Cancer is considered as a disease of aging with strikingly higher incidence and mortality rate among aged individuals.1 When an older adult receives a diagnosis of cancer, a family member usually becomes a primary caregiver involving many aspects of care, including dealing with the diagnosis of cancer and treatment decisions, assisting in daily living activities, managing treatment-related adverse effects, and coping with negative emotional feelings. Furthermore, elderly patients commonly present with more comorbidities,2 a higher functional decline and dependence,3 geriatric syndromes,4 and frailty,3,5 which may bring additional challenges to family caregivers. It is well recognized that caring for elderly cancer patients is a complex and stressful task6 that may cause significantly higher caregiver burden.7
Caregiver burden refers to the caregiver perceived physical, emotional, social, and financial hardships as a result of caring for his/her relative.8 Evidence has shown that high caregiver burden may impair caregivers’ physical and psychological health9,10 and decrease their quality of life.11 Given the high prevalence of cancer among aging population and the significant impact of caregiver burden on caregivers’ health, a better understanding of caregiver burden among family caregivers of elderly cancer patients is needed.
Over the past 2 decades, an increasing number of studies have been conducted to measure caregiver burden or to explore multidimensional factors associated with caregiver burden among family caregivers of cancer patients.12–17 Unfortunately, studies focused on family caregivers of elderly cancer patients are still very rare. Given the unique characteristics of elderly cancer patients and challenges faced by their family caregivers, we performed a systematic review to examine the associated factors of higher caregiver burden among family caregivers of elderly cancer patients.
A 3-step search strategy was utilized in this review. An initial limited search of PubMed and CINAHL (Cumulative Index to Nursing and Allied Health Literature) was undertaken followed by analysis of the text words contained in the title and abstract and of the index terms used to describe study. A second search of literature published exclusively in English using the combination of all identified text words and index terms (an example is stated in Table 1) was undertaken across 7 electronic databases including CINAHL, Scopus, PsycINFO, CENTRAL (Cochrane Central Register of Controlled Trials) on The Cochrane Library, Web of Science, MEDLINE, and PubMed from database inception to October 2014. The Boolean/Phrase was applied as a search mode. The search terms were piloted on a sample of studies before being applied. Third, the reference list of all identified studies was searched for any additional studies.
Study Selection and Eligibility Criteria
Original observational studies with assessment of associations between caregiver burden and at least 1 variable using correlation, comparison, or regression analysis were selected. Studies published in English language were considered in this review if they met the following inclusion criteria:
- Types of participants: family caregivers of elderly cancer patients who were providing care at the time of data collection. In this review, we adopted the Department of Statistics Singapore’s classification and took the chronological age of 65 years as a definition of “elderly,”18 which was consistent with most developed countries.19 Elderly cancer patients for this review were treated as a group of cancer patients with a mean or median age of 65 years or older.
- Condition: caregiver burden should be the primary or secondary outcome measured at any course of cancer trajectory, with at least 1 associated factor reported using a validated or nonvalidated instrument.
- Context: in order to have a general understanding of the situation, studies conducted in any setting including homes, hospitals (both inpatients and outpatients), and hospices were considered.
A study was excluded if it met any of the following criteria:
- Results were not presented separately for family caregivers of cancer patients.
- Patient’s age was not available or patients’ mean/median age was younger than 65 years.
- The study shared the same sample with another major study that was included in the review.
- Caregiver burden was an independent variable instead of an outcome.
After eliminating all the duplicate studies, articles were assessed based on title and abstract for eligibility against the inclusion and exclusion criteria mentioned previously. Full texts were obtained and assessed by 2 reviewers independently. Studies not fulfilling the inclusion criteria were excluded after noting down the reason for exclusion. Disagreements between the reviewers on inclusion/exclusion of studies were resolved by discussion. All the identified references were stored in Endnote software version X7.2. [Thomson Reuters (Scientific) LLC, Philadelphia, PA].
The methodology quality of the included studies was independently assessed by 2 reviewers using a modified checklist adapted from Duckitt and Harrington20 and Zhao et al.21 The checklist contains 5 items to be assessed by 9 individual criteria (Table 2). Disagreements in quality assessments were resolved through discussion. Zero point was assigned if the study did not meet the criterion. The quality score was calculated by summing up all the individual item scores. Based on the criteria, studies could receive up to 9 points. Included studies were further classified into high, moderate, or low quality (Table 3) based on their methodological quality score. None of the studies were excluded based on the quality assessment results.
Data Collection and Extraction
A data extraction form was developed to extract key information from the relevant studies. The information extracted included study characteristics (ie, authors, publication year, country, study design, and sample size), the profile of family caregivers (ie, age, gender, and relationship to patient), the clinical characteristics of elderly cancer patients (ie, cancer diagnosis, cancer stage, and course of cancer), and caregiver burden–related information (ie, the instrument used, prevalence and scores of caregiver burden, and identified factors associated with caregiver burden).
The included studies were heterogeneous in terms of caregiver burden measures used, factors explored, and different analyses applied; a narrative synthesis of study findings was performed. The study design and sample characteristics were described. The prevalence and severity of caregiver burden were briefly summarized. The extracted factors were categorized with their corresponding level of evidence rated using the “best-evidence synthesis” model,22 which were increasingly used by systematic reviews.21,23–25 “Strong evidence” means that further study is very unlikely to change our confidence in the estimate of effect. “Moderate evidence” means that further research is likely to have an impact on our confidence in the estimate of the effect and may change the results. “Limited evidence” means that further research is very likely to change the results. “Conflicting evidence” means that any estimate of effect is very uncertain. “No evidence” means that no statistically analyzed or discussed factors are presented.
Identification of Relevant Studies
The initial literature search of 7 databases identified 2181 studies after removing 1158 duplications. After title and abstract screening, 537 studies were selected for full-text assessment. Studies that did not have available full text (n = 1), did not meet the inclusion criteria (n = 420), did not present results separately for family caregivers of elderly cancer patients (n = 9), did not present patient’s age or involved younger cancer patients (n = 94), shared same sample with another included study (n = 1), and measured caregiver burden as an independent variable (n = 5) were excluded (Figure). Finally, 7 studies were included in the review.
Quality of Studies
Of the 7 included studies, 3 studies (42.9%) had a quality score of 7 and were assessed to be high-quality studies, 2 studies (28.5%) had a quality score of 6 and were rated as moderate quality studies, and 2 studies (1 study each [14.3%]), which had a quality score of 5 and 4, respectively, were low-quality studies (Table 4).
Of the included studies, 4 were conducted in the United States26,29,30,32 and one each in Israel,28 Italy,31 and Thailand,27 respectively. All the reviewed studies had been published since 1999, with 5 published since 2007 (Table 5).
These 7 studies involved 1233 eligible family caregivers (range, 30–618 eligible family caregivers). They were predominantly females (approximately 75.3%). The majority of the family caregivers were spouses (average, 65.9%; range, 26%27 to 100%28). They provided primary care to cancer patients during or after cancer treatment in 5 studies and during hospice or inpatient palliative care in 2 studies. Patients all received a diagnosis of 1 type of cancer (lung cancer32 or colorectal cancer31) in 2 studies and presented with different types of cancer in the other 5 studies.
Prevalence and Severity of Caregiver Burden
Caregiver burden was measured using 5 different validated measures including Caregiver Strain Index,26,32 Caregiver Reaction Assessment and its subscales,29,30 Zarit Burden Inventory 29-item original version28 and 22-item revised version,27 and Caregiver Burden Index.31
The prevalence of caregiver burden in family caregivers was not reported in the majority of the studies.28,30–32 Based on the 3 studies with prevalence data reported, the proportion of family caregivers who reported certain level of caregiver burden varied from 37%27 to 100%.29
Mild to moderate caregiver burden was generally reported by family caregivers.26,27,29,31 The percentage of caregivers who reported high burden ranged from 1%27 to greater than 35%.31
Associated Factors of Caregiver Burden
Twenty-two factors were identified to be associated with higher caregiver burden (Table 6). They were analyzed and grouped into 4 categories: caregiver characteristics, patient characteristics, caregiving situation, and supporting resources based on existing stress-process models of family caregiving.30,33
The examined caregiver characteristics that were associated with higher caregiver burden included sociodemographics (ie, younger age, male sex, nonwhite, single, primary or lower education, and being employed), presence of migraine or anxiety disorder, a lower score of quality of life, relationship to patient, and a lower score of self-efficacy.
Moderate evidence showed that younger age was a significant factor associated with higher caregiver burden.26,28,31 The association between relationship to patient and higher caregiver burden was reported in 2 studies with contradictory findings: siblings reported higher caregiver burden in a high-quality study,27 whereas spouses and children in a moderate-quality study.31 The evidence of the association between the other 9 caregiver characteristics factors and higher caregiver burden was still limited because it was supported by only 1 high- or moderate-quality study (Table 6).
The identified patient characteristics associated with higher caregiver burden included a lower score of physical function, unintentional weight loss of 5% or greater, presence of musculoskeletal disorder, high symptom or psychological distress, limitations in social activities, cancer type, and a lower score of self-efficacy.
Moderate evidence supported that cancer type was significantly associated with higher caregiver burden.26,27 Family caregivers of patients with solid tumors (especially nonbreast solid tumors) experienced caregiver burden. The evidence of the association between the other 6 patient characteristics factors and higher caregiver burden was also limited (Table 6).
Overall, the association between caregiving situation and caregiver burden was not well explored in the reviewed studies. The identified caregiving situation factors included assistance with activities of daily living and caregiving time. Assistance with activities of daily living, a factor supported by moderate evidence, was consistently identified to be associated with higher caregiver burden.26,27 The evidence supporting the association between caregiving time of 10h/wk or more and higher caregiver burden was limited.
The association between supporting resources and caregiver burden was scarcely examined in the reviewed studies. Limited evidence supported that lack of social support26 and insufficient financial support27 were factors contributing to higher caregiver burden.
Although caring for cancer patients is considered as shorter duration compared with caring for patients with mental diseases, it is well documented in literature that family caregivers experienced equivalent levels of burden to what caregivers of dementia did.34,35 This systematic review summarized the factors associated with higher caregiver burden in diverse settings worldwide. The evaluation of current evidence identified 3 moderate-evidence factors associated with higher caregiver burden: younger caregivers, solid tumors, and assistance with the patient’s activities of daily living. The findings of younger caregivers reporting higher caregiver burden were consistent with other studies demonstrating that younger caregivers experienced more psychological distress induced by caregiving36,37 because their activities might be more restricted and their financial status might be less secure than older caregivers.37,38 Assistance with patient’s activities of daily living was also consistently identified as a significant individual factor contributing to higher caregiver burden by other studies regardless of the disease of patients.39–41 This could be explained in that providing assistance with patient’s activities of daily living requires increased number of hours devoted to caregiving and a higher level of caregiver engagement.41
Because of the paucity of primary studies of caregiver burden among family caregivers of elderly cancer patients and the high degree of variability in terms of factors investigated, many of the factors associated with higher burden were found to be limited evidence, which was supported by only 1 reviewed study. Some of these factors such as caregivers being single, with primary or lower education or being employed, providing care to patients with decreased physical function, or high symptom or psychological distress were also supported by other caregiver studies.42–46
Although many studies suggested that female caregivers (not limited to caregivers of elderly cancer patients) experienced higher caregiver burden than did male caregivers,42–44 hypothesizing that women experience consequences of caregiving due to their typical engagement in more personal care than men in the caregiver role,47 limited evidence in this review indicated that male caregivers of elderly cancer patients reported higher caregiver burden. This probably could be explained by the cultural norms and the unique challenges and difficulties encountered by males when they have to take on the caregiving role that they are less socially prepared for. As the proportion of male caregivers keeps increasing, more studies are needed to understand male caregivers’ experiences further.
Although relationship of caregiver to patient was well established as an influencing factor of caregiver burden, it should be explored further among family caregivers of elderly cancer patients as controversial effect was observed in the reviewed studies.
As the use of different caregiver burden measures in different studies makes comparison of caregiver burden among studies impossible, we were unable to do any further analysis to identify whether cancer stage or course of cancer was an associated factor of high caregiver burden. Because of the above heterogeneities among the studies, it was impossible to pool data for meta-analysis and to determine the estimates of the effects of individual factors. As the “best-evidence synthesis” method is a useful method for making a clinical recommendation,22 the results of this systematic review should be considered as valid.
It was possible that some eligible articles were missed in this review because articles published in languages other than English were not included, which might introduce language bias. This systematic review included only observational studies. Although observational studies are the most commonly used design for caregiver burden research, it is acknowledged that observational studies are sensitive to sample selection, detection, classification, and confounders.48 As the majority of caregiver burden measures lack either theoretically or empirically defined threshold for high burden, if the cutoff score for high burden used by the studies was not appropriate, it might affect the examination of associated factors. The variations in the population of caregivers and patients studied, methodology, instruments used, and cultural norms may cause differences in factor identification in individual studies. Despite that the criteria of methodological quality assessment had been used in this systematic review, low-quality studies were not excluded in view of the very finite number of studies included. All these considerations should be taken into account when interpreting the findings.
As most of the reviewed studies were conducted in western countries, because of the differences in social patterns, culture, value, and family structure between western countries and Asian countries, as well as the differences in burden of cancer, the findings might not thoroughly reflect caregiver situation in Asian countries.
This systematic review provided a summary of factors associated with higher caregiver burden among family caregivers of elderly cancer patients. Twenty-two factors were identified to be associated with higher caregiver burden, of which 3 were supported by moderate evidence, 18 were supported by limited evidence, and 1 was a conflicting factor. In general, family caregivers who were at a younger age, caring for solid tumor patients, and providing assistance with patient’s activities of daily living tended to experience higher caregiver burden. The association between relationship of caregiver to patient and higher caregiver burden was still very uncertain.
Implications to Clinical Practice and Research
It is important to identify factors contributing to higher burden on family caregivers of older adults with cancer to target interventions at family caregivers most in need and reduce adverse health outcomes related to caregiver burden. The associated factors examined by this systematic review might provide evidence in identifying family caregivers at high risk of high caregiver burden. More high-quality studies with confounding factors identified and appropriate strategies applied are highly needed to clarify and determine the estimates of the effects of individual factors.
The authors thank Drs Nakul Saxena and Pradeep Paul George Gunapal from Health Services and Outcomes Research Department, National Healthcare Group, for the comments given on the manuscript of this study.
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