Alzheimer’s disease (AD) is a progressive neurodegenerative disease posing a tremendous burden for patients, caregivers, and health care systems. Disease symptomatology includes, most notably, impaired cognition (e.g., memory difficulties), as well as impairments in daily activities and increasing functional dependence. This constellation of symptoms results in an increasing degree of care required, often provided by family caregivers [1]. The cause of AD remains incompletely understood and currently there is no cure. Currently available treatment is aimed at improving cognitive function and managing behavioral symptoms [2].

AD is the most common form of dementia, with dementia of the Alzheimer’s type (DAT) projected to increase dramatically over the coming decades due to the aging global population [3, 4]. Precise global prevalence estimates have been difficult to establish, but approximately 4.7 million older adults in the U.S. have been estimated to have AD [5]. In Japan in 2010, 2.5 million adults were estimated to suffer from dementia, ranking Japan among nine countries with the highest number of sufferers [6].

Studies have emerged to help better understand the challenges associated with an aging population in Japan. A nationwide survey in 2012 reported prevalence of dementia among Japanese aged 65 and over to be 15.8 %, with AD the most common form, reported among 67.6 % of patients in the same survey [7]. This rate was considerably higher than previous estimates of dementia in Japan that ranged from 2.4 %–8.5 %, with AD developed by 60.8 % of participants with dementia [8, 9]. Evidence suggests that rates of AD are increasing in Japan [10, 11] and that it represents a major health concern not only in Japan but across Asia [12]. The most recent estimates of prevalence suggest an AD rate of 3.8 % in Japan [10, 13].

Beginning in 2000, Japan has implemented an insurance program and approach to long-term care providing comprehensive evaluation of the elderly, as well as in-kind care and financial support for family caregivers [14]. In 2012, to provide further support for the aging population, the Japanese government delivered the Orange Plan for elderly people with dementia. This initiative includes action plans for early detection and early diagnosis, as well as funds to continue home care after the onset of dementia [15].

As noted, care demands are significant for those diagnosed with AD. The slow, progressive nature of this disease and functional impairment associated with symptoms result in many patients being cared for primarily by family members [16]. A growing body of research suggests that the progressive burden of care associated with AD can have real and significant deleterious health consequences for these family caregivers [17].

Empirical studies suggest that family caregivers across a number of disease conditions have a greater risk of medical illness, psychological impairment, disruption of professional and personal roles, and critically, an increased risk of mortality [18–20]. At the same time, evidence suggests that some caregivers find positive effects associated with caring for a family member diagnosed with a chronic or terminal disease. Indeed, across diseases such as cancer, heart failure, and AD, studies have documented benefit-finding and meaning associated with the caregiver role, and interventions have been developed that seek to reinforce and promote the positive effects of caregiving [21–24]. Cheng and colleagues have reported positive preliminary results of a benefit-finding intervention for AD caregivers in China, with reductions in depression reported by the intervention group [22].

Aside from negative and positive effects on mental and physical health, significant costs have also been recognized to be associated with informal AD care. In fact, a recent 2013 European study found that costs associated with informal caregiving compose the majority of total societal costs linked with AD (over 50 %) and increase even further with disease severity [25]. A recent survey revealed a similar situation in Japan, with the total 2014 societal cost for dementia estimated at $145 billion and the cost of informal care estimated at $62 billion (where $1 = 100 yen) [26]. A number of deleterious effects have been revealed about caregiver burden associated with AD [27], including physical [19, 28], psychological [29, 30], social [31], and financial [32] consequences, as well as similar findings beginning to emerge in developing countries [33].

Although a number of focused studies by Arai and others have documented substantial burden among family caregivers of the elderly in Japan, as well as the challenges associated with providing care, research quantifying the degree of burden experienced by AD caregivers across multiple outcomes (encompassing not just quality of life, but also productivity, comorbidities, and resource use) in the broader population is lacking [34–40]. In addition, a qualitative study in 2008 found that a number of factors were protective against caregiver burden, including a good prior relationship between caregiver and patient, and the utilization of resources by the caregiver [41]. The authors did note that certain dyads were at greater risk (e.g., husbands caring for wives), and they recommended services be put in place to support higher-risk circumstances.

In a recent study, Kamiya and colleagues investigated factors associated with caregiving burden and found that behavioral disturbances and lower scores on the Mini-Mental State Examination (MMSE) were associated with increased burden [42]. Finally, Hirono and colleagues examined the role of caregiver burden in the eventual institutionalization or death of patients with AD in Japan. The authors followed 150 individual dyads for at least one year and found that initial caregiver burden was a significant predictor of both outcomes: death and transition of care to an institution [43]. Critically, the authors found that the early use of resources to aid in care (namely, daycare and home care services) were once again protective factors that reduced burden. The authors concluded that caregiver education was needed to increase understanding of the meaning and necessity of supportive care services and their ability to reduce caregiver burden.

Interventions targeting caregivers have been the topic of emerging research, although little has been published in Japan. A 1999 study by Hosaka and Sugiyama investigated the effects of a pilot program for AD caregivers, reporting that a 5-week educational and supportive group program resulted in significant improvements in mood and functioning among caregivers [44].

Despite the lack of nationwide research on supportive care programs in Japan, in recognition of the high degree of burden experienced by AD caregivers, Hashimoto et al. reported the beneficial effect of donepezil hydrochloride (approved for treatment of DAT) on caregiver burden, finding that caregivers of symptomatic patients reported a significant decrease in burden over the course of the 12-week trial [45]. Hishikawa et al. reported that garantamine treatment of patients with AD reduced behavioral and psychological symptoms of dementia and corresponding caregiver burden in a six-month retrospective evaluation study [46], while Kuroda et al. reported that rivastigmine was also associated with reduced caregiver burden [47]. This, along with supportive therapies, represents an important but under-researched domain of investigation.

Large-scale population-based studies, particularly those that include both urban and rural participants, and a broad range of psychosocial and economic outcomes, provide critical information that can enhance our understanding of caregiver burden, as well as helping guide the development and implementation of appropriate support services for this important and under-represented caregiver population. The current study therefore aims to add to the general literature this breadth of information, as well as help address a gap in the literature concerning the effects of AD caregiving on Japanese caregivers’ work productivity and resource use, an issue of great relevance in the context of a rapidly aging population [48]. The study will assess how family caregivers for patients with AD or dementia in Japan differed from non-caregivers in terms of their characteristics and health outcomes (i.e., comorbidities, health-related quality of life [HRQoL], productivity, and resource use).

With respect to baseline characteristics, caregivers, compared with non-caregivers, were on average older, more frequently female, married/partnered, frequent alcohol drinkers, current smokers, and exercisers, and they had higher average CCI scores and were less likely to be employed. Caregivers vs. non-caregivers were also more likely to have health insurance, greater education, higher income, and fewer children in the household.

The diagnosis of a terminal or chronic illness can often result in family members being required to provide informal care to patients. Whereas this form of caregiving can have positive effects through benefit-finding and meaning assigned to caring [21–24] across a variety of diseases, it can also be associated with significant burden in physical and psychosocial domains. In the current study, significant burden was identified among individuals providing informal care for those diagnosed with AD or dementia. These findings are aligned with previous studies both in Japan and globally, suggesting that the burden experienced by caregivers extends across geographies, in spite of any influence of individual healthcare systems or cultural differences. Moreover, given little research in Japan investigating this form of burden or exploring its effects on health and economic outcomes, the current study identified potential impact of caregiving not only on quality of life, but also on comorbidities, productivity, and use of healthcare resources.

The caregivers recruited in the current study were on average 52.6 years old, somewhat younger than those involved in other studies of AD (e.g. 63.8 years [45]); however, as in the current study, the majority of caregivers in previous studies were female [45]. The age difference may be representative of the Internet-based format of this study, which may recruit younger individuals more comfortable with the online format.

The current study found that across a majority of health outcome measures, caregivers experienced significantly greater burden than did non-caregivers, even after matching them against non-caregivers with very similar baseline characteristics. Caregivers experienced greater frequency of comorbidities, including depression, insomnia, anxiety, and pain compared with non-caregivers.

Compared with non-caregivers, caregivers reported significantly lower health utilities, nearly reaching the MID for meaningfully poorer HRQoL, and they had significantly poorer physical and mental health status. Similar associations have been reported in the global literature, including among caregivers in the UK and Europe [62–64], thus reinforcing the critical importance of providing support to this vulnerable group.

Further, significant economic consequences were found among study caregivers compared with matched controls. These individuals reported significantly higher work productivity and activity impairment across all metrics. Finally, caregivers reported significantly greater resource use: i.e., more visits to the ER and healthcare providers in the previous six months and more frequent reports of any visit to the ER, hospital, or healthcare providers, further reinforcing the multifaceted economic impact of caregiver burden, as noted in previous studies outside of Japan [25]. With respect to baseline characteristics, caregivers had relatively poorer health and greater comorbid risk than (all, i.e., unmatched) non-caregivers, but they also had more financial resources at their disposal, lack of employment notwithstanding.

The current results align with previous global caregiver studies, including in particular a recent, similar analysis of burden among 209 caregivers of AD patients in NHWS Brazil [33]. For example, relative to their corresponding non-caregiver peers, the Japanese caregivers in the current study experienced health utilities impairments (−0.040 points) comparable to those of the Brazil caregivers (−0.024), as well as comparable impairments on PCS (−1.13 in Japan vs. -0.94 in Brazil) and MCS (−2.60 vs. -1.70, respectively), overall work impairment (26.5 % greater impairment in Japan vs. 35.9 % greater in Brazil), absenteeism (75.3 % vs. 59.6 % greater, respectively), presenteeism-related impairment (23.3 % vs. 32.7 % greater), activity impairment (16.6 % vs. 16.7 % greater), provider visits (43.9 % vs. 28.7 % greater), depression (odds ratio [OR] of 2.0 in Japan vs. 2.0 in Brazil), MDD (OR = 1.8 vs. 1.5, respectively), anxiety (OR = 4.8 vs. 1.7), insomnia (OR = 1.8 vs. 1.6), and pain (OR = 1.5 vs. 1.7).

The impairments found in the current study were also comparable to those reported by caregivers for adult relatives diagnosed with cancer in yet another NHWS-based study in the EU, where health utilities were 0.043 points lower for caregivers vs. non-caregivers (vs. 0.040 points lower for Japanese caregivers in the current study), PCS and MCS were 1.29 and 3.26 points lower, respectively (vs. 1.13 and 2.60 in the current study), overall work impairment, absenteeism, presenteeism-related impairment, and activity impairment were 46, 69, 45, and 32 % greater, respectively (vs. 26 %, 75 %, 23 %, and 17 % greater), provider visits were 33.2 % greater (vs. 43.9 %), and depression, anxiety, and insomnia had ORs = 1.5, 2.0, and 2.0, respectively (vs. 2.0, 4.8, and 1.8) [65].

In yet another NHWS-based study in the US, the burden of caregiving for patients with AD was compared with that for patients with multiple sclerosis (MS), finding that impairments did not differ significantly across the two conditions in terms of work productivity measures, HRQoL, or provider visits, although activity impairment, ER visits, and hospitalizations were significantly greater for caregivers of patients with MS [66].

It is important to note that the comparisons of caregiver burden referenced above are with respect to general health outcomes domains: mental health-related comorbidities, overall mental and physical status, productivity impairments, and resource use. There may be other, more disease-specific variations in burden that were not captured in the current or comparable studies. For example, the specific needs and psychological experiences of caring for individuals with severe dementia or AD may differ from those of caregiving in other conditions, even as general health outcome impairments are similar in degree. Generally, with variations in terms of magnitude and significance of differences across health outcomes, the current study finds that caregivers for patients with AD in Japan experienced impairments comparable to those experienced by caregivers for patients with AD in other geographies (e.g., Brazil and US), as well as impairments experienced by caregivers for patients with other conditions (cancer, MS, and schizophrenia) across geographies [65–67].

Those providing care for patients with dementia (including dementia due to AD) in Japan experience a broad range of care-related burden (physical, psychological, social, and financial), with relatively greater comorbid risk, poorer HRQoL, greater productivity impairment, and higher rates of healthcare resource use. Given aging world populations and corresponding projected increases in AD/dementia diagnoses over time, direct treatment and policies to help caregivers and their patients are needed. Special consideration may need to be given to interventions related to work environments and screening/treatment of depression, given productivity impairments and comorbidities identified among the range of health outcomes assessed in the current study. With Japan’s demographic changes leading to a relatively small workforce supporting the care and financial needs of a growing elderly population, policymakers need to consider the impact of caregiving on many aspects of society. The current study helps to better characterize caregivers in order to help identify where support is most needed. Further research in Japan can help elucidate the broader impact of AD on caregivers and society in general, including assessments of how the caregiver experience is influenced by AD severity and current forms of assistance (e.g., private care and insurance programs), as well as assessments of interventions to assist caregivers.

AD, Alzheimer’s disease; BMI, body mass index; CCI, Charlson comorbidity index; DAT, dementia of the Alzheimer’s type; ER, emergency room; HRQoL, health-related quality of life; MCS, mental component summary; MDD, major depressive disorder; MID, minimally important difference; MMSE, mini-mental state examination; MS, multiple sclerosis; NHWS, National Health and Wellness Survey; OR, odds ratio; PCS, physical component summary; PHQ, patient health questionnaire; SD, standard deviation; SF, short form; WPAI, work productivity and activity impairment.