Abstract
Background:
Alzheimer’s disease (AD) is a debilitating condition that is widely known to adversely affect gray matter (GM) and white matter (WM) tracts within the brain. Recently, precision medicine has shown promise in alleviating the clinical and gross morphological trajectories of patients with AD. However, regional morphological changes have not yet been adequately characterized.
Objective:
Investigate regional morphological responses to a precision medicine-guided intervention with regards to white and gray matter in AD and mild cognitive impairment (MCI).
Methods:
Clinical and neuroimaging data were compiled over a 9-month period from 25 individuals who were diagnosed with AD or MCI receiving individualized treatment plans. Structural T1-weighted MRI scans underwent segmentation and volumetric quantifications via Neuroreader. Longitudinal changes were calculated via annualized percent change of WM or GM ratios.
Results:
Montreal Cognitive Assessment scores (p < 0.001) and various domains of the Computerized Neurocognitive Screening Vital Signs significantly improved from baseline to 9-month follow-up. There was regional variability in WM and GM atrophy or hypertrophy, but none of these observed changes were statistically significant after correction for multiple comparisons.
INTRODUCTION
Alzheimer’s disease (AD) is a debilitating condition that represents a spectrum of neurocognitive statuses ranging from mild cognitive impairment (MCI) to end-stage dementia [1]. Genetic factors that contribute to the development of AD include the presence of apolipoprotein E genes and methylenetetrahydrofolate reductase gene polymorphisms [2, 3]. There are also environmental factors in the development of AD, including cerebrovascular disease, traumatic brain injury, and cognitive activity [4]. Prevalent comorbidities such as diabetes, cardiovascular disease, and depression have also been associated with AD progression, potentially due to neuroinflammatory processes [5]. Novel efforts at curbing the progression of AD primarily revolve around disease-modifying therapies targeting well-known AD biomarkers such as amyloid-β and tau [6, 7]. Another well-explored interventional method to stem AD progression is the implementation of various lifestyle changes, including, but not limited to, diet, exercise, and nutritional supplementation [8–10].
Recently, precision medicine has surfaced as a promising approach to preventing progression of AD, consisting of a multidisciplinary approach focusing on various lifestyle factors of individuals in addition to addressing their comorbidities [4]. A pilot study implementing this individualized approach demonstrated cognitive improvements in neuropsychological tests as well as decreased gross rates of brain atrophy [11]. However, detailed morphological trends, including those at the regional and subcortical levels, have not yet been investigated with regards to outcomes of precision medicine in AD. AD is well-described with regards to gray matter (GM) changes, but white matter (WM) density and integrity are measures of interest as demyelination may manifest in earlier stages of AD [12]. Well-known regions of WM damage in AD are localized to frontal, temporal, and parietal lobes, areas that functionally correspond to the clinical syndromes of AD [13, 14]. Though the mechanisms of these morphological changes are not currently well-understood, previous studies hypothesize that WM damage may occur in a multitude of pathways, including secondary to Wallerian degeneration, or independently of gray matter changes via retrogenesis [15–17]. Thus, investigating WM changes may provide a deeper perspective into the therapeutic processes of precision medicine-guided interventions in AD.
This study aims to elucidate a more detailed insight into the morphological trends in the brain in response to precision medicine-based intervention, particularly with regards to WM changes and their localization. We hypothesize that paralleling the gross morphological trends that was observed in the previous study, WM changes in the cohort will be more reflective of normal aging patterns than traditional AD trajectories.
METHODS
Participants and evaluation
25 individuals who were diagnosed with AD or MCI from three clinical sites, Walnut Creek, California; San Rafael, California; and Ashland, Oregon, were selected for the 4 Winds Precision Medicine approach to Alzheimer’s Disease trial [11]. Each participant underwent treatment on an individualized basis consisting of diet, exercise, sleep hygiene, stress management, and supplements. If applicable, participants underwent treatment of comorbid infectious or toxic etiologies associated with cognitive decline or systemic inflammation, as well as correction of hormonal and endocrine deficiencies. Though detailed treatment protocol for each condition is more thoroughly explained in the pilot study, interventions of note included continuous positive airway pressure for participants with sleep apnea or upper airway resistance syndrome, valacyclovir for 2-6 months for those with evidence of Herpes simplex infection, and herbal remedies for those with active Epstein-Barr Virus or tick-borne infections [11].
Neuropsychological screening data was characterized with a combination of tools including Montreal Cognitive Assessment (MoCA) and Alzheimer’s Questionnaire (AQ-21), as well as Computerized Neurocognitive Screening Vital Signs (CNS-VS), a neurocognitive test battery represented by standardized scores with a mean of 100 and a standard deviation of 15. The CNS-VS were categorized into domains consisting of memory, verbal memory, visual memory, psychomotor speed, reaction time, processing speed, executive functioning, simple attention, and motor speed. Participants’ cognitive status was categorized based on AQ-21 scores, with previous validation of this tool demonstrating that those with scores 5 to 14 typically had MCI, whereas scores greater than 14 were associated with dementia [18]. With this stratification, 22 participants were diagnosed as having MCI and 3 were diagnosed as having dementia. Detailed protocols of participant selection and characterization, including inclusion and exclusion criteria, are described further in the prior publication [11]. In short, from a medical standpoint, exclusion criteria consisted of major health conditions such as seizures, cardiovascular disease, cancer, major psychiatric diagnosis, history of deep vein thrombosis, stroke, and diagnosis of a neurodegenerative disease other than AD (e.g., frontotemporal dementia). Concerns of practice effects were addressed by administering different MoCA tests at baseline, 3-month, 6-month, and 9-month evaluations and implementing the CNS-VS, which has been experimentally proven to minimize such effects [19].
Imaging
Each participant underwent magnetic resonance imaging (MRI) of the brain at baseline and after 9 months, upon completion of the treatment protocol. All scans were retrieved via 3-Tesla MRI scanners with either magnetization-prepared rapid acquisition gradient echo or spoiled gradient-recalled echo sequences. Each scan underwent segmentation and volumetric quantifications via Neuroreader, v2.7.0 [20]. In summary, the pipeline utilizes multi-atlas segmentation through non-linear registration and the resulting segmentations are run through multiple layers of corrections. Hippocampal segmentation was similarly achieved with a multi-atlas approach and probability maps were created with multiple templates to account for anatomic variabilities. Furthermore, in the novel version of the pipeline, lobar regions were further segmented into GM and WM volumes.
Statistical analyses
Volumetric change between baseline and follow-up were quantified via annualized percent change. Each volumetric measurement was corrected by the individual’s mean total intracranial volume and normalized into a percentage ratio. Paired t-tests were performed with raw annualized change rates of brain matter volumes to determine significance between baseline and 9-month follow-up at a significance level of 0.05. Wilcoxon sign-rank tests were utilized to compare overall MoCA scores and subscores between baseline and 9-month follow-up. All statistical analyses were performed with SPSS, Version 26. Corrections for multiple comparisons were performed using the Benjamini-Hochberg procedure at a false discovery rate of 0.05 [21].
RESULTS
Neuropsychological testing
A summary of demographics and neuropsychological testing results is listed in Table 1. MoCA scores (p < 0.001) and memory (p = 0.023), verbal memory (p = 0.006), psychomotor speed (p = 0.001), reaction time (p = 0.009), executive functioning (p < 0.001), simple attention (p = 0.023), and motor speed (p < 0.001) domains of the CNS-VS significantly improved from baseline to 9-month follow-up. Visual memory (p = 0.939) and processing speed (p = 0.166) domains of the CNS-VS did not significantly differ between the two time points.
Demographic and neuropsychological information
Demographic and neuropsychological information
MoCA, Montreal Cognitive Assessment (max score = 30); CNS-VS, Computerized Neurocognitive Assessment Vital Signs (standardized scores with mean = 100 and standard deviation = 15); 9mo, 9 months; Sig, significance.
White matter volume changes
A comprehensive list of WM volume changes is listed in Table 2. Cerebral WM volume decreased at a rate of 1.467% /year. Reductions were most pronounced in the frontal lobe regions (left: -1.393% /year; right: -4.995% /year), while increased WM volumes were most observed in the occipital (left: 0.304% /year; right: 2.104% /year) and parietal lobes (left: 1.952% /year, right: 0.611% /year). None of the regional WM volume changes were statistically significant after correction for multiple comparisons.
Cross-sectional and longitudinal data of White Matter Volume/mTIV ratios
mTIV, mean total intracranial volume; 9mo, 9 months.
A comprehensive list of GM volume changes is listed in Table 3. Cerebral GM volume decreased at a rate of 0.064% /year. Reductions were most pronounced in the right occipital (-5.92% /year) and parietal (left: -3.138% /year, right: -3.631% /year) regions, while increased GM volumes were most prominently observed in the right frontal (4.548% /year) and left temporal (1.972% /year) regions, though raw changes were less pronounced. None of the regional GM volume changes were statistically significant after correction for multiple comparisons.
Cross-sectional and longitudinal data of Gray Matter Volume/mTIV ratios
mTIV, mean total intracranial volume; 9mo, 9 months.
DISCUSSION
Previous studies show structural WM reductions of 0.5% -1% /year in normal aging, in a diffusively homogeneous pattern [22]. Precise annualized rates of WM reductions in AD are not well-elucidated in previous literature, but most significantly affected regions include bilateral medial temporal lobes [23]. In this study, many regions, along with overall WM volume, endured a change closer to those in normal aging trajectories than in AD, supporting our initial hypothesis. Furthermore, though not statistically significant, there were measurable increases in WM volumes in certain areas, especially the occipital lobe, which may be attributed to the tendency that AD preferentially affects the WM of frontal, parietal, and temporal regions [13, 14]. These findings are also accompanied by improved neuropsychological screening testing results in multiple domains of the CNS-VS, which have been corroborated in the pilot study [11]. Additionally, these differential increases may be attributed to compensatory reallocation of cognitive resources to different brain regions, as suggested by previous fMRI and connectome studies [24, 25].
GM atrophy rates generally range from 0.5-1% /year in normal aging, and 1-4% /year in AD, in areas congruous to WM atrophy [26, 27]. Regional improvements in GM localized around areas of AD-specific regions, particularly the frontal and temporal lobes, though there was noticeable variability between hemispheres. Although the mechanisms behind the observed regional variances in GM atrophy are unclear at this point, given that occipital lobe atrophy is not known to be associated with AD pathology, and both GM and WM volumes within AD-specific regions (frontal, parietal, temporal lobes) did not significantly decrease, a precision-medicine guided approach may align morphological changes to correspond more closely with normal aging than AD [28]. Further neurobiological studies should be pursued to investigate in detail the mechanisms behind the regional effects of a combined therapeutic approach.
Interestingly, the WM and GM changes exhibited some apparent decoupling, particularly in the occipital, frontal, and temporal lobes. Regions that had greater gray matter reductions tended to exhibit greater white matter increases, and vice versa. In individuals with AD, cortical damage and WM degeneration are spatially correlated [27]. This study suggests that precision medicine-based intervention may contribute in breaking down this relationship, as such associations are inconclusive in normal aging or even MCI [29, 30]. Thus, a precision medicine-based approach may curtail the pathophysiological processes driving the congruent reductions of WM and GM in AD, such as rarefaction of myelin, axonal gliosis, and Wallerian degeneration [29]. However, the precise mechanism of the apparent quantitative inverse relationship between WM and GM changes remains uncertain, and future studies should explore this potential phenomenon.
There exist limitations within our study, many of which are shared with the pilot study [11]. Though the study benefits from being longitudinal in nature, the small sample size of 25 individuals rendered statistical analyses to be less powerful than desired, and initially statistically significant results were marred by correction of multiple comparisons. Additionally, the cognitive screening tools and their respective boundaries utilized in this study have limited validity and reliability in diagnosing disease presence and severity compared to standardized, multi-hour, comprehensive neuropsychological evaluations. Particularly, though statistically significant, the observed neuropsychological testing score improvements may be partly attributed to ceiling effects, natural variability, and regression to the mean. Therefore, these observed raw score improvements of the MoCA scores and the CNS-VS may not necessarily translate to clinically significant outcomes, and should be further explored by employing a more comprehensive evaluation of objective and subjective findings. Another limitation was that imaging was only obtained at baseline and the 9-month follow-up period, which combined with its small timeframe relative to the chronic course of AD, limits generalization of the temporality of the study’s results. This limitation may have also played a factor in the high variability of regional differences observed in atrophy or hypertrophy rates. Furthermore, the nature of the calculation of annualized differences, given the relatively small volume ratios of some of the regions, may have over or underestimated the precise magnitude of such changes. Finally, the lack of a control group limits assessment of the relative efficacy of this intervention compared to other established treatment modalities.
Despite limitations, when considering the imaging results with observed functional and cognitive improvements, precision medicine-based interventions carry potential in addressing the neurodegenerative processes of AD. It is already known that generalized lifestyle changes, such as physical activity, mental activity, and adherence to a Mediterranean-based diet reduces brain atrophy rates in various AD-susceptible regions [31–33]. Such lifestyle changes, as well as addressing hormonal deficiencies and infections, have also been shown to reverse age-related brain volume losses and decrease the risk of AD progression [34, 35]. Moreover, comorbidities such as type II diabetes, metabolic syndrome, and obstructive sleep apnea have been shown to either contribute to neurodegenerative processes of AD or share the same pathophysiological mechanisms as AD, demonstrating a potential for this precision medicine-guided intervention to actively treat AD pathology [5, 37]. Thus, combining an individualized medical plan with generalized lifestyle recommendations may be an important step to improve both clinical and morphological outcomes of AD. Future innovations of therapy should be targeted in generating consistent levels of neurogenesis that correlate with significant increases in volumes and cognitive status.
AD is one of the most chronically debilitating diseases that commonly affect individuals with advancing age and is a condition that does not have a reliable form of treatment. However, pilot studies have established a precision medicine-based intervention as a promising approach to curtailing the pathophysiological processes in AD, both clinically and morphologically. This study validates that with the precision medicine intervention used in this pilot trial, there was no significant brain atrophy with regards to WM or GM in this cohort, though there are subtle regional variabilities that additional studies should further investigate across a longer time period. These findings support the potential efficacy of an individualized approach to the treatment of AD and may align individuals with AD to a clinical and morphological trajectory more fitting of normal aging.
Footnotes
ACKNOWLEDGMENTS
Outside contributions remain unchanged from the pilot study. We acknowledge the Four Winds Foundation, Diana Merriam, and Gayle Brown for their support of this study. We are grateful to David Perlmutter for introductions and CNS Vital Signs, Posit Science, HeartMath, Great Plains Laboratory, Cyrex Laboratory, Armin Labs, Bio-Botanical Research, Genova Diagnostics, Doctors Data, IntellxxDNA, RadNet, and Norcal Imaging for providing diagnostics for the study. We also thank Brainreader ApS for providing the Neuroreader imaging software for analyses. For clinical support, we acknowledge Tereasa Simonson MD, Michael Atkinson, Derek Barber, Mac Dodds, James Gaydos DO, Doug Jaser, Lynn Kilips, Karen Preskenis, Renèe Riley-Adams, Venessa Rodriguez, Kia Sanford, and Sheila Wagner ND. We are grateful to Phyllis and James Easton for research support leading to this trial.
FUNDING
The project was funded from the Four Winds Foundation, a non-profit entity, with no additional sources of funds. The funding entity had no role in the study design, data collection, data analysis, data interpretation, or writing of the report. None of the authors received compensation for the study except from the Foundation, to the 3 performing physicians for seeing the patients, and the contract research organization (Quesgen).
CONFLICT OF INTEREST
Dr. Cyrus Raji is an Editorial Board Member of this journal but was not involved in the peer-review process nor had access to any information regarding its peer-review. He received consulting fees from Brainreader ApS, Apollo Health, Neurevolution LLC, Voxelwise LLC, and the PNI Foundation. Dr. Kat Toups accepted lecture fees from BioBotanical Research ($1,000) in 2021. Dr. Mouna Attarha is an employee and senior research scientist at Posit Science, the developer of BrainHQ. and is a shareholder of Posit Science stock. Dr. Dale Bredesen received consulting fees from Life Seasons ($10,0000 per month) and Apollo Health ($10,000 per month), and owns equity in Apollo Health (no current value). Dr. Sharon Hausman-Cohen is the Medical Director of IntellxxDNA which was the genomics platform used in the study. We did not sponsor the study but did provide the genomics at a discount. Michael Jarrett owns equity of the company that provided data management services and support for study operations for this study. He owns other equities in his personal portfolio, but none that pertain to the execution of this study. All other authors have no conflict of interest to report.
DATA AVAILABILITY
The data supporting the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.