Impact of Care-Recipient Relationship Type on Quality of Life in Community-Dwelling Older Adults with Dementia and Their Caregivers

Dementia contributes significantly to disability and dependence in older adults. As the global aging population continues to grow, the number of people living with dementia (PLWD) is expected to reach 78 million by 2030. Similarly in Canada, approximately 76,000 new dementia cases are diagnosed annually, and the number of Canadians living with dementia is expected to exceed one million by 2030 and reach 1.7 million by 2050. As a non-curable disease, dementia care research has gradually shifted focus from a disease-modifying treatment or a symptom-focus treatment to prioritize outcomes such as improved quality of life (QoL). This also applies to their informal caregivers, family members and friends, who play a vital role in dementia care. About 61% of PLWD in Canada live in the community and receive care mainly from their informal caregivers. The number of PLWD is projected to nearly triple over 30 years from 2020 to 2050, placing greater demands on Canada’s health care system. Informal caregivers of PLWD dedicate more time and experience higher distress compared to those caring for older adults without dementia. As caregiving demands increase with disease progression, the QoL of informal caregivers is adversely affected, which in turn influences the care quality and subsequently affects the QoL of PLWD. Therefore, enhancing the QoL of PLWD and their informal caregivers warrants attention and is recognized by WHO as a primary goal of dementia research. While the care-recipient relationship type has been reported as an impact factor for QoL of PLWD and caregivers, the existing evidence is limited to single primary caregivers, spouses and adult children, and there needs to be more longitudinal evidence. Research, especially longitudinal studies involving broader typologies of care-recipient relationships and shared caregiving responsibilities, is needed. This thesis comprises three manuscripts that examine the impact of care-recipient relationship type on the QoL among community-dwelling older adults living with dementia (i.e. PLWD) and their informal caregivers cross-sectionally and longitudinally. The selected datasets for this series of secondary analyses, the National Health and Aging Trends Study (NHATS) and National Study of Caregiving (NSOC), allowed us to analyze dyadic data involving a broader range of care-recipient relationship types. NHATS conducts annual in-person interviews with a nationally representative sample of Medicare beneficiaries ages 65 or older, while NSOC conducts periodical phone interviews with informal caregivers of NHATS participants. Together, NHATS and NSOC constitute the only national study providing both care recipient and caregiver perspectives on late-life care. Four types of relationship were identified: (1) care from a spouse/partner; (2) care from an adult child; (3) care from an informal caregiver other than a spouse/partner and adult child, such as child-in-law, sibling, etc. (referred as “other” caregiver); (4) care responsibilities shared by two or more caregivers (referred as “multiple” caregivers). Guided by the International Classification of Functioning, Disability, and Health (ICF) framework and Stress Process Model of Family Caregiving, the QoL of PLWD and their caregivers was assessed through multiple domains, including mental health, general health, functional limitations, and pain for PLWD, and positive emotional benefit, negative emotional burden and social strain for caregivers. PLWD’s dementia status was classified into probable dementia, possible dementia, and no dementia, as suggested by NHATS guidelines. In Manuscript 1, a series of bivariate and multivariable regression models were constructed using data from NHATS (Round 5) and NSOC (II) to investigate cross-sectional associations among relationship types and QoL in PLWD (n=1230) and caregivers (n=1871). The findings revealed that PLWD cared for by an adult-child or “multiple” caregivers exhibited higher functional limitations compared to those cared by a spousal caregiver, even after adjusting for socio-demographic variables (age, sex, race, income, education, marital status, living arrangement) and dementia status. Compared to spousal caregivers, “other” caregivers experienced a lower likelihood of negative emotional burden and social strain, while “multiple” caregivers also demonstrated lower odds of negative emotional burden. When comparing within single caregivers, adult-child caregivers were associated with lower negative emotional burden and higher social strain compared to spousal caregivers. However, when accounting for care recipients’ dementia status, the association between adult-child caregivers and social strain diminished but a significantly higher likelihood of experiencing positive emotional benefit was observed in “other” caregivers. The study highlights variations in both PLWD and caregivers' QoL outcomes based on relationship types, with PLWD's dementia status influencing the association between care-recipient relationship type and caregivers' QoL. In Manuscript 2, a generalized estimating equation (GEE) was performed on data from NHATS Round 5 to 9 to assess the impact of care-recipient relationship type on the changes in PLWD’s QoL over 4 years. The results supported the findings of Manuscript 1, indicating that PLWD cared for by an adult-child or “multiple” caregivers predicted an increased risk of functional limitations both in unadjusted and adjusted models. In addition, there was a significant interaction between relationship type and education. PLWD with high school education or below and cared for by adult-child caregivers experienced a significantly higher risk of increasing functional limitations over the years compared to those with the same education level but cared for by spousal caregivers. Similarly, PLWD who have a high school education and are cared for by “multiple” caregivers exhibited a significantly higher risk of functional limitations than those with the same education level but cared for by spousal caregivers. Manuscript 3 applied GEE on data from NSOC II & III and the companion NHATs Round 5 & 7 datasets. The objectives were to predict the impact of care-recipient relationship type on QoL in caregivers of PLWD over 2 years (2015 to 2017). Results indicated that over time, all three QoL outcomes (positive emotional benefit, negative emotional burden, and social strain) had higher odds of experiencing a high burden compared to the baseline in 2015. Spousal caregivers consistently faced a higher risk of negative emotional burden and social strain than “other” caregivers over time in both unadjusted and adjusted models. This causal relationship aligns with the Manuscript 1 findings and contributes to the overall body of evidence. In addition, adult-child caregivers initially showed a significantly higher risk of social strain over time compared to spousal caregivers, but the significance of this difference diminished after adjusting for socio-demographics and care-recipients’ dementia status. The thesis uses well-organized national companion datasets to contribute to dementia care literature through cross-sectional and longitudinal analyses. It acknowledges the increasing role of “other” caregivers and shared caregiving responsibilities in dementia care, providing longitudinal evidence on QoL changes. It also recognizes the varied needs of PLWD with consideration of socio-demographics and highlights the impact of relationship types on QoL across multiple domains. Additionally, the findings provide insightful practical implications, emphasizing the importance of tailored interventions for specific caregiver subgroups, evaluation of the full spectrum of care demands, and exploration of policies and supportive resources designed for these needs.

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