Frequency and Pathophysiology of Apathy in Huntington Disease: A Systematic Review and Meta-Analysis

Frequency of depression in Huntington's disease: A systematic review and meta-analysis

BackgroundHuntington's disease (HD) is a hereditary neurodegenerative disease characterized by a combination of motor, cognitive, and mental health issues, with depression being the most common. Despite its importance, the relationship between depression and disease progression is still debatable.ObjectiveThe primary objective of this study was to examine the frequency of depression across different disease stages in individuals with HD. We also explored the associations between depression and other HD-related factors.MethodsThis systematic review comprehensively searched MEDLINE, APA PsycINFO, and Embase databases for studies on depression in individuals with HD. Pooled depression frequencies were calculated for premanifest and manifest HD. Depression was analyzed based on HD functional stages and diagnostic tools, alongside reviewing its association with various HD factors.ResultsWe assessed 6523 records and included 104 studies. Our meta-analyses revealed that the overall frequency of depression was higher in manifest HD compared to premanifest HD (0.38 vs. 0.23). However, the progression of depression did not follow a consistent pattern, with peaks occurring in earlier rather than later stages. Additionally, the frequency of depression was lower in studies using diagnostic criteria compared to those using clinical scales (0.25 vs. 0.42).ConclusionsOur findings showed that the rate of depression is high in HD and varies depending on the disease stage and the criteria used. This emphasizes the necessity for tailored and unified diagnostic criteria for depression in HD.

Apathy and Functional Status in Early-Stage Huntington's Disease

OBJECTIVE

Apathy is common in Huntington's disease (HD) and difficult to treat. Multiple recent calls have been made to increase understanding of apathy across the spectrum of HD severity. Functional status is an important outcome in HD trials; however, no consensus currently exists regarding the impact of apathy on functional status in HD. The authors aimed to identify correlates of apathy and effects on functional status in a primarily early-stage HD sample.

METHODS

This study included secondary analyses of data from a study of neuropsychiatric symptoms in a clinical HD sample. Spearman correlation analyses were used to assess the relationships between apathy (with the Frontal Systems Behavior Scale-Apathy [FrSBe-Apathy] subscore), clinical variables, and patient-reported outcomes. To assess the association of apathy with functional status, two multiple regression analyses were performed, with a different functional status measure (Adult Functional Adaptive Behavior [AFAB] scale or Total Functional Capacity [TFC] scale) as the dependent variable in each analysis.

RESULTS

Statistically significant correlates of apathy included the Quality of Life in Neurological Disorders (Neuro-QoL) Satisfaction With Social Roles and Activities and Neuro-QoL Positive Affect and Well-Being scores (N=70 patients). Univariate correlation analyses also revealed statistically significant associations of FrSBe-Apathy scores with both functional status measures. In the multiple regression analyses, apathy significantly contributed to variability in functional status as measured by both the AFAB (N=49 patients) and TFC (N=56 patients) scales.

CONCLUSIONS

These results underscore the need to address apathy as a target for improving functional status, social satisfaction, and well-being in HD, even for individuals with early-stage HD.

[Psychiatric symptoms of Huntington's disease]

Huntington's disease (HD) is an autosomal dominant inherited disease, which leads to motor, cognitive and psychiatric symptoms. The diagnosis can be confirmed by genetic testing for extended CAG repeats in the Huntingtin gene. Mental and behavioral symptoms are common in HD and can appear several years before the onset of motor symptoms. The psychiatric symptoms include apathy, depression, anxiety, obsessive-compulsive symptoms and, in some cases, psychoses and aggression. These are currently restricted to symptomatic treatment as disease-modifying treatment approaches are still under investigation. The current clinical practice is based on expert opinions as well as experience with the treatment of similar symptoms in other neurological and mental health diseases. This article provides an overview of the complex psychiatric manifestations of HD, the diagnostic options and the established pharmacological and nonpharmacological treatment approaches.

Pathomechanisms of behavioral abnormalities in Huntington disease: an update

Huntington disease (HD), a devastating autosomal-dominant neurodegenerative disease caused by an expanded CAG trinucleotide repeat, is clinically characterized by a triad of symptoms including involuntary motions, behavior problems and cognitive deficits. Behavioral symptoms with anxiety, irritability, obsessive-compulsive behaviors, apathy and other neuropsychiatric symptoms, occurring in over 50% of HD patients are important features of this disease and contribute to impairment of quality of life, but their pathophysiology is poorly understood. Behavior problems, more frequent than depression, can be manifest before obvious motor symptoms and occur across all HD stages, usually correlated with duration of illness. While specific neuropathological data are missing, the relations between gene expression and behavior have been elucidated in transgenic models of HD. Disruption of interneuronal communications, with involvement of prefronto-striato-thalamic networks and hippocampal dysfunctions produce deficits in multiple behavioral domains. These changes that have been confirmed by multistructural neuroimaging studies are due to a causal cascade linking molecular pathologies (glutamate-mediated excitotoxicity, mitochondrial dysfunctions inducing multiple biochemical and structural alterations) and deficits in multiple behavioral domains. The disruption of large-scale connectivities may explain the variability of behavior profiles and is useful in understanding the biological backgrounds of functional decline in HD. Such findings offer new avenues for targeted treatments in terms of minimizing neurobehavioral impairment in HD.

Therapeutic advances in neural regeneration for Huntington's disease

Huntington's disease is a neurodegenerative disease caused by the expansion mutation of a cytosine-adenine-guanine triplet in the exon 1 of the HTT gene which is responsible for the production of the huntingtin (Htt) protein. In physiological conditions, Htt is involved in many cellular processes such as cell signaling, transcriptional regulation, energy metabolism regulation, DNA maintenance, axonal trafficking, and antiapoptotic activity. When the genetic alteration is present, the production of a mutant version of Htt (mHtt) occurs, which is characterized by a plethora of pathogenic activities that, finally, lead to cell death. Among all the cells in which mHtt exerts its dangerous activity, the GABAergic Medium Spiny Neurons seem to be the most affected by the mHtt-induced excitotoxicity both in the cortex and in the striatum. However, as the neurodegeneration proceeds ahead the neuronal loss grows also in other brain areas such as the cerebellum, hypothalamus, thalamus, subthalamic nucleus, globus pallidus, and substantia nigra, determining the variety of symptoms that characterize Huntington's disease. From a clinical point of view, Huntington's disease is characterized by a wide spectrum of symptoms spanning from motor impairment to cognitive disorders and dementia. Huntington's disease shows a prevalence of around 3.92 cases every 100,000 worldwide and an incidence of 0.48 new cases every 100,000/year. To date, there is no available cure for Huntington's disease. Several treatments have been developed so far, aiming to reduce the severity of one or more symptoms to slow down the inexorable decline caused by the disease. In this context, the search for reliable strategies to target the different aspects of Huntington's disease become of the utmost interest. In recent years, a variety of studies demonstrated the detrimental role of neuronal loss in Huntington's disease condition highlighting how the replacement of lost cells would be a reasonable strategy to overcome the neurodegeneration. In this view, numerous have been the attempts in several preclinical models of Huntington's disease to evaluate the feasibility of invasive and non-invasive approaches. Thus, the aim of this review is to offer an overview of the most appealing approaches spanning from stem cell-based cell therapy to extracellular vesicles such as exosomes in light of promoting neurogenesis, discussing the results obtained so far, their limits and the future perspectives regarding the neural regeneration in the context of Huntington's disease.

The effect of Huntington's disease on cognitive and physical motivation

Apathy is one of the most common neuropsychiatric features of Huntington's disease. A hallmark of apathy is diminished goal-directed behaviour, which is characterized by a lower motivation to engage in cognitively or physically effortful actions. However, it remains unclear whether this reduction in goal-directed behaviour is driven primarily by a motivational deficit and/or is secondary to the progressive cognitive and physical deficits that accompany more advanced disease. We addressed this question by testing 17 individuals with manifest Huntington's disease and 22 age-matched controls on an effort-based decision-making paradigm. Participants were first trained on separate cognitively and physically effortful tasks and provided explicit feedback about their performance. Next, they chose on separate trials how much effort they were willing to exert in each domain in return for varying reward. At the conclusion of the experiment, participants were asked to rate their subjective perception of task load. In the cognitive task, the Huntington's disease group were more averse to cognitive effort than controls. Although the Huntington's disease group were more impaired than controls on the task itself, their greater aversion to cognitive effort persisted even after controlling for task performance. This suggests that the lower levels of cognitive motivation in the Huntington's disease group relative to controls was most likely driven by a primary motivational deficit. In contrast, both groups expressed a similar preference for physical effort. Importantly, the similar levels of physical motivation across both groups occurred even though participants with Huntington's disease performed objectively worse than controls on the physical effort task, and were aware of their performance through explicit feedback on each trial. This indicates that the seemingly preserved level of physical motivation in Huntington's disease was driven by a willingness to engage in physically effortful actions despite a reduced capacity to do so. Finally, the Huntington's disease group provided higher ratings of subjective task demand than controls for the cognitive (but not physical) effort task and when assessing the mental (but not the physical) load of each task. Together, these results revealed a dissociation in cognitive and physical motivation deficits between Huntington's disease and controls, which were accompanied by differences in how effort was subjectively perceived by the two groups. This highlights that motivation is the final manifestation of a complex set of mechanisms involved in effort processing, which are separable across different domains of behaviour. These findings have important clinical implications for the day-to-day management of apathy in Huntington's disease.

Apathy in persons living with HIV disease: A systematic narrative review

BACKGROUND

Apathy was identified as a feature of HIV early in the epidemic; however, there are no systematic reviews of the diverse literature on the sociodemographic and clinical correlates of apathy in HIV disease.

METHODS

The current study adopted a hybrid systematic-narrative review methodology in which we used PRISMA guidelines to identify, summarize, and critique peer-reviewed, empirical studies of apathy in HIV disease in the era of combination antiretroviral therapy.

RESULTS

A total of 34 studies of apathy in persons living with HIV (PLWH) were identified. Findings across these studies showed that apathy was reliably related to the structure of grey and white matter pathways commonly implicated in apathy, poorer everyday functioning, education, and other neuropsychiatric symptoms (e.g., depression). Apathy was not reliably associated with age, sex, race/ethnicity, cognition, and clinical markers of HIV disease.

LIMITATIONS

The current review does not provide rigorous quantitative estimates of clinical correlates of apathy, and the exclusion criteria of non-English and non-peer reviewed publications introduces risk of bias and Type I error.

CONCLUSIONS

Apathy occurs at higher rates in PLWH and is linked to neuroanatomical differences, as well as negative outcomes for everyday functions, aspects of neurocognition, and neuropsychiatric symptoms. As such, apathy is an important component to consider in the clinical assessment, diagnosis, and management of neurocognitive disorders in PLWH. Future work is needed to replicate existing findings with larger sample sizes and longitudinal designs, examine apathy as a multi-dimensional construct, and develop evidence-based treatments for apathy in PLWH.