White matter lesions are highly prevalent in individuals with Alzheimer’s disease (AD). Although these lesions are presumed to be of vascular origin and linked to small vessel disease in older adults, little information exists about their relationship to markers of classical AD neurodegeneration. Thus, we examined the link between these white matter changes (WMC) segmented on T1-weighted MRI and imaging markers presumed to be altered due to primary AD neurodegenerative processes. Tissue microstructure of WMC was quantified using diffusion tensor imaging and the relationship of WMC properties and volume to neuroimaging markers was examined in 219 cognitively healthy older adults and individuals with mild cognitive impairment and AD using data from the Alzheimer’s Disease Neuroimaging Initiative. No significant group differences in WMC properties were found. However, there were strong associations between diffusivity of WMC and ventricular volume, volume of WMC and total WM volume. In comparison, group differences in parahippocampal white matter microstructure were found for all diffusion metrics and were largely explained by hippocampal volume. Factor analysis on neuroimaging markers suggested two independent sets of covarying degenerative changes, with potentially age- and vascular-mediated tissue damage contributing to one factor and classical neurodegenerative changes associated with AD contributing to a second factor. These data demonstrate two potentially distinct classes of degenerative change in AD, with one factor strongly linked to aging, ventricular expansion, and both volume and tissue properties of white matter lesions, while the other factor related to classical patterns of cortical and hippocampal neurodegeneration in AD.
Pre-exposure prophylaxis (PrEP) has altered the public health landscape for gay, bisexual, and other men who have sex with men (GBM) by significantly increasing protection against HIV infection. Early epidemiologic data showed GBM generally used PrEP as prescribed, i.e., as an additional protective tool over and above barrier protection, although subsequent reports have been equivocal. Irrespective of population-level trends, some GBM appear to have reevaluated their HIV risk tolerance and changed their interactions with sex partners. Scant published data have focused on factors that influence PrEP-using GBM's decisions about sexual behavior-including condom use as well as sex with HIV-positive partners-and sexual communication practices. Thus, in this study, we investigated those research concerns qualitatively via content analysis of individual interviews conducted with 103 GBM in New York City (M age 32.5 years, 50% White, 64% on PrEP > 6 months). Emergent themes reflect (1) participants' strong HIV knowledge; (2) changing GBM community norms about condom use on PrEP; (3) increased focus on risk tolerance with individual differences in post-PrEP condom use; (4) appreciation for routine sexually transmitted infection (STI) screening in PrEP care concomitant with some STI knowledge deficits; (5) decreased stigma concerning, and greater comfort with, HIVpositive sex partners; and (6) increased confidence discussing HIV status and condom use preferences with partners. Findings have implications for future research as well as for clinical practice, such as enhanced STI education and provider-initiated discussions about risk compensation, serosorting, and sexual communication skills.
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