Family carers of people with dementia are more likely to experience moderate to high carer burden (Cullinan et al., Reference Cullinan, Fealy, Lafferty, O’Shea and Teahan2021) and carers of people with young-onset dementia (YOD) defined as dementia with symptom onset before 65 years of age (Rossor et al., Reference Rossor, Fox, Mummery, Schott and Warren2010), face additional challenges. Younger patients tend to have a faster disease progression with more atypical presentations, including a higher prevalence of language impairment, agnosia, and behavioral involvement (Mendez, Reference Mendez2006). Community support for these young patients tends to be minimal and the loss of employment due to dementia results in a greater socioeconomic burden (Kandiah et al., Reference Kandiah, Wang, Lin, Nyu, Lim, Ng, Hameed and Wee2016). Dementia in the young have a higher genetic susceptibility and positive family history would also affect the carer burden in view of the previous negative experience with dementia outcomes (Rossor et al., Reference Rossor, Fox, Mummery, Schott and Warren2010).

Carer burden has been associated with factors related to the clinical features of the patient including presence of behavioral and psychological disorders (BPSD) (Feast et al., Reference Feast, Moniz-Cook, Stoner, Charlesworth and Orrell2016; Liu et al., Reference Liu, Liu, Wang, Shi, Zhou, Li, Yu and Ji2018). Carers of people with YOD suffer high levels of burden but the difference when compared to late-onset dementia is not conclusive (van Vliet et al., Reference van Vliet, de Vugt, Bakker, Koopmans and Verhey2010). A study that evaluated 183 patient-carer dyads to compare carer burden in YOD (n = 57) with late-onset dementia (n = 126) found higher levels of carer burden in YOD (Lim et al., Reference Lim, Zhang, Lim, Choong, Silva, Ng, Kandiah and Grill2018). They reported that risk factors for high caregiver burden in YOD included family history of dementia and behavioral symptoms, which included disinhibited behavior, delusions, and apathy as measured by neuropsychiatric inventory-questionnaire (Cummings et al., Reference Cummings, Mega, Gray, Rosenberg-Thompson, Carusi and Gornbein1994; Lim et al., Reference Lim, Zhang, Lim, Choong, Silva, Ng, Kandiah and Grill2018).

Few have investigated the role of individual symptoms of BPSD in impacting on carer’s burden. A systematic review, which included forty medium and high quality quantitative papers, showed depressive behaviors were the most distressing for caregivers followed by agitation/aggression and apathy (Feast et al., Reference Feast, Moniz-Cook, Stoner, Charlesworth and Orrell2016). The authors had included “aged” in the key terms for search and hence included studies mostly with older adults (Feast et al., Reference Feast, Moniz-Cook, Stoner, Charlesworth and Orrell2016). In a study wherein 92 consecutive caregivers of YOD were recruited from the Cognitive Neurology Clinics of Modena, Northern Italy, BPSD was one of the determinants of carer burden (total NPI score), however, individual NPI domains were not examined (Chiari et al., Reference Chiari, Pistoresi, Galli, Tondelli, Vinceti, Molinari, Addabbo and Zamboni2021). In another study that used Zarit Burden Inventory (Zarit et al., Reference Zarit, Anthony and Boutselis1987), caregiver burden was measured for 3 main clinical variants of Frontotemporal dementia (FTD) — behavioral variant frontotemporal dementia (bvFTD, n = 17), semantic dementia (SemDem, n = 20), and progressive nonfluent aphasia (PNFA bvFTD, n = 20), and Alzheimer disease (AD, n = 19) patients (Mioshi et al., Reference Mioshi, Foxe, Leslie, Savage, Hsieh, Miller, Hodges and Piguet2013). Caregivers of bvFTD patients reported the highest burden, whereas SemDem and PNFA caregivers reported burden similar to AD (Mioshi et al., Reference Mioshi, Foxe, Leslie, Savage, Hsieh, Miller, Hodges and Piguet2013). Behavioral changes in FTD were strongly associated with caregiver burden, however, it seemed that a combination of functional impairment and behavioral changes, rather than behavioral dysfunction alone, were the main predictors of caregiver burden (Mioshi et al., Reference Mioshi, Foxe, Leslie, Savage, Hsieh, Miller, Hodges and Piguet2013).

Most studies have reported on carer burden in dementia due to BPSD in the elderly and few studies have focussed and specifically compared between different YOD subtypes. Kang et al. (Reference Kang, Farrand, Evans, Chiu, Eratne, Kelso, Walterfang, Velakoulis and Loi2023) in a recent paper in International Psychogeriatrics, addressed these aspects and the results presented are significant as the authors compared carer burden between young-onset AD and behavioral variant frontotemporal dementia (bvFTD) for their associations with clinical correlates such as behavior problems, daily skills, and cognition. Specifically, Kang et al. (Reference Kang, Farrand, Evans, Chiu, Eratne, Kelso, Walterfang, Velakoulis and Loi2023) carried out retrospective cross-sectional study of patient-carer dyads with YOD who attended a tertiary service over a five-year period and were part of a larger study Biomarkers in younger-onset neurocognitive disorders (BeYOND study) (Loi et al., Reference Loi, Eratne, Cadwallader and Ravanfar2021). Of the 33 carers (n = 20 with AD and n = 13 with bvFTD) whose data was included, majority were females (21 females, 68%) and there were no differences in their demographics. For the patients, cognition was evaluated with Neuropsychiatry Unit Cognitive Assessment tool (NUCOG) (Walterfang et al., Reference Walterfang, Siu and Velakoulis2006) and behavioral changes with the Cambridge Behavioral Inventory-Revised (CBI-R) (Wear et al., Reference Wear, Wedderburn, Mioshi, Williams-Gray, Mason, Barker and Hodges2008). Zarit Burden Inventory-short version (Bédard et al., Reference Bédard, Molloy, Squire, Dubois, Lever and O'Donnell2001) was used to measure carer burden. The mean total NUCOG score overall was 63.6 (SD ± 16.7) indicating moderate cognitive impairment. There were no differences in domains such as memory, orientation, duration of symptoms, and caregiving period between the two groups. Compared to patients with AD, patients with bvFTD were more likely to have difficulty with stereotypic and motor behaviors. Patients with AD were found to have difficulties with everyday skills. Carer burdens were high but did not differ significantly between AD (55%, 11/20; mean = 18.5) and bvFTD (38%, 5/13; mean = 15.2). The major findings of Kang et al. (Reference Kang, Farrand, Evans, Chiu, Eratne, Kelso, Walterfang, Velakoulis and Loi2023) are that although they found overall behavioral disturbance, as well as mood and belief related, were significantly associated with carer burden in YOD, they did not find any difference in carer burden between young-onset AD and bvFTD groups. Unexpectedly they failed to find differences in behavioral disturbance between the two subtypes, which may explain the similar levels of carer burden in the two groups. Kang et al. (Reference Kang, Farrand, Evans, Chiu, Eratne, Kelso, Walterfang, Velakoulis and Loi2023) highlight the importance of clinicians routinely screening for behavioral disturbance in younger-onset dementia, irrespective of presumed pathological diagnosis. They also emphasize assessments for BPSD in the initial phase with standaridized measures. This is important especially in light of recent report of greater caregiver burden in people with apathy in mild cognitive impairment (MCI) (Connors et al., Reference Connors, Teixeira-Pinto, Ames, Woodward and Brodaty2023). Presence of mild behavioral impairment (MBI) in patients with mild cognitive impairment or subjective cognitive decline MCI has also been associated with greater carer burden, with each of the five MBI domains (affective dysregulation, impulse control, decreased motivation, social inappropriateness, and abnormal perception or thought content) showing significant association with carer burden (Sheikh et al., Reference Sheikh, Ismail, Mortby, Barber, Cieslak, Fischer, Granger, Hogan, Mackie, Maxwell, Menon, Mueller, Patry, Pearson, Quickfall, Sajobi, Tse, Wang and Smith2018).

While the Kang et al. (Reference Kang, Farrand, Evans, Chiu, Eratne, Kelso, Walterfang, Velakoulis and Loi2023) study expands on differences in carer burden in YOD subtypes such as young-onset AD and bvFTD, we must consider the strengths and limitations of the study. Kang et al. (Reference Kang, Farrand, Evans, Chiu, Eratne, Kelso, Walterfang, Velakoulis and Loi2023) used retrospective data from patients who either attended as inpatient or outpatient from a single hospital in Australia. Although the findings may not be generalizable to other settings, they add to the growing literature indicating similar behavior impairment and carer burden in YOD subtypes. Kang et al. (Reference Kang, Farrand, Evans, Chiu, Eratne, Kelso, Walterfang, Velakoulis and Loi2023) assessed cognition using the NUCOG and used Mini-Mental State Examination (Folstein et al., Reference Folstein, Folstein and McHugh1975) for an “equivalent” total score where patients were unable to complete NUCOG, which is a crude cognitive measure and limited in examining different domains. Future studies incorporating comprehensive neuropsychological testing would help to examine level of cognitive impairment and specific cognitive domains associated with carer burden. The behavior disturbance items on the CBI-R used by Kang et al. (Reference Kang, Farrand, Evans, Chiu, Eratne, Kelso, Walterfang, Velakoulis and Loi2023) do not measure different BPSD domains and sub-domains. CBI-R is a shorter version of CBI to identify disease-specific behavior patterns and includes cognition, everyday skills, and self-care as domains that should ideally be assessed separately from core behavioral problems. Ideally, behavior and daily activities skills rating scales should be able to measure different dimensions and be able to measure them independently, since they are known to be associated with carer burden as distinct factors (Feast et al., Reference Feast, Moniz-Cook, Stoner, Charlesworth and Orrell2016; Liu et al., Reference Liu, Liu, Wang, Shi, Zhou, Li, Yu and Ji2018). There is need to examine and better understand the relationship between individual BPSD and carer burden, as it is essential to determine allocation of resources and interventions for BPSD management to target these behaviors. Appropriate and timely interventions can help to ameliorate these effects and, in turn, improve the quality of life of both caregivers and patients.

Challenges with the lack of consistency in BPSD measurement (neuropsychiatric domains, frequency, or prevalence) and the measurement of caregiver well-being (the use of interchangeable terminology such as stress, strain, and burden meaning the same construct) are well known and limit the ability to reach a consensus as to which BPSD result in the most negative outcomes for caregivers (Feast et al., Reference Feast, Moniz-Cook, Stoner, Charlesworth and Orrell2016). Another important factor is caregiver characteristics which have been shown to account for twice the variance of person with dementia characteristics when reporting neuropsychiatric symptoms (Sink et al., Reference Sink, Covinsky, Barnes, Newcomer and Yaffe2006). In addition, caregiver characteristics such as gender, overload, role captivity, confidence, neuroticism, and relationship quality are significant predictors for variance in carer burden too (Campbell et al., Reference Campbell, Wright, Oyebode, Job, Crome, Bentham, Jones and Lendon2008). Hence, it is important that future studies should focus on identifying pathways for the association between individual BPSD, caregiver variables, and caregiver outcomes. It is also important to have measures that address the contextual and caregiver characteristics associated with the behavior reporting. Larger collaborative studies comprising younger subjects from different cultural and geographic regions will be also needed.

In summary, Kang et al. (Reference Kang, Farrand, Evans, Chiu, Eratne, Kelso, Walterfang, Velakoulis and Loi2023) extend previous research by not only evaluating high carer burden in YOD but also comparing them between two subtypes i.e., bvFTD and young-onset AD. Kang et al. (Reference Kang, Farrand, Evans, Chiu, Eratne, Kelso, Walterfang, Velakoulis and Loi2023) also established overall behavioral disturbance as well as mood and belief related were significantly associated with carer burden in YOD, making them an important factor for pharmacological and non-pharmacological interventions. It is important to identify the domains of BPSD from initial stages so patients and carers may benefit from appropriate and tailored interventions.