This is the first study to directly examine the association of RC between the CR and the care provider, as reported by caregivers, with subsequent rate of cognitive and functional decline in CRs with AD. With closer relationships, participants declined more slowly in cognition and functional capacity, even after adjustment for several potential confounders. These findings were stronger when caregivers were the spouses of the participants with AD. Furthermore, effects observed in the present study were on the same order of magnitude as reported in a recent meta-analysis of nine clinical trials using acetylcholinesterase inhibitors (AChEIs; Birks, 2006
). Averaging across the nine studies, mean difference in MMSE score between those treated with AChEIs versus placebo was 1.37 MMSE points annual change (95% CI = 1.13–1.61) measured over an interval ranging from 6 to 12 months. Our findings of 0.72- and 1.16-point differences in annual rate of change of MMSE (for effect of closer relationships and spouse caregivers, respectively) are promising. They suggest that interventions enhancing the caregiving dyadic relationship, including those already developed to improve care management strategies (Logsdon, McCurry, Moore, & Teri, 1997
), would slow the progression of dementia.
The slower rates of cognitive and functional decline in those with AD who have spouse caregivers suggest a particular importance of marital relationships in dementia care. Persons with dementia and their spouses are noted to be “living in relationship” (Davies & Gregory, 2007
) with shared meanings continuously cocreated by the couple (Graham & Bassett, 2006
). Older married couples in our sample are probably typical of such couples elsewhere in their shared long-term commitment to mutual assistance through adversity (the duration of their marriages averaged 51.3 years, SD
= 16.6). Interdependence theory and the investment model support the notion that such commitment makes spouses more willing to accept a caregiving role and sacrifice self-interest than adult children, who must balance parent care responsibilities with responsibilities to other family members, including spouses and children (Piercy, 1998
). The need for such a balance may explain why adult child and spouse caregivers reported similarly moderate stress levels despite the fact that coresidency was more common for spouse than adult child caregivers.
Although caregiver–CR relationships have developed over the lifetime of the marriage (for spouse caregivers) or child (for adult child caregivers), work done by Kitwood (1990
and Graham and Bassett (2006)
affirm the dynamic nature of dyadic relationships, thus suggesting their potential for change through intervention, even in the late stages of a relationship.
Because commitment to and investment in the relationship with the CR are likely to be important to the success of dyadic interventions in dementia caregiving, interventions that focus on collaborative aspects of care dyads have shown promise in improving these relationships. Quayhagen and Quayhagen's (1996)
4-month cognitive remediation intervention improved spouse relationships as dyads rediscovered life quality. More recently, a counselor-guided dyadic intervention for family caregivers and persons with early-stage dementia designed to help care partners (including non–spouse caregivers) plan for future care needs showed success in attaining concrete plans (Whitlatch, Judge, Zarit, & Femia, 2006
). Critical to the success of this intervention was a sense that persons with dementia felt listened to and understood by their caregivers.
One way in which closer relationships might predict improved outcomes is their tendency toward more successful and adaptive care management strategies. For example, engagement of persons with AD in cognitively and socially stimulating activities (Graham & Bassett, 2006
) may in turn slow the rate of cognitive decline (Quayhagen & Quayhagen, 1996
; Quayhagen & Quayhagen, 2001
). We also note, however, that caregivers in our sample who reported higher levels of closeness also described greater use of services such as respite care, meal delivery, housekeeping, and so forth (data not shown)—any or all of which might lessen the daily demands of caregiving and allow more time for the pair to share meaningful activities. Respected service providers may also teach caregivers to become more skillful at care provision (Piercy & Dunkley, 2004
Among this study's strengths is its use of a population-based sample, often more representative than clinic-based samples with higher occupational and educational status and younger onset of AD (Kokmen, Ozsarfati, Beard, O'Brien, & Rocca, 1996
). Other strengths include a detailed and standardized diagnostic workup of the participants with new-onset AD, a high enrollment rate, and a longitudinal design with semi-annual visits.
An important limitation of this work is the brevity and simplicity of the RC instrument, which was included among many other measures used in the CC-DPS. The six-item instrument was originally designed for studying adjustment to nursing home placement (Whitlatch et al., 2001
). Notwithstanding its apparent face validity, this scale has not specifically been validated for measurement of such important variables as communication quality, mutual respect, empathy, and affection. Furthermore, given the nature of the sample, we cannot assess the extent to which the participants'
perceptions of RC might be predictive of clinical course. Seventy-five percent of caregivers were female (45 wives, 81 daughters/daughters-in-law), as is typically the case with dementia caregiving. We therefore did not have sufficient numbers to be able to stratify analyses by all combinations of spouse versus adult child caregiver type, gender of caregiver, and gender of CR. Thus, the study of differential effects of these eight combinations awaits further data collection, with results presented here somewhat more generalizable to dyads with female caregivers. Finally, our findings may be relatively specific to mild-to-moderate AD. Additional years of follow-up will be needed to learn whether the effects reported here appear only in the mild and moderate stages of AD or whether they will remain important as symptoms progress.
In this population-based study of AD progression, a closer caregiving relationship was associated with slower progression of cognitive and functional symptoms, particularly for persons with spouse caregivers. Although caution is warranted because the direction of effect may be one in which slower cognitive or functional decline promotes closer relationships, findings were robust after control for dementia severity, raising questions about caregiver strategies that may promote better functioning in dementia. Furthermore, although our measure of functional status was not entirely independent of the caregiver (and therefore the caregiver's RC report), the consistency of our results across both the functional and the objectively measured cognitive domains lends further support to them.
It is conceivable that RC may reflect caregiver strategies that flexibly adapt to the needs of the person with AD, encouraging, when appropriate, participation in cognitively and socially stimulating activities, which help promote sustained functioning. Conversely, less close caregivers may experience more negative stress from the burden of care provision to a person with whom they feel more distant, especially if the caregiver has little understanding of what to expect as dementia progresses. Furthermore, persons cared for by more stressed caregivers may be at greater risk of behavioral neuropsychiatric symptoms; this may result in increased use of psychotropic medications or interfere with treatment of comorbid medical conditions and thereby accelerate decline. Additional studies can help to clarify if RC is a marker for caregiver personality, stress, burden, interdependence with CR, care management strategies, or other factors that affect clinical course of dementia. Such factors could be targets of future interventions designed to enhance the caregiving dyadic relationship in an effort to slow decline in AD.