Norton, M.C. , Piercy, K.W. , Rabins, P.V. , Green, R.C. , Breitner, J.C.S. , Østbye, T., Corcoran, C., Welsh-Bohmer, K.A. , Lyketsos, C.G. , & Tschanz, J.T. (2009). Caregiver – recipient closeness and symptom
progression in alzheimer disease. The cache county dementia progression study. Journal of Gerontology: Psychological Sciences, 64B(5), 560–568, doi:10.1093/geronb/gbp052. Advance Access publication
on June 29, 2009.
© The Author 2009. Published by Oxford University Press on behalf of The Gerontological Society of America.
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lion cases projected by the year 2050 in the United States
alone ( Alzheimer ’ s Association, 2008 ). Strong efforts have
been made to identify factors that might delay or prevent
its onset. These factors include several potentially disease-
modifying interventions intended to modify cleavage of
the amyloid precursor protein or to control the hyperphos-
phorylation of tau, infl ammation, oxidation, or excitotox-
icity ( Salloway, Mintzer, Weiner, & Cummings, 2008 ).
Less thoroughly studied are nonpharmacological factors
such as caregiving environment or practices that may delay
the progression of symptoms in AD.
Estimates from clinic-based studies suggest that the
cognitive abilities of persons with AD decline by 0.8 – 4.4
points per year on the Mini-Mental State Exam (MMSE),
with the typical decline of about 3 points per year ( Behl,
Stefurak, & Black, 2005 ). Two population-based studies
have reported decline rates of 2.3 – 2.9 MMSE points per
year ( Aguero-Torres, Fratiglioni, Guo, Viitanen, & Winblad,
1998 ; Slooter et al., 1999 ), and we recently published a
LZHEIMER ’ S dementia (AD) remains a major pub-
lic health problem, with a prevalence of 11 – 16 mil-
mean decline of 1.9 (95% CI = 1.7 – 2.1) MMSE points
per year in persons with newly diagnosed AD from the
population of Cache County, Utah ( Mielke et al., 2007 ).
More rapid decline has been associated with higher educa-
tion in some ( Stern, Albert, Tang, & Tsai, 1999 ; Teri,
McCurry, Edland, Kukull, & Larson, 1995 ) but not all
( Bowler, Munoz, Merskey, & Hachinski, 1998 ; Regan
et al., 2006 ; Small, Viitanen, Winblad, & Backman, 1997 )
samples. Similarly, more rapid decline has been reported
in the presence of comorbid medical conditions, especially
vascular risk factors ( Mielke et al., 2007 ) and with younger
onset age in some ( Teri et al., 1995 ; Lucca, Comelli,
Tettamanti, Tiraboschi, & Spagnoli, 1993 ) but not all
( Bowler et al., 1998 ; Small et al., 1997 ; R. G. Stern et al., 1994 )
Studies. Finally, more rapid cognitive decline has also been
associated with baseline behavioral disturbances such as
agitation and psychosis ( Scarmeas et al., 2005 ; Y. Stern
et al., 1994 ). Thus, there is evidence that education, co-
morbid medical conditions — in particular, vascular health
conditions — and behavioral disturbances are important
moderators of decline in AD.
Caregiver – Recipient Closeness and Symptom Progression
in Alzheimer Disease. The Cache County Dementia
Maria C. Norton , 1 , 2 , 3 Kathleen W. Piercy , 1 , 3 Peter V. Rabins , 4 Robert C. Green , 5 , 6 , 7 John C. S. Breitner , 8 , 9
Truls Østbye , 10 Christopher Corcoran , 3 , 11 Kathleen A. Welsh-Bohmer , 12 , 13
Constantine G. Lyketsos , 4 , * and JoAnn T. Tschanz 2 , 3 , *
1 Department of Family, Consumer and Human Development , 2 Department of Psychology , and 3 Center for Epidemiologic Studies,
Utah State University, Logan .
4 Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland .
5 Department of Neurology , and 6 Department of Medicine (Genetics), Boston University School of Medicine, Massachusetts .
7 Department of Epidemiology, Boston University School of Public Health, Massachusetts .
8 VA Puget Sound Health Care System, Seattle, Washington .
9 Department of Psychiatry and Behavioral Sciences, University of Washington School of Medicine, Seattle .
10 Department of Community and Family Medicine, Duke University Medical Center, Durham, North Carolina .
11 Department of Mathematics and Statistics, Utah State University, Logan .
12 Department of Psychiatry and Behavioral Sciences , and 13 Bryan Alzheimer ’ s Disease Research Center, Duke University Medical
Center, Durham, North Carolina .
Applying Rusbult ’ s investment model of dyadic relationships, we examined the effect of caregiver – care recipient
relationship closeness (RC) on cognitive and functional decline in Alzheimer ’ s disease. After diagnosis, 167 par-
ticipants completed up to six visits, observed over an average of 20 months. Participants were 64% women, had a
mean age of 86 years, and mean dementia duration of 4 years. Caregiver-rated closeness was measured using a
six-item scale. In mixed models adjusted for dementia severity, dyads with higher levels of closeness ( p < .05) and
with spouse caregivers ( p = .01) had slower cognitive decline. Effect of higher RC on functional decline was greater
with spouse caregivers ( p = .007). These fi ndings of attenuated Alzheimer ’ s dementia (AD) decline with closer re-
lationships, particularly with spouse caregivers, are consistent with investment theory. Future interventions de-
signed to enhance the caregiving dyadic relationship may help slow decline in AD.
Key Words: Alzheimer ’ s disease — Caregiving — Interpersonal relations .
by guest on October 29, 2015
CAREGIVER CLOSENESS AND AD SYMPTOM PROGRESSION
Although several studies have examined the effects of
the clinical features of dementia on caregiver well-being
( Gaugler, Davey, Pearlin, & Zarit, 2000 ; Ory, Hoffman, Yee,
Tennstedt, & Schulz, 1999 ), little is known about the extent
to which decline in dementia is modifi ed by the care envi-
ronment. Kitwood (1993) has argued that dementia caregiv-
ing is a “ cooperative and reciprocal engagement ” (pp.
64 – 65) that requires a caregiver to be emotionally available
to the care recipient (CR), have high levels of empathy and
imagination, and engage in fl exible thinking. This approach
posits that acceptance of the validity of CRs ’ experiences
and accurate identifi cation of their needs are crucial to de-
velopment of a positive care environment. This hypothesis
is supported by studies demonstrating that “ nonadapting ”
(nonacceptance) strategies appear to predict worse out-
comes than “ supporting ” strategies (adapting to the CR ’ s
level; de Vugt et al., 2004 ), and a longitudinal study of spou-
sal dementia care demonstrating that positive spousal inter-
actions, high caregiver commitment, good caregiver health,
and shorter caregiving duration were all associated with de-
layed nursing home placement in dementia ( Wright, 1994 ).
Support for the hypothesis that the care environment infl u-
ences the progression of dementia symptoms is provided
by clinical trial fi ndings that caregiver interventions in-
tended to stimulate cognitive abilities in dementia patients
may also attenuate their cognitive decline ( Quayhagen &
Quayhagen, 2001 ), improve the quality of life for both care-
givers and their CRs ( Quayhagen & Quayhagen, 1996 ), and
delay nursing home placement ( Mittelman, Haley, Clay, &
Roth, 2006 ).
Several studies have examined the association of care-
giver and CR relationships and selected outcomes. Closer
perceived relationships are associated with better adjust-
ment to nursing home placement in persons with dementia
( Whitlatch, Schur, Noelker, Ejaz, & Looman, 2001 ) and
improved psychological well-being and problem-solving
abilities ( Burgener & Twigg, 2002 ). Conversely, avoid-
ance by caregivers or insecure attachment styles in their
CRs have been associated with more behavioral problems
in the latter ( Perren, Schmid, Herrmann, & Wettstein,
2007 ). Graham and Bassett ’ s (2006) longitudinal ethno-
graphic study of persons with Alzheimer ’ s disease and
their family caregivers presents strong evidence that car-
ing relationships are “ dynamic co-constructions built
upon everyday events, interactions, environments, and
disease progression ” (p. 335). In their study, cooperative
care relationships were built on foundations of mutual
respect and sensitivity to persons with dementia, whereas
lack of trust and compassion leads to unrealistic expecta-
tions and negative reciprocity. In the current study, we
used interdependence theory ( Kelley & Thibaut, 1978 )
and the investment model of commitment ( Rusbult &
Buunk, 1993 ) to guide development of hypotheses. For-
mulated to explain behavior in dyadic relationships, inter-
dependence theory holds that relationship partners become
interdependent over time through their interactions. As in-
terdependence increases, so does concern for the partner ’ s
outcomes, and a transformation of motives occurs from
motives of self-interest to prorelationship motives ( Lewis
et al., 2006 ). The investment model suggests that interde-
pendence is felt as commitment, characterized by desire
to maintain the relationship through good and bad times
( Rusbult & Buunk, 1993 ). To that end, investments are
made, including sacrifi ce for one ’ s partner. Using these
theories, and the signifi cant association between positive
spousal interactions, high caregiver commitment, and fa-
vorable outcomes in persons with dementia noted previ-
ously ( Wright, 1994 ), we would expect relationships
between AD caregivers and their CRs characterized as
close to result in more favorable cognitive and functional
Given the evidence that aspects of the care environment
are associated with more favorable outcomes in dementia,
we examined whether rate of progression of dementia is in-
fl uenced by type of relationship (spouse vs adult child) and
caregiver – CR relationship closeness (RC) in a population-
based sample of persons with AD. We hypothesized that
CRs with spouse caregivers, and those whose caregiver
rated their relationship as closer, would experience slower
rates of cognitive and functional decline.
The Cache County Dementia Progression Study (CC-DPS)
is one of few population-based studies of dementia progres-
sion in an incidence cohort, examining longitudinal cogni-
tive, functional, and behavioral outcomes and the factors
that may modify their course. Individuals were enrolled in
the CC-DPS between 2002 and 2004 after fi rst being diag-
nosed between 1998 and 2002 with new- onset dementia in
the Cache County Memory Study (CCMS), a longitudinal
population-based study of dementia that has now completed
four triennial “ waves ” of dementia ascertainment using a
multistage case detection protocol ( Breitner et al., 1999 ;
Miech et al., 2002 ). The CCMS has identifi ed 357 prevalent
and 473 new-onset (after baseline) cases of dementia.
Since the start of the CC-DPS in 2002, 241 individuals
(87% of those still living when recruited for CC-DPS) diag-
nosed in the parent study with new-onset dementia, along
with their principal caregivers, were enrolled. Among this
panel, 183 (75.9%) had been diagnosed by a clinical review
panel with possible or probable AD according to the National
Institute of Neurological and communicative Disorders and
Stroke and the Alzheimer’s Disease and Related Disorders
Association (NINCSA-ADRDA) criteria ( McKhann et al.,
1984 ). Of these, we excluded nine persons with dementia who
had caregivers other than spouses or adult children, two missing
relationship type, and fi ve whose caregiver did not complete
by guest on October 29, 2015
NORTON ET AL.
the closeness measure, for a fi nal sample size of 167 per-
sons with AD and their caregivers.
Participants with AD were 64% female, 99% Cauca-
sian, with mean age of 86.4 ( SD = 5.7) years, mean educa-
tion of 13.2 ( SD = 3.0) years, and mean dementia duration
of 4.0 ( SD = 2.0) years. At enrollment visit, 20 partici-
pants (12%) were living in a skilled nursing facility (SNF),
37 (22%) in residential or assisted living facility (ALF),
and the remainder at home (or caregiver ’ s home). Over the
subsequent observations (almost 2 years, on average), 7
participants moved into an SNF and 15 moved into an
ALF; however, the association between baseline closeness
level and subsequent move to either SNF or ALF was non-
signifi cant ( c 2 = 2.93, df = 4, p = .570). The fi nal sample
of 167 persons with AD comprised 63 male CRs whose
caregivers were wife ( n = 45), daughter or daughter-in-law
( n = 12), or son or son-in-law ( n = 6) and 104 female CRs
whose caregivers were husband ( n = 18), daughter or
daughter-in-law ( n = 69), or son or son-in-law ( n = 17).
Participants were observed for a mean of 20.3 ( SD = 13.0)
months and 49% coresided with their caregiver. Caregiv-
ers were 77% female with 43% spouses and 57% adult
children, mean age of 65.2 ( SD = 14.9) years, mean educa-
tion of 14.3 ( SD = 2.5) years, and mean length of caregiv-
ing of 3.8 ( SD = 4.6) years.
After enrollment, participants were examined every 6
months at their place of residence and observed for 4 – 51
months ( M = 20.3, SD = 13.0 months). Of the 167 who com-
pleted the enrollment visit, there were 129 with at least two
visits, 80 with at least three visits, 50 with at least four visits,
28 with at least fi ve visits, and 21 with at least six visits .
The examinations included manometric measurement of
blood pressure, a brief neurological exam, an inventory of
functional status, and administration of a brief ( ~ 45 min)
neuropsychological test battery. At each visit, caregivers
were also asked about the caregiving environment, as de-
scribed subsequently. Written informed consent was ob-
tained for each interview. All procedures were approved by
the institutional review boards of Utah State University and
the Johns Hopkins University.
Exposure Measurement: RC
Closeness of the caregiving relationship was measured
using a six-item instrument developed by Noelker (1996)
and Whitlach et al. (2001) . This Relationship Closeness
Scale (RCS) used 4-point Likert scale responses that cap-
tured caregivers ’ degree of agreement with six statements
about their relationship with the individual for whom they
provided care. The six statements were presented twice,
once soliciting responses with respect to their current re-
lationship and once with respect to the relationship “ prior
to the time when you began to provide care to him/her. ”
Correlation between assessments of current versus prior
RC was r = .628 ( p < .001). Only the responses assessing
their current relationship were used in this study. Total
scores (range: 6 – 24) were calculated by summing the
scores on the six individual items. Higher values on the
RCS indicated closer relationships. This measure was col-
lected at enrollment into the dementia progression study
Outcomes: Cognitive and Functional Progression in AD
Symptom progression was assessed every 6 months us-
ing standard measures administered by specially trained
neuropsychological technicians and research nurses. The
assessment included the Consortium to Establish a Regis-
try for Alzheimer’s Disease adaptation of the MMSE
( Morris et al., 1993 ), a 30-point cognitive screening test
that includes 10 items on orientation, a brief test of im-
mediate and delayed recall, as well as varied items assess-
ing language, and praxis. When three or fewer points were
missed owing to sensory impairments, we adjusted scores
by extrapolating the proportion of items answered cor-
rectly over a total of 30 points. For individuals who had
progressed to advanced dementia, the technician attempted
to administer the test according to standard instructions.
However, in a few instances (one testing session for 10
participants, two testing sessions for 5 participants, and
three testing sessions for 1 participant), the technician dis-
continued test administration due to poor comprehension.
In such instances, we summed across the items attempted
to obtain a total score.
Progression of functional impairment was measured us-
ing the “ sum of boxes ” score on the Clinical Dementia
Rating (CDR; Hughes, Berg, Danziger, Coben, & Martin,
1982 ). Individual item ratings were made by the nurse af-
ter the examination and a clinical interview with the care-
giver. Individual item scores (boxes) were endorsed after
comparing the participant ’ s abilities with standard text de-
scriptions of six different levels of severity ranging from 0
( no impairment ) to 5 ( total loss of function ). The six indi-
vidual CDR items assess memory, orientation, problem
solving and community involvement, and functional abili-
ties at home and in personal affairs (CDR range: 0 – 30). In
assigning the individual CDR item scores, the research
nurse incorporated caregiver report and his or her own
clinical observations during interaction with the partici-
pant while conducting the neurological examination. The
nurse additionally incorporated ongoing knowledge of the
individual participant ’ s dementia progression from having
consistently visited the participant every 6 months over
several years. Furthermore, in cases where the caregiver ’ s
report was clearly incongruent with the nurse ’ s clinical ob-
servations, an additional assessment was sought by inter-
viewing another knowledgeable informant, where available.
by guest on October 29, 2015
CAREGIVER CLOSENESS AND AD SYMPTOM PROGRESSION
Thus, although caregiver burden or stress or poor RC may
infl uence the caregiver ’ s assessment of the participant ’ s
functional status (making these measures not entirely
independent), a great deal of clinical judgment by the nurse
also entered into the fi nal CDR ratings.
Neuropsychiatric disturbance was evaluated by the nurses
using the ten-item version of the Neuropsychiatric Inventory
( Cummings, et al. 1994 ) that assesses delusions, hallucina-
tions, dysphoria, anxiety, agitation or aggression, euphoria,
disinhibition, irritability or lability, apathy, and aberrant mo-
tor activity. Symptoms not endorsed are assigned a score of
0, and each endorsed symptom is rated on frequency from
1 ( occasionally ) to 4 ( very frequently ) and on severity from
1 ( mild ) to 3 ( marked ). A composite neuropsychiatric distur-
bance score (range: 0 – 120) then sums the product of Fre-
quency × Severity ratings across the 10 domains.
Contextual factors describing the caregiving environment
assessed whether the participant with AD resided at home
or coresided with the caregiver and whether anyone else as-
sisted the caregiver with provision of care. The use of for-
mal or informal services by the caregiver was assessed using
the Service Utilization and Resource Form ( Schneider et al.,
2001 ) dichotomized into one or more services versus no
services used. Caregivers reported on felt stress by rating
“ the degree, if any, that the participant ’ s present condition
interferes with your ability to carry on a normal life style, ”
coded from 1 ( no problem ) to 10 ( can no longer cope ).
Linear mixed models ( Fitzmaurice, Laird, & Ware, 2004 )
were computed on the trajectory of MMSE scores and CDR
scores from enrollment visit forward, with key independent
variables: RC and caregiver “ type ” (spouse or adult child of
the participant). The main effect of closeness (or caregiver
type) assessed whether scores on the dependent variable
were signifi cantly different, on average, between levels of
the main effect. The interaction with time tested whether or
not closeness (or caregiver type) was signifi cantly associ-
ated with decline over time on the MMSE or CDR. Mixed
model parameter estimates for all effects including time
give information about annual rates of change. Model fi tting
proceeded with initial models to test the effect of closeness
alone, then caregiver type alone. To determine whether ob-
served effects of closeness and caregiver type were con-
founded by AD severity, a fi nal model controlled for
indicators of dementia severity at enrollment visit (dementia
duration, functional status, and behavioral disturbances).
The quadratic effect of time (time 2 ) was examined to test for
curvilinear effects on cognitive and functional status trajec-
tories and to examine whether predictor variables exerted
curvilinear effects on these outcomes via interaction of the
time**2 term with each predictor. Effects of age, gender,
and education of the CR were also examined (along with
their interactions with time). All analyses were performed
using SPSS version 15.0 (Chicago, IL).
Cognitive status, as measured by the MMSE, varied across
time from Visit 1 ( M = 19.4, SD = 7.2) to Visit 6 ( M = 11.5,
SD = 10.2), whereas functional status, based on the Sum-
CDR, varied across time from Visit 1 ( M = 7.7, SD = 5.3) to
Visit 6 ( M = 14.6, SD = 7.9). Individual RC statements de-
scribing the current relationship between caregiver and “ CR ”
ranged from 1 ( strongly disagree ) to 4 ( strongly agree ) and
included the following: CR always understands what I value
in life ( M = 2.88, SD = 0.92), My relationship with CR is
close ( M = 3.35, SD = 0.76), My relative always makes me
feel that whatever I do for him/her, it is not enough (reverse
coded; M = 3.42, SD = 0.77), CR makes me feel like a special
person ( M = 3.27, SD = 0.71), CR is often critical of me (re-
verse coded; M = 3.29, SD = 0.75), and CR and I can always
discuss things together ( M = 2.80, SD = 0.90). The composite
closeness score had a baseline mean of 18.0 ( SD = 4.2).
Cronbach ’ s alpha reliability for the scale was .88. Caregiver
stress responses had a mean of 3.64 ( SD = 1.74) for adult
child and a mean of 3.93 ( SD = 1.88) for spouse caregivers
( p = .321), whereas coresidency was more common for
spouse (92%) than for adult child (22%) caregivers.
We examined attrition effects by comparing persons with
AD who remained in the study through all six semi-annual
visits with those who dropped out (or died) at some point after
the initial visit. These two groups did not differ on enrollment
visit age ( p = .390), education ( p = .128), gender ( p = .234),
whether coresiding with caregiver ( p = .455), whether institu-
tionalized ( p = .260), or caregiver gender ( p = .109).
In the initial MMSE model, there was a signifi cant Close-
ness × Time interaction ( p = .009): Higher levels of close-
ness were associated with a signifi cantly slower rate of
decline in MMSE scores ( Table 1 ). In a separate model
comparing caregiver type, there was also a signifi cant Type
× Time interaction ( p = .003); those with spouse caregivers
experienced a slower rate of decline than those with adult
child caregivers. A quadratic effect for time was consis-
tently nonsignifi cant in all models ( p = .27 – .40) as was the
interaction of the quadratic time effect and each predictor
( p = .26 – .97); thus, these terms were removed.
In the fi nal model, longer dementia duration ( p = .035)
and poorer baseline functional status ( p < .001) were associ-
ated with lower cognitive status (but not rate of progres-
sion), whereas higher closeness ( p = .048) and spouse
caregiver type ( p = .014) were associated with slower
progression. In this model, an average 1-unit increase per
by guest on October 29, 2015
NORTON ET AL.
closeness item (i.e., a 6-unit increase across the closeness
composite score) was associated with 0.72 points per year
slower MMSE decline. Participants with spouse caregivers
showed an average 1.16 points per year slower MMSE
decline than those with adult child caregivers. At each level
of closeness, participants with spouse caregivers had higher
MMSE scores and slower decline than those with adult
child caregivers ( Figure 1 ). Furthermore, within each care-
giver type, increasing closeness was associated with higher
MMSE scores. In intermediate models (data not shown), the
effects of age ( p = .718), gender ( p = .091), and education
( p = .275) of the person with AD were nonsignifi cant, so
they were removed from the fi nal model.
Results with assessment of functional capacities were
similar. In the initial mixed model of CDR, there was a sig-
nifi cant Closeness × Time interaction ( p = .020); higher lev-
els of closeness were associated with a signifi cantly slower
functional decline ( Table 2 ). In a separate model, there was
a signifi cant Type × Time interaction ( p = .041), indicating
that participants with spouse caregivers experienced a
Table 1. Mixed Models of Repeated MMSE Scores as a Function of
Caregiving Relationship and Caregiver Type, Controlling Also for
Additional Explanatory Factors (including age, sex, and education)
closeness Model 2: type
Model 3: full
Closeness × Time
Type × Time
0.15 ( p = .287) − 0.06 ( p = .557)
− 1.34 ( p = .113)
− 5.18 ( p = .000)
0.12 ( p = .048)
1.16 ( p = .014)
− 0.39 ( p = .035)
− 1.04 ( p = .000)
0.06 ( p = .962)
− 3.40 ( p = .000) − 5.20 ( p = .000)
0.16 ( p = .009)
1.44 ( p = .003)
− 0.07 ( p = .093)
Notes : Parameters are estimates of the average difference in MMSE score,
adjusted for all terms in the model; Type : 1 = spouse caregiver, 2 = adult child
caregiver (adult child is reference category); Closeness : range from 6 to 24;
Time 2 not signifi cant ( p = .529), so was removed; Closeness × Type × Time not
signifi cant ( p = .625), so removed from Model 3 and later models; age ( p = .718),
gender ( p = .091), and education ( p = .275) not signifi cant (nor interactions with
time), so were removed; Dementia duration × Time ( p = .084), Functional status ×
Time ( p = .650), and Behavioral disturbance × Time ( p = .198) were not signifi -
cant, so were removed; a simple model (data not shown) with only the effect for
time yields a parameter estimate indicating a 2.52-point average annual decline,
consistent with other studies cited herein with a typical 3-point average annual
decline on the MMSE. MMSE = Mini-Mental State Exam
Figure 1. Model-based adjusted MMSE trajectory by caregiver type (spouse
vs adult child) and relationship closeness (grouped into tertiles); MMSE range:
0 – 30. MMSE = Mini-Mental State Exam.
Table 2. Mixed Models of Repeated Functional Status (CDR) Scores
as a Function of Caregiving Relationship and Caregiver Type,
Controlling Also for Additional Explanatory Factors (including age,
sex, and education)
closeness Model 2: type
Model 3: full
Closeness × Time
Type × Time
Type × Time
− 0.12 ( p = .278) − 0.01 ( p = .941)
1.27 ( p = .189)
1.24 ( p = .002)
0.08 ( p = .433)
3.82 ( p = .026)
− 0.28 ( p = .007)
− 1.10 ( p = .291)
2.80 ( p = .000)4.40 ( p = .000)
− 0.12 ( p = .020)
− 0.90 ( p = .041)
− 1.71 ( p = .058)
1.11 ( p = .000)
0.18 ( p = .000)
Notes : Type : 1 = spouse caregiver, 2 = adult child caregiver (adult child is
reference category); Closeness : range from 6 to 24; Time 2 not signifi cant ( p =
.057), so was removed; age ( p = .361) and education ( p = .844) were not sig-
nifi cant (nor interactions with time), so were removed; Dementia duration ×
Time ( p = .886) and Behavioral disturbance × Time ( p = .100) were not signifi -
cant, so were removed. CDR = Clinical Dementia Rating.
Figure 2. Model-based adjusted functional trajectory (CDR) by caregiver
type (spouse vs adult child) and relationship closeness (grouped into tertiles);
CDR range: 0 – 30. CDR = Clinical Dementia Rating.
by guest on October 29, 2015
CAREGIVER CLOSENESS AND AD SYMPTOM PROGRESSION
slower rate of decline than did those with adult child care-
givers (nonsignifi cant quadratic term). In the fi nal model,
longer dementia duration and greater behavioral disturbance
were signifi cantly associated with poorer functional status
(both p < .001) but not rate of progression. The signifi cant
Closeness × Type × Time interaction ( p = .007, graphically
depicted in Figure 2 ) revealed that for each 1-unit increase
per closeness item (i.e., a 6-unit increase across the close-
ness composite score), participants with spouse caregivers
showed 1.7 CDR points per year slower functional decline
than those with adult child caregivers.
Other Covariate Effects
Caregiver stress and use of support services did not differ
by caregiver type. However, participants with spouse care-
givers were more likely to be living at home and to coreside
with the caregiver than those whose caregiver was an adult
child. Therefore, we constructed other models that adjusted
for coresidence. On average, MMSE scores were higher
among those who coresided with their caregiver ( p = .032),
but coresidence was not associated with rate of MMSE de-
cline ( p = .491; results not shown). Adjustment for coresi-
dence had negligible change on the apparent effects of other
factors in the model.
This is the fi rst 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, partici-
pants declined more slowly in cognition and functional ca-
pacity, even after adjustment for several potential confounders.
These fi ndings were stronger when caregivers were the
spouses of the participants with AD. Furthermore, effects ob-
served in the present study were on the same order of magni-
tude 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 pla-
cebo was 1.37 MMSE points annual change (95% CI = 1.13 –
1.61) measured over an interval ranging from 6 to 12 months.
Our fi ndings 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 par-
ticular 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 in-
vestment model support the notion that such commitment
makes spouses more willing to accept a caregiving role and
sacrifi ce 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 , 1993) and Graham and Bassett (2006) affi rm the dy-
namic 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 suc-
cess of this intervention was a sense that persons with demen-
tia felt listened to and understood by their caregivers.
One way in which closer relationships might predict im-
proved outcomes is their tendency toward more successful
and adaptive care management strategies. For example, en-
gagement 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, how-
ever, that caregivers in our sample who reported higher lev-
els 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
by guest on October 29, 2015
NORTON ET AL.
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 in-
strument was originally designed for studying adjustment to
nursing home placement ( Whitlatch et al., 2001 ). Notwith-
standing its apparent face validity, this scale has not specifi -
cally been validated for measurement of such important
variables as communication quality, mutual respect, empa-
thy, and affection. Furthermore, given the nature of the sam-
ple, we cannot assess the extent to which the participants ’
perceptions of RC might be predictive of clinical course.
Seventy-fi ve 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 suffi cient
numbers to be able to stratify analyses by all combinations
of spouse versus adult child caregiver type, gender of care-
giver, and gender of CR. Thus, the study of differential ef-
fects of these eight combinations awaits further data
collection, with results presented here somewhat more gen-
eralizable to dyads with female caregivers. Finally, our fi nd-
ings may be relatively specifi c 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 im-
portant 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, particu-
larly 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, fi ndings were robust after control for
dementia severity, raising questions about caregiver strate-
gies that may promote better functioning in dementia. Fur-
thermore, 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 refl ect caregiver strategies
that fl exibly adapt to the needs of the person with AD, en-
couraging, when appropriate, participation in cognitively
and socially stimulating activities, which help promote sus-
tained 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, in-
terdependence 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.
National Institutes of Health grants AG021136 , AG011380 , AG031272 ,
AG018712 , and AG027841 including study design, data collection, data
management and analysis, interpretation of the data and preparation, re-
view, and approval of the manuscript.
The authors wish to thank the study participants and their families for
their generosity and willingness to participate. Other Cache County Study
investigators involved in the project include (in alphabetic order): James
Anthony, PhD; Erin Bigler, PhD; Ron Brookmeyer, PhD; James Burke,
MD; Michelle Carlson, PhD; Eric Christopher, MD; Jane Gagliardi, MD;
Andrea Hart, PhD; Kate Hayden, PhD; Christine Hulette, MD; Liz Klein,
MPH; Carol Leslie, MA; Richard A. Miech, PhD; John Morris, MD;
Ronald Munger, PhD; Chiadi Onyike, MD; Ron Petersen, MD; Roxane
Pfi ster, MS; Carl Pieper, PhD; Brenda Plassman, PhD; Pritham Raj, MD;
Russell Ray, MS; Linda Sanders, MPH; Ingmar Skoog, MD; David C.
Steffens, MD; Martin Steinberg, MD; Marty Toohill, PhD; Leslie Toone,
MS; Jeannette J. Townsend, MD; Heidi Wengreen, PhD; Nancy West,
PhD; Michael Williams, MD; Bonita W. Wyse, PhD; and Peter P. Zandi,
PhD. Portions of this paper were presented at the annual conference of the
American Association for Geriatric Psychiatry, Orlando, Florida, in March,
Address correspondence to Maria C. Norton, PhD, Department of
Family, Consumer and Human Development, Utah State University, 2905
Old Main Hill, Logan, UT 84322-2905. Email: email@example.com
* These authors share equal role as senior author.
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Received October 27 , 2008
Accepted May 25 , 2009
Decision Editor: Rosemary Blieszner, PhD
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