be key indicators of early pathology as these tracts are uniquely vulnerable to damage [16] and studies have shown WM damage both in MCI [17]-[20] and AD [21]-[24]. MRI studies have also indicated WM volume loss in AD dementia [25], although GM loss appears to be more pronounced [26], [27].

Diffusion tensor imaging (DTI) offers a powerful tool for the investigation of WM in vivo [28]-[30] but to our knowledge no DTI studies have yet looked at differences in white matter integrity between men and women in MCI or AD dementia, despite the fact that age and sex are the two highest risk factors for AD dementia [31]-[35].

In addition to the scarcity of DTI studies examining sex differences in the WM of MCI and AD patients, there are also very few studies which have examined WM differences between healthy older men and women. Studies in younger cohorts have shown that men have higher FA than women in the corpus callosum [36]-[38]. Men have also been shown...

Source Citation

Source Citation   

Gale Document Number: GALE|A477114897