Advances in Physical Education
2012. Vol.2, No.2, 68-72
Published Online May 2012 in SciRes (
Copyright © 2012 SciRes.
Does Adherence Moderate the Effect of Physical or Mental
Training on Episodic Memory in Older Women?
Andrea Evers1, Verena Klusmann1, Ralf Schwarzer2,3, Isabella Heuser1
1Department of Psychiatry, Charité Universitätsmedizin Berlin, Berlin, Germany
2Department of Psychology, Freie Universität Berlin, Berlin, Germany
3Warsaw School of Social Sciences and Humanities, Wroclaw, Poland
Received February 24th, 2012; revised March 27th, 2012; accepted April 8th, 2012
Objective: The aim was to investigate the overall amount of time spent on physical or mental activity
training units (i.e., adherence) as a predictor of episodic memory performance in older healthy women.
Methods: Women (N = 171, aged 70 - 93 years) took part in a 6-month randomized controlled trial
(physical activity or computer training, 3 times weekly). Pre- and post-intervention episodic memory and
adherence were assessed. Adherence covers the objectively measured frequency of training participation
including travel time to and from course sites. Results: Within the physical exercise group, adherence (β
= .19, p = .03) had positive effects on cognitive performance. In the computer group, an interaction be-
tween adherence and pre-intervention episodic memory (β = .17, p = .056) indicated improvement for
low-ability women. Conclusions: Adhering to a stimulating mental or physical activity intervention is a
prerequisite for healthy older women to maintain or slightly improve their episodic memory performance.
Travel activity should be taken into account to cover an overall stimulation. Adherence to mental activity
training indicates a moderating effect of mental activity training on episodic memory. Predominantly
low-ability women improve their episodic memory performance. In contrast, adherence to physical activ-
ity training is positively associated with cognitive performance, regardless of pre-intervention episodic
memory performance.
Keywords: Episodic Memory; Intervention; Adherence; Older Women; Exercise
A decline in cognitive performance, especially with regard to
episodic and working memory, is commonly observed with in-
creasing age (Baltes, Staudinger, & Lindenberger, 1999; Singer,
Verhaeghen, Ghisletta, Lindenberger, & Baltes, 2003). Obser-
vational studies suggest that physically or mentally demanding
activities counteract this decline (Hogan, 2005; Mackinnon,
Christensen, Hofer, Korten, & Jorm, 2003), and experimentally
controlled intervention studies find a positive effect of these
activities on mental status in older people (Colcombe & Kramer,
2003; Heyn, Abreu, & Ottenbacher, 2004).
Adherence to trainings is classically defined as the frequency
of participation in a specific activity (Newson & Kemps, 2006)
or the extent to which a person’s behavior corresponds to a
recommendation, emphasizing the active role of the participant
(Shields, Brawley, & Lindover, 2005). Adherence effects have
to be studied for the following reasons: First, direct effects of
adherence on outcomes often remain unclear, although inade-
quate adherence is presumed to reduce the effectiveness of
interventions (Brawley & Culos-Reed, 2000). Second, training
responses among older adults vary. Individuals with lower
baseline memory ability or at risk for impaired executive func-
tion showed the greatest improvements in memory trainings,
for example (Langbaum, Rebok, Bandeen-Roche, & Carlson,
2009). Third, measurement and assessment tools for adherence
across various health behaviors do also diverge and there is no
gold standard (Vitolins, Rand, Rapp, Ribisl, & Sevick, 2000). A
strong relation between adherence and outcomes was found for
continuous but not for dichotomous measures (DiMatteo, Giordani,
Lepper, & Croghan, 2002). An adequate definition of adher-
ence according to the studied behavior is mandatory to allow
for unambiguous conclusions regarding the dose-response rela-
tionship and of treatment consequences. According to Newson and
Kemps (2006) the measure of adherence to activities should
capture the overall level of stimulation.
Aims of the Study
In a recently reported randomized controlled trial (Klusmann
et al., 2010) healthy women aged 70 years and older were allo-
cated to either a 6-month standardized physical activity (i.e.,
exercise course), mental activity (i.e., a computer course), or a
control group. Participants in both intervention groups similarly
showed better cognitive performance change over 6 months
than the controls. Here, we report on adherence to these com-
puter and exercise courses and effects of adherence on episodic
memory performance. We hypothesized that those women with
lower baseline memory benefit most from adherence, regardless
of the intervention group. We conceptualized adherence as
“course attendance including travel time to and from the course
sites” (Evers, Klusmann, Schwarzer, & Heuser, 2011b: p. 448).
Intervention and Participants
We present adherence and its effect on cognitive performance
from a recently reported randomized controlled trial (Klusmann
et al., 2010), consisting of 259 healthy community-dwelling
women aged 70 years and older. All participants were both
unfamiliar with the computer and exercised less than one hour
per week. One hundred and seventy-one women (age M = 73.6
years, SD = 4.2) were randomized to two behavioral intervene-
tion programs: one physical training (n = 86), comprising aerobic,
stretching, balance and muscle workouts, and one computer
training (n = 85), comprising learning how to use common
software and hardware. Both intervention programs consisted
of standardized group trainings (7 groups à 12 participants),
with the intensity of 90 minutes, the frequency of three times
weekly and the duration of 6 months. On average, 73 course
units were offered to each group (range 70 - 74). Group train-
ings were conducted successively by a certified exercise or
qualified computer trainer in different locations throughout
Berlin which all were accessible by public transportation. It
comes with the design of our study that adherence data exist
solely for the intervention groups. The control group was in-
structed to live their habitual life. This article focuses on the
association between adherence and episodic memory perform-
ance. Motivational and volitional aspects of adherence are dis-
cussed elsewhere (Evers, Klusmann, Schwarzer, & Heuser, 2011a).
Baseline assessments and outcome measurements. Baseline
assessments, study outcome measures, general cognitive status
and demographic data were collected in a face-to-face situation.
There were no missing data. Study outcome measures were
assessed after termination of the 6-month intervention (Klus-
mann et al., 2010). The following analyses focus on test scores
of the Free and Cued Selective Reminding Test (FCSRT; Busch-
ke, 1984), a valid episodic memory test to maximize learning
while controlling attention and cognitive processing. The task
requires learning and recall of 16 words presented as pictures
using semantic categories as cues for encoding. The dependent
variable is the sum score of three recall trials in a short delay
condition, that is, separated by brief distractors (range of scores
= 0 to 48).
Adherence. The number of each 90-minute course unit at-
tended (CA) was recorded by all trainers for each participant
and intervention unit. The average individual travel time to and
from course sites (TT; minutes), which was reported by the
participants at follow-up, was added to each attended course
unit. Adherence (A) was calculated by multiplying the number
of course units attended (CA) with the duration of one interven-
tion unit (i.e., 90 minutes) plus travel time to and from course
locations (TT):
ACA90 minutesTT (1)
The result was converted into units of hours for reasons of
Statistical Analyses
Hierarchical regression analyses were conducted separately
for both experimental groups. FCSRT follow-up scores were
regressed on FCSRT baseline measurements and adherence
(second step), controlling for age and educational level (first
step). Third, interaction terms of baseline measurements and
adherence were added for moderator testing. Variables were
standardized to attain a common metric and prior to moderator
testing. We used an SPSS macro provided by Hayes and Mat-
thes (2009) to examine the interaction at three levels (mean ± 1
SD) of adherence. An additional output provided by the macro
assists in the plotting of the conditional effect of adherence. All
statistical analyses were performed using SPSS 19.0.
For regression analyses, data of all participants with fol-
low-up assessment on the FCSRT were used regardless whether
they discontinued the intervention at any point in time (inten-
tion-to-treat). Age and educational level were included as cova-
riates. Of 171 women who started the interventions, 161 women
participated in the 6-month follow-up assessment, i.e., 80 women
in the exercise condition and 81 women in the computer condi-
tion. Data of the sample characteristics are summarized in Ta-
ble 1. Experimental groups did not differ regarding demo-
graphics and general cognitive status at baseline, and no sig-
nificant group difference at baseline and follow-up in test
scores of FCSRT was found; both intervention groups showed
stable levels of performance.
Adherence. Adherence was significantly lower in the exer-
cise group compared to the computer group, t(159) = 3.24, p
= .001. However, average travel time did not differ between
these two groups, t(159) = 1.01, p = .316. Adherence did not
significantly correlate with any of the baseline variables in none
of the intervention groups.
Regression Analyses
Effects of adherence on post-test episodic memory perform-
ance are presented separately for both intervention groups.
Physical exercise group. The results of hierarchical regression
analyses revealed a non-significant influence of the covariates
age and educational level on FCSRT post-test scores. In the
second step, baseline scores of the FCSRT were significant
Table 1.
Characteristics of the study population and descriptive statistics.
Exercise group
(n = 80)
Computer group
(n = 81)
Age (yr) 73.5 ± 4.0 73.5 ± 4.2
Marital status
Widowed (n) 26 (33%) 29 (36%)
Married (n) 23 (29%) 13 (16%)
Divorced (n) 22 (28%) 24 (30%)
Other (n) 8 (10%) 9 (11%)
Years of education 11.8 ± 2.5 12.1 ± 2.6
Mini-Mental State Examination28.8 ± .9 28.8 ± .9
Free word recall FCSRT short
delay, pre-score 35.7 ± 3.9 35.1 ± 4.6
Free word recall FCSRT short
delay, post-score 36.1 ± 4.3 34.7 ± 5.2
Travel time to courses,
single way (min) 43.1 ± 16.3 40.4 ± 17.2
Course attendance (h) 75.7 ± 28.5 92.9 ± 20.6
Adherence (h) 146.5 ± 62.5 176.9 ± 53.3
Note: Unless otherwise noted, means ± SDs are reported. The range of scores on
the Mini-Mental State Examination (Folstein & McHugh, 1975) is 0 to 30, with
scores above 26 indicating no cognitive impairment. The range of scores on the
free recall FCSRT short delay is 0 to 48 (sum score of three recall trials short
delay separated by distracters). Adherence is defined as the number of course
units attended including travel time, converted into units of hours.
Copyright © 2012 SciRes. 69
predictors of FCSRT post-test scores (β = .64, p < .001). Adhe-
rence emerged as a significant predictor (β = .19, p = .031, R2 =
43%). The inclusion of the interaction term of adherence and
baseline scores of the FCSRT in the third step did not increase
the variance explained.
Computer group. The results of hierarchical regression analyses
revealed a significant influence of age (β = .35, p = .002) and
a non-significant influence of educational level on FCSRT
post-test scores. In the second step, baseline scores of the
FCSRT emerged as significant predictors of FCSRT post-test
scores (β = .58, p < .001). Adherence approached significance
(β = .15, p = .089, R2 = 44%). In the third step, the inclusion of
the interaction term of adherence and baseline scores of the
FCSRT (β = .17, p = .056) increased the variance explained
(R2 = 46%), but the influence of adherence did not reach sig-
nificance (β = .12, p = .178).
Plotting the interaction at three selected levels of adherence
(mean ± 1 SD) indicated that women with low test scores of
FCSRT short delay at baseline and high adherence were pre-
dicted to outperform people with the same low baseline scores
but low adherence (Figure 1). Simple slope analyses revealed
that the conditional effect of adherence was significant (p
= .014) for women who performed 1 SD below group mean
(<30.5) at pre-testing. In other words, spending about 3 hours
three times a week for six months (i.e., 230 hours/73 units)
yielded an optimal benefit for this group. Table 2 contains the
findings of the regression analyses.1
The objective of the present article was to investigate the in-
fluence between adherence in two different intervention pro-
grams and episodic memory performance. In our study, adherence
represented the overall amount of time spent on course partici-
It has been reported that the relationship between adherence
and outcome measures is complex and that variability in re-
sponsiveness to training is considerable (DiMatteo et al., 2002).
Although the intervention groups differed significantly in adhe-
rence, no significant difference in pre- and post-test scores of
episodic memory emerged. On average participants maintained
their level of performance and we found baseline memory per-
formance to have a strong influence on the outcome of memory
In the exercise group, adherence emerged as a weak predictor
of episodic memory performance. A moderating effect of adhe-
rence on the association between baseline and post-test scores
was not found. Thus, we conclude that effects on episodic
memory seem to be due to 90 minutes of combined exercise
training as proposed in Colcombe and Kramer (Colcombe &
Kramer, 2003).
For the mental activity group, adherence did not predict epi-
sodic memory performance; however, a moderating effect of
adherence indicated beneficial effects of adherence for low-
baseline women only. We reason that the negative influence of
age might be mitigated if older women spent time in a chal-
lenging mental activity.
Travel time seems to boost intervention effects by an addi-
tional physical and mental stimulation. All but three partici-
pants were public transit commuters or walked to course loca-
tions. Spending about 80 minutes on average for travelling
(round trip) on each 90-minute course unit appears to have
contributed to an additional, albeit unspecific, activity (Wener
& Evans, 2007). We found the computer course to have im-
proved slightly in the 6-minute walking test (Klusmann et al.,
2010). Hence, one could carefully assume that the positive
effect of adherence (including travel activity) on cognitive per-
formance is due to an increased fitness level by an additional
“transportation activity” (Hamer & Chida, 2008).
Participants in the computer course similarly might have
been mentally stimulated while being “en-route”. They likely
have been reflecting upon or occupying themselves with their
course work, reworking previous course units and preparing
themselves for current units. Thereby the cognitively stimulat-
ing effect might have been continued beyond the actual inter-
vention. These mental activities seem to be less relevant in a
physical activity course which relies much less on teaching
contents of previous lessons. To conclude, travel time may be
an additional physical and/or mental stimulation, depending on
the content of courses attended.
By amending adherence with the information of the time
needed to participate, an overall level of stimulation is covered
(Newson & Kemps, 2006). Furthermore, the frequency of par-
ticipation is often based on self-reported data (e.g., Glazebrook
& Brawley, 2011); the strength of our approach is that the num-
ber of course units attended was measured objectively.
Limitations of the Study
The reported adherence effects were derived by relying on
the outcome of one episodic memory test. Furthermore, a dose-
response effect of activity on cognition could not be calculated,
because participants were not randomized to different groups of
intensity, and adherence in our study turned out to be consistently
high. In future studies, pedometers could be used to measure
additional physical activity (Wener & Evans, 2007). Participants in
1Repeating the analyses with adherence excluding travel activity, adherence
emerged as a significant predictor for the activity group only (activity group:
β = .17, p = .045; computer group: β = .05, p = .568). The inclusion of the
interaction term of adherence and baseline scores of the FCSRT in the third
step approached significance (activity group: β = .16, p = .080; computer
group: β = .16, p = .090). The positive interaction in the activity group
indicated improvement for high-ability women only, i.e., women who per-
formed 1 SD above group mean at pre-measurements of the FCSRT.
Figure 1.
Computer group (n = 81): Prediction of post-test scores on FCSRT
short delay at three different values of adherence (mean ± 1 SD).
Spending a lot of time (i.e., on average 230 h in 6 months) has a posi-
tive effect for participants performing 1.5 SD below mean at baseline
memory performance.
Copyright © 2012 SciRes.
Copyright © 2012 SciRes. 71
Table 2.
Regression coefficients for variables predicting post-test episodic memory performance (FCSRT short delay) for both intervention groups.
Exercise group Computer group
Variable β SEB p R2 2
R β SEB p R2 2
Step 1
Age .15 .11 .179 .35 .11 .002
Years of education .16 .11 .158 .03 .04 .11 .692 .10
Step 2
Age .04 .09 .627 .21 .09 .017
Years of education .03 .09 .705 .03 .09 .771
Baseline .64 .09 .000 .58 .09 .000
Adherence .19 .09 .031 .40 .43 .15 .09 .089 .35 .44
Step 3
Age .04 .09 .691 .20 .09 .023
Years of education .04 .09 .652 .05 .09 .552
Baseline .66 .09 .000 .55 .09 .000
Adherence .16 .09 .075 .12 .09 .178
Baseline x Adherence .11 .10 .210 .01 .43 .17 .07 .056 .03 .46
Note. Baseline refers to pre-test score of free word recall FCSRT short delay; covariates: age, years of education.
our study were healthy and well-educated, resembling a sample
of successfully aging women, and ceiling effects are likely to
have played a role.
Adhering to a challenging physical or mental training inter-
vention enables healthy older women to maintain or slightly
improve their episodic memory performance. Adherence effects
depend on participants’ pre-intervention cognitive status: Ad-
hering to a physical activity intervention is beneficial for high-
and low-ability women; predominantly low-ability women
improve their episodic memory by spending a large amount of
time on a stimulating mental activity intervention. In doing so,
adherence covers not only the frequency of participation but
also travel activity as an additional physical and mental stimu-
This research was funded by non-profit sponsors: German
Research Foundation: Deutsche Forschungsgemeinschaft (DFG),
Doctoral Program “Neuropsychiatry and Neuropsychology of
Aging” (grant 429); Gertrud and Hugo Adler Foundation. The
study was developed and designed under the leadership of Pro-
fessor Isabella Heuser who was the recipient of the grants.
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