Search strategy

Due to the extensive number of studies identified within the searched databases and the limited empirical evidence regarding the impact of search and including earlier works on systematic review findings [33], our search strategy covered a publication period from January 2007 and October 2019 within the following databases:

1. MEDLINE (including Medline in Process and other non-indexed citations, ePubs and Medline Daily);
2. Cumulative Index to Nursing and Allied Health Literature (CINAHL);
3. Embase;
4. PsycINFO.

Please refer to the published protocol for details on the data searches and MeSH terms used for each database [31].

Inclusion and exclusion criteria

Given the importance of disaggregating the data by sex and gender when conducting a sex and gender analysis [34], studies included in the review met the following criteria: (1) examine the experiences and/or impacts of caregiving among family caregivers of individuals with any form of dementia; (2) report sex and/or gender distribution of study population and/or report and discuss results stratified by sex and/or gender, and (3) include both male and female family caregivers of persons with dementia. Studies that (1) include both family and formal caregivers but do not stratify findings by caregiver type, (2) do not report results specifically for care recipients with some form of dementia or (3) examine the effects of various interventions on caregiving burden were excluded. Additionally, the following study designs/formats were excluded: case reports or public reports, theses, abstracts, conference materials, editorials and commentaries.

Data extraction: Selection and coding

Two researchers (CX and MB) independently screened study titles and/or abstracts as well as reviewed full texts of manuscripts to determine fulfillment of the inclusion criteria. Discrepancies in opinion were resolved through discussion with a third researcher (AC). A standardized form was used to assess study quality and synthesize study findings from the included studies. Extracted information included the following: (1) author and publication year, (2) study setting and design, (3) study location, (4) information of the study population and demographic characteristics, (5) study results relating to caregiving experiences (i.e. caregiving burden and impacts on physical and/or mental health), (6) details on the methodology used to gather these experiences, (7) the statistical approach used and confounders, (9) information on sex and gender differences and (10) information on the risk of bias assessment. Two reviewers (CX and MB) extracted the data independently and a third reviewer (AC) reviewed the quality of data extraction and mediated a resolution in cases of disagreement through follow-up discussions with the reviewers.

Risk of bias (Quality) assessment

Quality assessment of the studies was conducted independently by two reviewers (CX and MB). Qualitative studies were assessed using the Critical Appraisal Skills Program (CASP) qualitative checklist and consisted of the following steps: (i) assessment of potential sources of bias through a series of 10 questions related to the results, their validity and impact, and (ii) responding to each question as “Yes”, “Cannot Tell” and “No” [35]. Quantitative studies were assessed using the National Institutes of Health (NIH) Quality Assessment Tool for Observational Cohort and Cross-sectional Studies through the following process: (i) assessment of potential sources of bias through a series of 10 criteria applicable to the study, and (ii) grading the presence of potential biases as “Yes” “Cannot Determine”, “No”, “Not Reported” or “Not Applicable” [36]. Following the grading of each study, the overall level of potential bias was summarized: “++” when all or most of the quality criteria were fulfilled and the study classified as “high quality”; “+” when some of the criteria were fulfilled and the study classified as “moderate quality”; “−” when few or no criteria were fulfilled and the study classified as “low quality”. Studies that were classified as “low quality” were excluded from the review.

Data synthesis

The included studies were analyzed using a narrative synthesis approach following the Guidance for Narrative Synthesis in Systematic Reviews [37]. Specifically, textual descriptions, tabulation as well as grouping and clustering were employed in the analyses. Synthesis of the extracted data involved the summarization and explanation of the sex and gender differences for the included studies. In addition, the quality of the included studies was described as part of the narrative synthesis. While a plan was in place to investigate the pooled effect of sex and gender on various aspects of caregiving experiences, the high heterogeneity between the included studies, concerning methodology (statistical methods, type and method of assessment of caregiving experiences), population (age, sex and gender, dementia type, etc.) as well as study settings (country, recruitment locations, etc.) ruled out meta-analysis.

Patient and public involvement

Patients and the public were not involved in this review.

Quantitative studies

Study characteristics.

A summary of the 18 included quantitative studies is presented in Table 1. Of the quantitative studies, all were of a cross-sectional design. With respect to study setting, 15 studies were community-based [38–45, 47–50, 56–58], two were based in the clinic [46, 51] and one was based in both the community and clinic [52]. The type of dementia experienced by the care recipients varied among studies. Seven of the studies included only persons with Alzheimer’s disease; another seven studies included persons with Alzheimer’s disease and other types of dementia such as vascular dementia, Lewy-body disease, frontotemporal dementia among others. The remaining four studies did not report information on the type of dementia.

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Table 1. Findings of all included quantitative studies.

https://doi.org/10.1371/journal.pone.0231848.t001

The 18 quantitative studies reported data from a total of 5735 (range 32–1223) caregivers. All of the studies reported information on sex/gender, and most studies reported the age of participants with the exception of two studies, which did not provide any information on the participants’ ages. The mean age in studies ranged from 53.9 [46] to 77.9 [47] years and the mean age among all reported samples was 66.7 years. The average percentage of men was 33.2% across all samples and the number of women exceeded that of men in all but one study [41]. With respect to caregiving relationships, 13 studies included a mix of children and spousal family caregivers [38–40, 42, 43, 45, 46, 48–52, 57] while five studies focused exclusively on spousal caregivers [41, 44, 47, 56, 58].

Qualitative studies

Study characteristics.

A summary of the four included qualitative studies is presented in Table 2. All of the studies provided information on the sex/gender and age of the participants. All four used semi-structured interviews and were smaller in size, reporting data from a total of 76 caregivers, 42 female and 34 male caregivers respectively. The mean age in studies ranged from 33.6 [53] to 77.6 [54] years and the mean age among all reported samples was 59.5 years. With respect to study setting, two were conducted in a community setting [54, 55], one had a clinical (i.e. tertiary hospital) setting [53] and one was conducted in both clinical and community settings [59]. The type of dementia experienced by the care recipients also varied across the studies. One study included care recipients with Alzheimer’s disease, Parkinson’s dementia or multi-infarct dementia [54]. Another study included care recipients with stage II or III Alzheimer’s disease and related dementia [55]. Finally, one study included care recipients with young-onset frontotemporal lobe dementia [59]. One study did not specify the type of dementia [53].

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Table 2. Findings of all included qualitative studies.

https://doi.org/10.1371/journal.pone.0231848.t002

Sex and gender differences in caregiving burden

Among the 22 studies included in the review, 16 studies examined the sex and gender differences in caregiving burden. This included both formal measures of caregiving burden and semi-structured interviews. Among the 13 studies that used a formal measure to examine the sex and gender differences in caregiving burden, six used the ZBI. Developed more than 30 years ago [62], the ZBI is a reliable and valid caregiving burden instrument most consistently used in dementia caregiving research [63–65]. While all studies that failed to account for confounders found significantly higher levels of caregiving burden among female family caregivers of PWD [39, 45], only half of the studies that did account for confounders (full list shown in Table 1) came to the same conclusion [47, 50]. These contrasting findings highlight the importance of recognizing intersectionality in the context of sex and gender health research. As an analysis approach that moves beyond single or typically favored categories of analysis (e.g. sex, gender, race or class) to consider simultaneous interactions between different aspects of social identity, intersectionality focuses on examining how different socio-demographic factors interact to shape and influence experiences [66, 67]. In the field of caregiving burden, inclusion of these socio-demographic constructs can help to advance understanding of how sex and gender intersects with other dimensions of caregiving. Within this review, a proportion of studies that incorporated additional socio-demographic variables in their analyses and presented an intersectional approach failed to identify significant sex and gender differences, suggesting that these sex and gender distinctions may have been influenced by other socio-demographic factors. As such, these findings call for the adoption of intersectionality plus focus on other social influences in future work on this topic.

Additionally, two studies used the CBI, which like the ZBI, is a scale developed in the late-1980s [68, 69]. The CBI was designed as a diverse, multidimensional and validated instrument to measure the impact of caregiving burden through 24-items selected from a literature review and research [68, 69]. The remaining five studies used the Caregiving Experiences Questionnaire, Pearlin Role Overload Scale, BAS, Pines Burnout Measure and RSS respectively. As most of these scales were developed at a time when caregivers were predominantly female, items within these scales may be inherently gendered and may not adequately reflect the burden and stresses experienced by male caregivers. Moreover, given the myriad of different instruments used by studies to measure caregiving burden, there appears to be a lack of consistency within this topic area, which limits the ability to make comparisons across these studies. As such, future efforts can focus on examining the gendered nature of caregiving burden scales and promoting a level of standardization of the measures used to assess caregiving burden in order to enable meaningful comparisons and knowledge synthesis within this area.

With respect to caregiving burden, findings from the qualitative studies concur with most quantitative studies. Not only did these qualitative studies identify a higher level of stress and challenges faced among female caregivers [53, 54, 59], they also highlighted gendered perspectives that may have contributed to the observed difference between male and female caregivers [54]. Specifically, male caregivers began seeking help earlier and realized the importance of having time to themselves [54]. As such, they were more willing to share some of the caregiving demands and engage in personal activities that provided respite from caregiving. These findings provide a level of insight to the gendered nature of caregiving and its relationship with the observed differences in caregiving burden among male and female caregivers. That said, like most other studies in the review, there was a lack of discussion on the influence of other socio-demographic factors and their role in mediating the relationship between sex, gender and caregiving burden.

Overall, while most of the included studies on caregiving burden demonstrated a higher level of burden among female family caregivers of PWD, these studies often lacked methodological rigor, reflecting the infancy of sex- and gender-based analyses in this area. Specifically, there was a lack of inclusion of other factors that have been shown to influence caregiving burden such as age, time spent on caregiving and dementia severity in the statistical analyses. Given that all but one study are of ‘moderate’ quality, attention should be paid on employing more comprehensive statistical and qualitative methodologies to better tease apart the relationships between sex, gender, as well as other socio-demographic variables and their collective influence on caregiving burden.

Mental health

Among the five studies that examined the prevalence of depression among family caregivers of PWD, female caregivers reported higher scores on instruments such as the CES-D, BDI and GDS compared to their male counterparts. While these findings are in line with the prevalence of depression in the general population where women are almost twice as likely to be diagnosed with depression than men [70], they may not necessarily reflect variations in the caregiving experiences between males and females. As items within traditional depression scales such as sadness and crying are in conflict with societal ideals of masculinity [71], men may be reluctant to endorse these experiences when completing the depression scales. Additionally, there have been suggestions within the current literature that men’s experiences of depression may manifest with symptoms that are not currently included in traditional depression scales [71]. As such, the scales used in the included studies may not capture the true sex and gender disparities that may be present. Furthermore, the lack of consideration of any confounders in most of the studies’ statistical analyses may also limit the applicability and quality of the evidence. Given the recent development of alternative depression scales that take into account different depressive symptoms among male and females [71], future studies can consider examining the validity and reliability of alternative depression scales for uncovering sex and gender differences in depression within the context of informal caregiving.

The studies in this review also investigated other mental health constructs including psychological distress [42, 56], self-esteem [39], family conflicts [42], self-efficacy [42], guilt [43], psychological quality of life [51] and sense of coherence [56]. In particular, significant sex and gender differences were found in all of the constructs with the exception of self-esteem. Despite having a lack of supporting evidence from other studies within the review, the selection of these mental health constructs among studies suggests their relevance within the caregiving context. Specifically, guilt, self-efficacy and self-esteem have all previously been highlighted as themes arising from caregiving experiences, including but not limited to dementia [72–74]. The paucity of studies that have taken on a sex and gender lens when examining these constructs reflect the current emergence of sex- and gender-based analysis in this area. As such, given the significant differences between male and female caregivers, these findings call for a renewed focus of research to further explore the role of sex and gender in this field.

Physical health

Studies on sex and gender differences in caregivers’ physical health focused primarily on comorbidities, sleep, inflammation, and intimacy experiences. Significant sex and gender differences were uncovered in most studies with the exception of intimacy experiences, where contrasting findings were found. A single study highlighted the sex and gender difference in comorbidity among family caregivers of PWD. Utilizing the CCI, female caregivers were found to have less comorbidity compared to males. However, there was a lack of any adjustment for confounders such as age, which had been previously identified as an important adjustment when using the CCI [75, 76]. As such, findings from the study ought to be interpreted with caution and more work is needed in this topic area.

With respect to the impact of caregiving on intimacy experiences among spousal caregivers and their care recipients, studies reported contrasting findings. While the quantitative study that examined intimacy using the Experiences of Intimacy with Partner Scale (EOIPS) found no difference between male and female caregivers [41], interviews conducted by Hayes and colleagues uncovered distinctions in the way male and female spousal caregivers view both their partners and sexual intimacy [55]. Given the sensitive nature of the topic, it is expected that caregivers may not be comfortable disclosing their intimate experiences through an open questionnaire. However, they may be more likely to open up about their perspectives on this issue in a safe and private space during an interview. Moreover, with only 3-items, the valid EOIPS merely quantifies the frequency and level of satisfaction of intimate experiences [41]. As such, it may be unable to capture the nuances of these experiences and thoughts that may have driven the different perspectives in male and female caregivers.

One study examined sleep and found significant sex differences in sleep and its related biomarkers including IL-6 and D-dimer. In contrast with other dimensions examined, male caregivers had worse sleep compared to females after accounting for caregiver age, BMI and care recipient’s dementia severity. Sleep plays important functions with respect to physical and psychological restoration, memory and emotional regulation [77]. Poor quality of sleep has been shown to be one of the main problems facing caregivers and tends to significantly impact their caregiving role [78, 79]. Hence, given the lack of literature on the sex and gender differences in caregivers’ sleep experiences, attention should be paid to engage in deeper investigations on the mechanisms underlying these sex and gender differences in sleep and its relationship with caregiving burden in order to develop effective interventions that will better address such an important physical impact of caregiving.

Limitations

One of the main concerns regarding the included studies was the lack of consistency on the measures used. As such, the estimates provided by each quantitative study were unable to be pooled together and caution is recommended when making inferences. In addition, while socio-demographic variables of the caregivers were extracted, the types of variables are limited to the data collection process of the included studies. As such, certain socio-demographic variables that are known to influence caregiving experiences, such as family income, education level and geographic location may have been omitted by the studies. Moreover, caregiving relationships, which are intricately linked with sex and gender, were not explored in relation to caregiving experiences due to the lack of explicit classifications of the family caregivers in the included studies. Given the limited number of articles retrieved through the systematic search which suggests the overall lack of scholarly focus in this topic area, alternative approaches such as a scoping review may be able to expand the breath of the review to include other caregiving populations.

Given that most of the included studies did not explicitly disentangle sex from gender differences, the review was limited in its ability to report sex and gender findings separately. As such, given the current trend towards disentangling the impacts of sex and gender in understanding male and female differences [80], there is potential for future studies in this field to incorporate a direct gender measure such as the Masculine Gender Role Stress [81] and Bem-Sex-Role-Inventory [82] or construct a gender index based on pre-collected variables. While it is acknowledged that sex and gender interact, these innovative gender measures will enhance our understanding of the relative contribution of sex and gender as individual constructs in differences between male and female caregivers. Finally, this review excluded articles published before 2007, in languages other than English and grey literature. These decisions were made based on the overwhelming number of studies being identified within the databases searched as well as limited empirical evidence about the potential impact of selective searching and inclusion of earlier works on the results of systematic reviews [33]. Despite these limitations, this review aims to enrich science and enhance support provided to family caregivers of PWD by comprehensively pooling together evidence on the sex and gender differences in caregiving burden among family caregivers of PWD.