Curbing the major and growing threats from invasive alien species is urgent and achievable.

Although invasive alien species have long been recognized as a major threat to nature and people, until now there has been no comprehensive global review of the status, trends, drivers, impacts, management and governance challenges of biological invasions. The Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) Thematic Assessment Report on Invasive Alien Species and Their Control (hereafter 'IPBES invasive alien species assessment') drew on more than 13,000 scientific publications and reports in 15 languages as well as Indigenous and local knowledge on all taxa, ecosystems and regions across the globe. Therefore, it provides unequivocal evidence of the major and growing threat of invasive alien species alongside ambitious but realistic approaches to manage biological invasions. The extent of the threat and impacts has been recognized by the 143 member states of IPBES who approved the summary for policymakers of this assessment. Here, the authors of the IPBES assessment outline the main findings of the IPBES invasive alien species assessment and highlight the urgency to act now.

Analysis of Unique Motility of the Unicellular Green Alga Chlamydomonas reinhardtii at Low Temperatures down to -8 °C.

Previous studies of motility at low temperatures in Chlamydomonas reinhardtii have been conducted at temperatures of up to 15 °C. In this study, we report that C. reinhardtii exhibits unique motility at a lower temperature range (-8.7 to 1.7 °C). Cell motility was recorded using four low-cost, easy-to-operate observation systems. Fast Fourier transform (FFT) analysis at room temperature (20-27 °C) showed that the main peak frequency of oscillations ranged from 44 to 61 Hz, which is consistent with the 60 Hz beat frequency of flagella. At lower temperatures, swimming velocity decreased with decreasing temperature. The results of the FFT analysis showed that the major peak shifted to the 5-18 Hz range, suggesting that the flagellar beat frequency was decreasing. The FFT spectra had distinct major peaks in both temperature ranges, indicating that the oscillations were regular. This was not affected by the wavelength of the observation light source (white, red, green or blue LED) or the environmental spatial scale of the cells. In contrast, cells in a highly viscous (3.5 mPa·s) culture at room temperature showed numerous peaks in the 0-200 Hz frequency band, indicating that the oscillations were irregular. These findings contribute to a better understanding of motility under lower-temperature conditions in C. reinhardtii.

Gesture imitation performance in community-dwelling older people: assessment of a gesture imitation task in the screening and diagnosis of mild cognitive impairment and dementia.

BACKGROUND: Gesture imitation, a simple tool for assessing visuospatial/visuoconstructive functions, is reportedly useful for screening and diagnosing dementia. However, gesture imitation performance in healthy older adults is largely unknown, as are the factors associated with lower performance. To address these unknowns, we examined the gesture imitation performance of a large number of community-dwelling older adults aged ≥65 years in Arao City, Kumamoto Prefecture (southern Japan). METHODS: The examiner presented the participants with eight gesture patterns and considered it a success if they could imitate them within 10 s. The success rate of each gesture imitation was calculated for three diagnostic groups: cognitively normal (CN) (n = 1184), mild cognitive impairment (MCI) (n = 237), and dementia (n = 47). Next, we reorganised the original gesture imitation battery by combining six selected gestures with the following scoring method: if the participants successfully imitated the gestures, immediately or within 5 s, two points were assigned. If they succeeded within 5-10 s, one point was assigned. The sensitivity and specificity of the battery were investigated to detect the dementia and MCI groups. Factors associated with gesture imitation battery scores were examined. RESULTS: Except one complex gesture, the success rate of imitation in the CN group was high, approximately 90%. The sensitivity and specificity of the gesture imitation battery for discriminating between the dementia and CN groups and between the MCI and CN groups were 70%/88%, and 45%/75%, respectively. Ageing, male sex, and a diagnosis of dementia or MCI were associated with lower scores on the gesture imitation battery. CONCLUSION: Gesture imitation tasks alone may not be sufficient to detect MCI. However, by combining gestures with set time limits, gesture imitation tasks can be a low-burden and effective method for detecting dementia, even in community medicine, such as during health check-ups.

The formation of a rolling larval chamber as the unique structural gall of a new species of cynipid gall wasps.

Insect galls, which often have complex external and internal structures, are believed to have adaptive significance for the survival of insects inside galls. A unique internal structure was discovered in the gall of a new cynipid species, Belizinella volutum Ide & Koyama, sp. nov., where the larval chamber could roll freely in the internal air space of the gall. Observations of the live galls using micro-computed tomography (micro-CT) revealed its formation process. The larval chamber becomes isolated from the internal parenchyma soon after the gall reaches the maximum diameter and is able to roll as the internal air space is expanding from the surrounding parenchyma to the outer gall wall. The enemy hypothesis could partly explain the adaptive significance of the unique structure of the gall of B. volutum.

Specific alien plant species predominantly deliver nectar sugar and pollen but are not preferentially visited by wild pollinating insects in suburban riparian ecosystems.

The invasion of alien plants has been rapidly proceeding worldwide due to urbanisation. This might be beneficial to wild pollinating insects, since some alien plant species have large flowers and/or long flowering periods, which can increase nectar sugar and pollen availability. To determine the relative contribution of alien plants to floral resource supply and whether resource-rich alien plants, if any, serve as an important food source of pollinating insects, we performed year-round field observations in suburban riverbanks. We quantified the per-unit-area availability of nectar sugar and pollen delivered by alien and native flowering species and counted wild flower visitors (bees and wasps, hoverflies and butterflies) per plant species. The available nectar sugar and pollen per area were predominantly delivered by a few specific alien species, and the relative contribution of other species to floral resource provision was low throughout the period that wild flower visitors were observed. Nonetheless, the resource-rich alien plants were not visited by as many insects as expected based on their contribution to resource provision. Rather, on a yearly basis, these plants received equal or even fewer visits than other flowering species, including resource-poor natives. We show that despite their great contribution to the gross floral resource supply, resource-rich alien plants do not serve as a principal food source for wild pollinating insects, and other plants, especially natives, are still needed to satisfy insect demand. For the conservation of pollinating insects in suburban ecosystems, maintaining floral resource diversity would be more beneficial than having an increase in gross floral resources by allowing the dominance of specific alien plants.

The trajectory of non-depressed suicidal ideation in community-dwelling older people in a rural area in Japan: a prospective longitudinal study with a 3-year follow-up.

BACKGROUND: Suicidal ideation is closely related to severe suicidal behaviour and is an important predictor of suicide attempt and completion, including in older people. Older people tend to have many opportunities to be conscious of death, and may have vague suicidal ideation because of various loss experiences, even if they are not depressed. We hypothesised that suicidal ideation among older people might be a risk factor for later transition to depression. The present study aimed to clarify risk factors that predict the incidence of depression in older people 3 years post-baseline in a rural area of Japan, and to examine the subsequent course of depression among non-depressed older people with suicidal ideation. METHODS: In 2015 and 2018, survey questionnaires were mailed to residents aged 65 years and over living in a rural area in Japan. Participants were divided into a depression group and a non-depression group using 15-item Geriatric Depression Scale scores 3 years post-baseline. Logistic regression analysis was used to identify predictive factors of late-life depression 3 years post-baseline. RESULTS: We received 597 valid responses, with a 3-year follow-up rate of 78.8%. Regarding suicidal ideation, 6.7% of non-depressed older people exhibited suicidal ideation at baseline. Of these, 9.8% exhibited depression after 3 years post-baseline. Logistic regression analysis indicated that development of late-life depression is significantly associated with suicidal ideation, being female, and poor health-related quality of life (HRQOL). CONCLUSIONS: The results revealed that suicidal ideation, being female, and poor HRQOL were predictive factors of the development of late-life depression 3 years post-baseline in a rural area of Japan. These findings provide novel information regarding the transition to depression among community-dwelling older people who are not depressed but have suicidal ideation. Whereas suicidal ideation is considered to be a symptom of depression, the current results suggest that suicidal ideation may precede depression in some older people.

Comparison of caregiver burden between dementia with Lewy bodies and Alzheimer's disease.

BACKGROUND: Caring for patients with dementia with Lewy bodies (DLB) would be more stressful for their caregivers than those with Alzheimer's disease (AD). In this study, we compared levels of caregiver burden and the possible influential factors on the caregiver burden between DLB and AD. METHODS: Ninety-three DLB patients and 500 AD patients were selected from the Kumamoto University Dementia Registry. Caregiver burden, neuropsychiatric symptoms, basic activities of daily living (BADL) and instrumental activities of daily living (IADL) were assessed by the Japanese version of the Zarit Caregiver Burden Interview (J-ZBI), the Neuropsychiatric Inventory (NPI), the Physical Self-Maintenance Scale (PSMS), and the Lawton IADL scale, respectively. RESULTS: Despite the comparable Mini-Mental State Examination score, the J-ZBI score was significantly higher in the DLB group than the AD group (P = 0.012). A stepwise multiple regression analysis revealed that IADL score (ß = -0.23, P = 0.049), PSMS score (ß = -0.31, P = 0.010), disinhibition (ß = 0.22, P = 0.008), and anxiety (ß = 0.19, P = 0.027) were significantly associated with J-ZBI score in DLB. In AD, caregiver's relationship with patient (child) (ß = 0.104, P = 0.005), caregiver's gender (female) (ß = 0.106, P = 0.004), IADL score (ß = -0.237, P < 0.001), irritability (ß = 0.183, P < 0.001), apathy (ß = 0.132, P = 0.001), agitation (ß = 0.118, P = 0.007), and aberrant motor behaviour (ß = 0.107, P = 0.010) were associated with caregiver burden. CONCLUSIONS: Caring for DLB patients caused a higher degree of caregiver burden than AD patients in the same level of cognitive decline. The factors responsible for the caregiver's burden were different between DLB and AD. The caregiver burden for DLB patients was associated with the disability of basic ADL, IADL impairment, anxiety and disinhibition.

Plant Gall Diversity in Burned Semi-natural Grasslands in Japan.

We surveyed woody plants, including oaks and chestnuts (Quercus L. and Castanea Mill.), and recorded the inhabiting galls induced by oak gall wasps (Hymenoptera: Cynipidae: Cynipini) at seven Japanese semi-natural grassland sites maintained by traditional regular burning with two of the seven abandoned grassland areas. Woody plants were established in all burned and abandoned grasslands. Oak species were found at four of the seven sites. In total, 15 types of cynipid galls were recorded at all four sites where oak species were found. However, the occurrence of species was site-specific for host trees and cynipid galls. Although a few ecological studies of oak gall wasps inhabiting grassland environments, which have rapidly decreased in recent decades, have been conducted, this study suggests that semi-natural grasslands may be potential habitats for oak gall wasps and their host trees, and we provide a checklist of oak gall wasps with host oak records in semi-natural grasslands throughout Japan.

Impact of age on the cerebrospinal fluid spaces: high-convexity and medial subarachnoid spaces decrease with age.

BACKGROUND: Impaired cerebrospinal fluid (CSF) dynamics may contribute to the pathophysiology of neurodegenerative diseases, and play a crucial role in brain health in older people; nonetheless, such age-related changes have not been well elucidated. Disproportionately enlarged subarachnoid-space hydrocephalus (DESH) is a neuroimaging phenotype of idiopathic normal-pressure hydrocephalus, originating from impaired CSF dynamics, and closely associated with aging. This study aimed to investigate the pathophysiology of DESH and determine age-related changes in CSF dynamics. METHODS: Using magnetic resonance imaging, we investigated the pathophysiology of DESH by quantitatively evaluating the volumes of DESH-related regions (ventricles [VS], Sylvian fissure [SF], and subarachnoid spaces at high convexity and midline [SHM]) and brain parenchyma in community-dwelling individuals aged ≥ 65 years. DESH-related regions were assessed using a visual rating scale, and volumes measured using voxel-based morphometry. Brain parenchyma volumes were measured using FreeSurfer software. RESULTS: Data from 1,356 individuals were analyzed, and 25 (1.8%) individuals had DESH. Regarding the relationships between the volume of each CSF space and age, VS and SF volumes increased with age, whereas SHM volume did not increase. VS and SF volumes increased as the whole brain volume decreased, whereas SHM volume did not increase even if the whole brain volume decreased; that is, SHM did not expand even if brain atrophy progressed. Moreover, lower Mini-Mental State Examination scores were significantly associated with lower SHM volume and higher VS volume. These associations remained significant even when individuals with DESH were excluded. CONCLUSIONS: This study showed that the volume of high-convexity and medial subarachnoid spaces did not expand and tended to decrease with age; the human brain continuously progresses toward a "DESH-like" morphology with aging in community-dwelling older persons (i.e., DESH might be an "accelerated aging stage" rather than an "age-related disorder"). Our results indicated that brain atrophy may be associated with the development of "DESH-like" morphology. In addition, this morphological change, as well as brain atrophy, is an important condition associated with cognitive decline in older adults. Our findings highlight the importance of investigating the aging process of CSF dynamics in the human brain to preserve brain health in older people.

Brain structural alterations and clinical features of cognitive frailty in Japanese community-dwelling older adults: the Arao study (JPSC-AD).

Cognitive frailty (CF) is a clinical condition defined by the presence of both mild cognitive impairment (MCI) and physical frailty (PF). Elderly with CF are at greater risk of dementia than those with MCI or PF alone, but there are few known clinical or neuroimaging features to reliably distinguish CF from PF or MCI. We therefore conducted a population-based cross-sectional study of community elderly combining physical, cognitive, neuropsychiatric, and multisequence magnetic resonance imaging (MRI) evaluations. The MRI evaluation parameters included white matter (WM) lesion volumes, perivascular and deep subcortical WM lesion grades, lacunar infarct prevalence, microbleed number, and regional medial temporal lobe (MTL) volumes. Participants were divided into 4 groups according to the presence or absence of MCI and PF-(1) no MCI, PF (n = 27); (2) no PF, MCI (n = 119); (3) CF (MCI + PF) (n = 21), (4) normal controls (n = 716). Unique features of CF included shorter one-leg standing time; severe depressive symptoms; and MRI signs of significantly more WM lesions, lacunar infarcts, small-vessel disease lesions, microbleeds, and reduced MTL volumes. These unique deficits suggest that interventions for CF prevention and treatment should focus on motor skills, depressive symptoms, and vascular disease risk factor control.

Relationship between preoperative anxiety and onset of delirium after cardiovascular surgery in elderly patients: focus on personality and coping process.

BACKGROUND: Postoperative delirium is associated with increased mortality. Therefore, it is important to manage delirium during the entire perioperative period. Preoperative anxiety is associated with poor prognosis in postoperative patients who have undergone cardiovascular surgery. This study aims to investigate the relationship between preoperative anxiety and onset of delirium after cardiovascular surgery in elderly patients (aged 65 years or older), considering the individual psychological characteristics, such as personality and stress coping skills in response to anxiety, as confounding factors. METHODS: This prospective study included patients aged >65 years in a preoperative state before undergoing cardiovascular surgery. Subjects were divided into two groups based on whether they experienced postoperative delirium, or not. We compared clinical and demographic factors, preoperative psychiatric and psychological factors, and intraoperative and perioperative physical factors between the control and delirium groups. Multiple imputations were used to account for missing data. RESULTS: Out of 168 subjects enrolled in this study, 26 (15.5%) developed postoperative delirium. Univariate analysis showed significant differences in age (P = 0.027), cognitive function (P = 0.007), agreeableness (P = 0.029), and the Acute Physiology and Chronic Health Evaluation-II (APACHE-II) score (P = 0.023) between the delirium and control groups. Multiple logistic regression analysis did not identify a significant association between preoperative anxiety and the onset of postoperative delirium. However, age (odds ratio (OR) = 1.114, P = 0.018), agreeableness (OR = 0.555, P = 0.008), and the APACHE-II score (OR = 1.227, P = 0.008) were identified as risk factors for postoperative delirium. CONCLUSION: Agreeableness, one of the personality traits associated with preoperative anxiety, appears to be involved in the development of postoperative delirium as an independent psychological factor, regardless of age or physical factors.

Disconnection between conservation awareness and outcome: Identifying a bottleneck on non-native species introduction via footwear.

Unintentional seed introduction mediated by visitor's clothing and footwear is a major source of biological invasion into natural areas. To effectively avert these unintentional introductions, we must understand the links that connect relevant knowledge and desired outcome (i.e., seeds not carried on visitor's belongings); however, until now, these links have not been examined. Here, we investigated the links among a visitor's knowledge about biological invasion, awareness of biological invasion, behavior to prevent introduction (cleaning footwear), and being a seed carrier to identify a potential bottleneck between visitor knowledge and ecological outcome. In order to achieve this, we conducted a questionnaire survey and soil sampling from the footwear of visitors to an alpine national park. Soil samples (n = 344) were subjected to a germination experiment, and the number of emerged seedlings was recorded for each sample. We observed seedlings emerging from 27 soil samples (7.8 % of visitors; 44 seedlings in total), comprising non-native species. The degree of a visitor's knowledge about biological invasion increased with the increase in the degree of awareness. However, the high degree of awareness was not linked with the actual behavior of cleaning their footwear before the visit, although footwear cleaning effectively reduced the number of emerged seedlings. We found the lack of a clear association between awareness and behavior (cleaning the footwear) to be the bottleneck. We also investigated the major sources of knowledge about human-mediated seed introduction from footwear and found that television was the most important information source. The key to effectively preventing negative impacts on ecosystems caused by the introduction of non-native species could be to revise methods for informing the community, which will help overcome the bottleneck between awareness and behavior.

Clinical features of behavioral symptoms in patients with semantic dementia: Does semantic dementia cause autistic traits?

OBJECTIVE: To investigate the behavioral characteristics of semantic dementia (SD) using an instrument originally developed for patients with autism spectrum disorder. METHODS: The behavioral symptoms of 20 patients with SD and 20 patients with Alzheimer's disease (AD) in both the preclinical state and the dementia state were evaluated using the Pervasive Developmental Disorders Autism Society Japan Rating Scale (PARS). RESULTS: The SD group showed high prevalence in four behaviors related to stereotypy and social impairment: eating very few food items, selfishness, difficulty in recognizing others' feeling and thoughts, and interpreting language literally. Scores on the PARS short version, which is sensitive for diagnosis of autism spectrum disorder, were significantly higher in the dementia state than in the preclinical state in both the SD (11.5 ± 6.0 and 1.7 ± 2.5, respectively; t (19) = 6.7, p < 0.001) and AD (6.9 ± 4.6 and 1.7 ± 2.0, respectively; t (19) = 5.1, p < 0.001) groups. PARS short version scores after dementia onset increased in both the SD and AD groups, although the increase was significantly larger in the SD group (F = 5.6, p = 0.023). Additionally, a significantly higher rate of patients exceeded the cutoff score for autism diagnosis in the dementia state in the SD group (75%) than in the AD group (40%; χ2 = 5.0, p = 0.025). PARS scores in the dementia state were significantly correlated with illness duration (r = 0.46, p = 0.04) and Mini-Mental State Examination scores (r = -0.75, p < 0.001) in the SD group only. CONCLUSIONS: Although SD and autism spectrum disorder are etiologically distinct diseases, patients with semantic dementia behave like those with autism spectrum disorder. Our findings suggest the symptomatic similarity of the two disorders.

Relationship between Performance on the Mini-Mental State Examination Sub-Items and Activities of Daily Living in Patients with Alzheimer's Disease.

Mini-mental state examination (MMSE) subitems provide useful information about the cognitive status of patients with Alzheimer's disease (AD). If the relationship between MMSE subitems and activities of daily living (ADL) can be shown, the performance of sub-items can predict ADL status and may provide useful information for early ADL intervention. Therefore, the purpose of this study was to investigate the relationship between MMSE subitem scores and ADL. The study sample consisted of 718 patients with AD. Logistic regression analysis using the Physical Self-maintenance Scale (PSMS) and Lawton's Instrumental ADL (L-IADL) was performed with each of the subitems as the dependent variables and the MMSE subitem as the independent variable. As a result, the subitems of MMSE, which are strongly related to each item in PSMS differed (e.g., toilet: registration odds ratio 3.00, grooming: naming 3.66). In the case of L-IADL, most items were strongly associated with "writing" (e.g., shopping: odds ratio 4.29, laundry 3.83). In clinical practice, we often focus only on the total MMSE score in patients with AD. However, the relationship between each MMSE subitem and ADL suggested in this study may be useful information that can be linked to ADL care from the performance of the MMSE subitem.

Age-Related Changes in Instrumental and Basic Activities of Daily Living Impairment in Older Adults with Very Mild Alzheimer's Disease.

BACKGROUND/AIMS: Age-related changes in impairments in activities of daily living (ADL) in older adults with very mild Alzheimer's disease (vmAD) have been scarcely explored. We clarified the characteristics of ADL impairment and examined how ADL impairments differed by age in such patients compared with community-dwelling cognitively normal older adults. METHODS: The participants were 107 older adults with vmAD (Mini-Mental State Examination [MMSE] score ≥24), all of whom were first-visit outpatients at the Dementia Clinic of the Department of Neuropsychiatry, Kumamoto University Hospital. The controls were 682 community-dwelling older adults who participated in the 3rd Nakayama Study with MMSE score ≥24. We examined the association of instrumental and basic ADL (IADL and BADL, respectively) independence with the odds of vmAD using multiple logistic regression analysis and determined differences in ADL impairment by age using age- and sex-matched analysis. RESULTS: Impairments in handling finances (OR 57.08), managing medication (OR 5.13), and dressing (OR 3.35; BADL) were associated with greater odds of vmAD. Among those aged 65 years and above, there were fewer patients with vmAD than healthy controls who could independently handle finances and medication. Among patients with vmAD, the percentages of those who could independently manage shopping, food preparation, and housekeeping only decreased after age 74. Age-related decreases in independence were observed in few BADL items; these, however, were temporary. CONCLUSIONS: Patients with vmAD show significantly decreased IADL independence from early old age.

Relationship between executive dysfunction and neuropsychiatric symptoms and impaired instrumental activities of daily living among patients with very mild Alzheimer's disease.

OBJECTIVES: Patients with Alzheimer's disease (AD) experience a gradual loss in their ability to perform instrumental activities of daily living (IADLs) from the early stage. A better understanding of the possible factors associated with IADL decline is important for the development of effective rehabilitation and support programs for patients with AD. Thus, we examined the relationships between comprehensive cognitive functions and neuropsychiatric symptoms and IADLs in patients with very mild AD. METHODS: In total, 230 outpatients with probable AD were recruited from the Memory Clinic at Kumamoto University Hospital between May 2007 and October 2016. All patients scored ≥21 points on the Mini-Mental State Examination at the first assessment. Relationships between the subdomains of the Lawton IADL scale and neuropsychological/neuropsychiatric tests were examined by multiple regression analysis. All analyses were performed separately in men and women. RESULTS: In female patients, scores on the Frontal Assessment Battery were significantly associated with telephone use ability, shopping, and ability to handle finances. Apathy scores in the Neuropsychiatric Inventory (NPI) were associated with telephone use ability, housekeeping, responsibility for own medications, and ability to handle finances. NPI agitation scores were associated with food preparation and housekeeping. Geriatric Depression Scale scores were associated with telephone use ability and ability to handle finances. In male patients, only NPI apathy scores were associated with telephone use ability. CONCLUSIONS: These results suggest the importance of properly assessing executive function, depression, and apathy at interventions for impaired IADLs among female patients with very mild AD.

Cerebral Microbleeds Are Associated with Cerebral Hypoperfusion in Patients with Alzheimer's Disease.

BACKGROUND: Although cerebral microbleeds (CMBs) are commonly observed in patients with Alzheimer's disease (AD), their clinical relevance for AD remains unclear. OBJECTIVE: We investigated the significance of CMBs in AD by examining the relationship between CMBs and cerebral blood flow (CBF) in patients with AD. METHODS: Thirty-four patients (aged 77.9±7.6 years; 17 men) with probable AD and multiple (≥8) CMBs were selected from 394 consecutive patients. For each lobe of the brain, the correlation between the number of CMBs observed on susceptibility-weighted images and the decrease in CBF observed on single-photon emission computed tomography was assessed. RESULTS: The number of microbleeds was significantly correlated with the severity of decrease in the occipital lobe (Spearman's r = 0.531, p < 0.001) and temporal lobe (r = 0.437, p < 0.001) but not in the frontal lobe (r = 0.201, p = 0.101) and parietal lobe (r = 0.178, p = 0.146). These results were unchanged in the partial correlational analysis after controlling the effect of other small vessel disease such as lacunars and white matter hyperintensities. CONCLUSION: Multiple CMBs are associated with cerebral hypoperfusion in AD. The effects of CMBs on CBF differed according to brain location, possibly reflecting different distributions of the underlying cerebral amyloid angiopathy and AD-related histopathology, such as neurofibrillary tangles.

Caregiver Burden in Semantic Dementia with Right- and Left-Sided Predominant Cerebral Atrophy and in Behavioral-Variant Frontotemporal Dementia.

BACKGROUND: Caregiver burden is a serious concern for family caregivers of dementia patients, but its nature is unclear in patients with semantic dementia (SD). This study aimed to clarify caregiver burden for right- (R > L) and left-sided (L > R) predominant SD versus behavioral-variant frontotemporal dementia (bvFTD) patients. METHODS: Using the Japanese version of the Zarit Burden Interview (ZBI) and the Neuropsychiatric Inventory, we examined caregiver burden and behavioral and psychological symptoms of dementia (BPSD) in 43 first-visit outpatient/family caregiver dyads (bvFTD, 20 dyads; SD [L > R], 13 dyads; SD [R > L], 10 dyads). RESULTS: We found a significant difference in ZBI score between the 3 diagnostic groups. Post hoc tests revealed a significantly higher ZBI score in the bvFTD than in the SD (L > R) group. The ZBI scores in the SD (L > R) and SD (R > L) groups were not significantly different, although the effect size was large. Caregiver burden was significantly correlated with BPSD scores in all groups and was correlated with activities of daily living and instrumental activities of daily living decline in the bvFTD and SD (R > L) groups. CONCLUSION: Caregiver burden was highest in the bvFTD group, comparatively high in the SD (R > L) group, and lowest in the SD (L > R) group. Adequate support and intervention for caregivers should be tailored to differences in caregiver burden between these patient groups.