Macular Thickness as a Potential Biomarker of Mild Alzheimer's Disease

Although several postmortem findings in the retina of patients with Alzheimer's disease (AD) are available, new biomarkers for early diagnosis and follow-up of AD are still lacking. It has been postulated that the defects in the retinal nerve fiber layer (RNFL) may be the earliest sign of AD, even before damage to the hippocampal region that affects memory. This fact may reflect retinal neuronal-ganglion cell death and axonal loss in the optic nerve in addition to aging

Spatial analysis of thickness changes in ten retinal layers of Alzheimer’s disease patients based on optical coherence tomography

The retina is an attractive source of biomarkers since it shares many features with the brain. Thickness differences in 10 retinal layers between 19 patients with mild Alzheimer’s disease (AD) and a control group of 24 volunteers were investigated. Retinal layers were automatically segmented and their thickness at each scanned point was measured, corrected for tilt and spatially normalized. When the mean thickness of entire layers was compared between patients and controls, only the outer segment layer of patients showed statistically significant thinning. However, when the layers were compared point-by point, patients showed statistically significant thinning in irregular regions of total retina and nerve fiber, ganglion cell, inner plexiform, inner nuclear and outer segment layers. Our method, based on random field theory, provides a precise delimitation of regions where total retina and each of its layers show a statistically significant thinning in AD patients. All layers, except inner nuclear and outer segments, showed thickened regions. New analytic methods have shown that thinned regions are interspersed with thickened ones in all layers, except inner nuclear and outer segments. Across different layers we found a statistically significant trend of the thinned regions to overlap and of the thickened ones to avoid overlapping

Early dysfunction of functional connectivity in healthy elderly with subjective memory complaints

It is still an open question whether subjective memory complaints (SMC) can actually be considered to be clinically relevant predictors for the development of an objective memory impairment and even dementia. There is growing evidence that suggests that SMC are associated with an increased risk of dementia and with the presence of biological correlates of early Alzheimer's disease. In this paper, in order to shed some light on this issue, we try to discern whether subjects with SMC showed a different profile of functional connectivity compared with subjects with mild cognitive impairment (MCI) and healthy elderly subjects. In the present study, we compare the degree of synchronization of brain signals recorded with magnetoencephalography between three groups of subjects (56 in total): 19 with MCI, 12 with SMC and 25 healthy controls during a memory task. Synchronization likelihood, an index based on the theory of nonlinear dynamical systems, was used to measure functional connectivity. Briefly, results show that subjects with SMC have a very similar pattern of connectivity to control group, but on average, they present a lower synchronization value. These results could indicate that SMC are representing an initial stage with a hypo-synchronization (in comparison with the control group) where the brain system is still not compensating for the failing memory networks, but behaving as controls when compared with the MCI subjects

Cognitive reserve benefits brain efficiency in healthy aging

The concept of cognitive reserve (CR) describes the mind’s resistance to the progressive damage of the brain and probably this can be reflected as the ability to recruit brain networks in an effective way. It is as- sociated with the abilityto copewith the deleterious effects of brain damage,brain degeneration, or age-related changes on cognitive performance

Changes in visual function and retinal structure in the progression of Alzheimer's disease

Background: Alzheimer’s Disease (AD) can cause degeneration in the retina and optic nerve either directly, as a result of amyloid beta deposits, or secondarily, as a result of the degradation of the visual cortex. These effects raise the possibility that tracking ophthalmologic changes in the retina can be used to assess neurodegeneration in AD. This study aimed to detect retinal changes and associated functional changes in three groups of patients consisting of AD patients with mild disease, AD patients with moderate disease and healthy controls by using non-invasive psychophysical ophthalmological tests and optical coherence tomography (OCT). Methods: We included 39 patients with mild AD, 21 patients with moderate AD and 40 age-matched healthy controls. Both patients and controls were ophthalmologically healthy. Visual acuity, contrast sensitivity, colour perception, visual integration, and choroidal thicknesses were measured. In addition, OCT and OCT angiography (OCTA) were applied. Findings: Visual acuity, contrast sensitivity, colour perception, and visual integration were significantly lower in AD patients than in healthy controls. Compared to healthy controls, macular thinning in the central region was significant in the mild AD patients, while macular thickening in the central region was found in the moderate AD group. The analysis of macular layers revealed significant thinning of the retinal nerve fibre layer, the ganglion cell layer and the outer plexiform layer in AD patients relative to controls. Conversely, significant thickening was observed in the outer nuclear layer of the patients. However, mild AD was associated with significant thinning of the subfovea and the nasal and inferior sectors of the choroid. Significant superonasal and inferotemporal peripapillary thinning was observed in patients with moderate disease. Conclusions: The first changes in the mild AD patients appear in the psychophysical tests and in the central macula with a decrease in the central retinal thickness. When there was a disease progression to moderate AD, psychophysical tests remained stable with respect to the decrease in mild AD, but significant thinning in the peripapillary retina and thickening in the central retina appeared. The presence of AD is best indicated based on contrast sensitivity

El descenso de la capacidad antioxidante favorece el daño oxidativo a proteínas y ADN en demencia Alzheimer

Trabajo presentado en las XVII Jornadas de Nutrición Práctica y VIII Congreso Internacional de Nutrición, Alimentación y Dietética celebradas en Madrid (España) del 17 al 19 de abril de 2013

Efecto del ácido fólico y del agua sulfurada sobre la viabilidad celular inducida por homocisteína en pacientes con Alzheimer

Trabajo presentado en las XVII Jornadas de Nutrición Práctica y VIII Congreso Internacional de Nutrición, Alimentación y Dietética, celebradas en Madrid (España) del 17 al 19 de abril de 2013

Productos de glicación avanzada (AGEs), oxidación de proteínas y estatus antioxidante en pacientes con demencia Alzheimer

Trabajo presentado en el 55 Congreso de la Sociedad Española de Geriatría y Gerontología. 2º Congreso de la Sociedad Valenciana de Geriatría y Gerontología, celebrado en Valencia (España) del 12 al 14 de junio de 2013

Ophthalmologic Psychophysical Tests Support OCT Findings in Mild Alzheimer's Disease

Purpose. To analyze in mild Alzheimer's disease (MAD) patients, GDS-4 (Reisberg Scale), whether or not some psychophysical tests (PTs) support OCT macular findings in the same group of MAD patients reported previously. Methods. Twenty-three MAD patients and 28 age-matched control subjects with mean Mini Mental State Examination of 23.3 and 28.2, respectively, with no ocular disease or systemic disorders affecting vision were included. Best-corrected visual acuity (VA), contrast sensitivity (CS) (3, 6, 12, and 18 cpds), color perception (CP), and perception digital test (PDT) were tested in one eye of each patient. Results. In comparison with the controls, MAD patients presented (i) a significant decrease in VA, PDT, and CS for all spatial frequencies analyzed, especially the higher ones, and (ii) a significant increase in unspecific errors on the blue axis (P < 0.05 in all instances). In MAD patients, a wide a ROC curve was plotted in all PTs. Conclusions. In MAD, CS, VA, and the tritan axis in CP were impaired. The PTs with the greatest predictive value are the higher spatial frequencies in CS and tritan unspecific errors in CP. PT abnormalities are consistent with the structural findings reported in the same MAD patients using OCT

Analysis of Retinal Peripapillary Segmentation in Early Alzheimer’s Disease Patients

Decreased thickness of the retinal nerve fiber layer (RNFL) may reflect retinal neuronal-ganglion cell death. A decrease in the RNFL has been demonstrated in Alzheimer’s disease (AD) in addition to aging by optical coherence tomography (OCT). Twenty-three mild-AD patients and 28 age-matched control subjects with mean Mini-Mental State Examination 23.3 and 28.2, respectively, with no ocular disease or systemic disorders affecting vision, were considered for study. OCT peripapillary and macular segmentation thickness were examined in the right eye of each patient. Compared to controls, eyes of patients with mild-AD patients showed no statistical difference in peripapillary RNFL thickness (P>0.05); however, sectors 2, 3, 4, 8, 9, and 11 of the papilla showed thinning, while in sectors 1, 5, 6, 7, and 10 there was thickening. Total macular volume and RNFL thickness of the fovea in all four inner quadrants and in the outer temporal quadrants proved to be significantly decreased (P<0.01). Despite the fact that peripapillary RNFL thickness did not statistically differ in comparison to control eyes, the increase in peripapillary thickness in our mild-AD patients could correspond to an early neurodegeneration stage and may entail the existence of an inflammatory process that could lead to progressive peripapillary fiber damage