Section of Ageing and Health, Department of Medicine, University of Dundee, Ninewells Hospital and Medical School, Dundee
Department of Psychiatry, University of Dundee, Ninewells Hospital and Medical School, Dundee
Section of Ageing and Health, Department of Medicine, University of Dundee, Ninewells Hospital and Medical School, Dundee
Correspondence: Professor Marion E. T. McMurdo, Section of Ageing and Health, Department of Medicine, Ninewells Hospital and Medical School, Dundee DDI 9SY, UK. Tel: 01382 632436; fax: 01382 660675; e-mail m.e.t.mcmurdo{at}dundee.ac.uk
Declaration of interest M.E.T.M. is co-director of DD Developments, a University of Dundee company providing exercise classes for older people and whose profits support research into ageing.
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ABSTRACT |
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Aims To determine whether exercise is effective as an adjunct to antidepressant therapy in reducing depressive symptoms in older people.
Method Patients were randomised to attend either exercise classes or health education talks for 10 weeks. Assessments were made blind at baseline, and at 10 and 34 weeks. The primary outcome was seen with the 17-item Hamilton Rating Scale for Depression (HRSD). Secondary outcomes were seen with the Geriatric Depression Scale, Clinical Global Impression and Patient Global Impression.
Results At 10 weeks a significantly higher proportion of the exercise group (55% v. 33%) experienced a greater than 30% decline in depression according to HRSD (OR=2.51, P=0.05, 95% CI 1.00-6.38).
Conclusions Because exercise was associated with a modest improvement in depressive symptoms at 10 weeks, older people with poorly responsive depressive disorder should be encouraged to attend group exercise activities.
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INTRODUCTION |
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METHOD |
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The study was a randomised controlled trial approved by the Tayside Committee on Medical Research Ethics. All patients (n=86) gave written informed consent prior to inclusion and subsequently were allocated randomly to one of two groups: a treatment group (exercise) or a non-exercise social control (health education talks). Allocation to treatment was made by the research nurse (A.S.M.), separate from the assessors, by opening sealed envelopes supplied in sequence by an individual not directly involved in the study (M.E.T.M.) and prepared from a computer-generated random number table. All patients continued to take antidepressant therapy throughout the trial.
Interventions
Exercise
The exercise class used is open to the public and run by the University of
Dundee for people aged 60 years and over. This particular class was chosen
because it has been shown already to be both acceptable to older people and
effective (McMurdo et al,
1997). Each of the exercise classes lasted for 45 min and
comprised predominantly weight-bearing exercise performed to music, led by an
instructress from a podium in the centre of the hall. There was a warm-up
period of 5-10 min at the start and a cool-down period at the end of each
session. The format of the class contained elements of endurance, muscle
strengthening and stretching. The class was followed by optional refreshments.
Participants were asked to attend classes twice per week for 10 weeks and the
attendance at the class was recorded.
Health education (non-exercise control)
Those randomised to the control group of the study were asked to attend
twice-weekly health education talks for a period of 10 weeks at Ninewells
Hospital and Medical School, Dundee. Talks lasted for 30-40 min and were
delivered by medical and nursing staff and staff from the professions allied
to medicine. Topics were depression, anxiety, relaxation, memory problems,
safe alcohol use, healthy ageing, exercise, healthy hearts, diet, bone and
dental health, sleep, accidents at home, structuring time and homoeopathic
medicine. Talks were followed by a 15-min question-and-answer session and
optional refreshments were available. The attendance was recorded. The series
of talks also was open to the general public, in order to produce a mixed
population similar to the exercise class.
Assessment and outcome measures
Patients were assessed on three occasions: baseline, 10 weeks and 34 weeks.
The interventions began 1 week after baseline measurements had been recorded.
The assessments were made at clinical interview by one of two psychiatrists
who were blind to treatment allocation and remained blind for the duration of
the study. The primary outcome was seen with the 17-item Hamilton Rating Scale
for Depression (HRSD; Hamilton,
1960). This instrument was chosen because it has been shown to be
useful in the assessment of community-dwelling older people
(Onega & Abraham, 1997;
Mottram et al, 2000),
although it was not originally designed for use with this group. Its use also
permits comparison of our findings with those from the international
depression literature. Secondary outcomes were seen with the GDS, Clinical
Global Impression (CGI; Guy,
1976) and Patient Global Impression (PGI;
Guy, 1976). A second depression
score (GDS) was included both as a screening instrument (for which it was
developed) for study eligibility and as a secondary outcome measure, because
it is the only such instrument devised specifically for use with an older
population. However, use of such a self-report measure as the primary outcome
of this study would have rendered the results highly susceptible to patient
expectation bias.
Statistical analysis
The primary outcome variable was change in the HRSD from baseline. For the
purposes of this study, response was defined as a 30% or greater
decrease from the baseline score. To address the possibility of dependencies
between the measured variables and serial correlation within subjects on
consecutive occasions, changes from baseline in all four variables were
assessed using the appropriate analysis for repeated measures
(Crowder & Hand, 1990).
Fisher's exact test and exact contingency tests were used for comparison of
numbers of patients who responded to treatment. All analysis was by
intention-to-treat.
It was estimated that in order to detect a 30% difference between the percentage of responders in the control group compared with that in the exercise group at the P=0.05 level of significance, a sample size of 40 subjects per group would be required to give a power of 90%. Data on poorly responsive depression are scant but the proportion of responders in the control group was reasonably anticipated to be 10%, compared with an anticipated 40% in the exercise group.
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RESULTS |
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Response to intervention
Primary outcome measure (HRSD)
The primary outcome of interest was the proportion of participants
achieving a response, defined as a 30% reduction in HRSD
score from baseline. At 10 weeks 23/42 (55%) of the exercise group achieved a
response, whereas in the control group only 14/43 (33%) had achieved the
30% reduction (OR=2.51, P=0.05, 95% CI 1.00-6.38). Further
analysis using the Mann-Whitney test revealed no discernible difference
between the two groups in overall effect on the HRSD score (U=1683,
P=0.28, 95% CI difference in medians -0.20 to 0.06).
Other outcome measures
Secondary outcome measures were seen with the GDS, CGI and PGI. At the end
of the 10-week intervention period both the exercise and the control group had
scores that were statistically significantly different from baseline, with no
difference between the two groups (Table
2). This observation persisted at 34 weeks in both the exercise
and the control groups.
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DISCUSSION |
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Both groups showed statistically significant differences from baseline in all outcome measures at both 10 and 34 weeks, with no between-group difference. This is likely to have been the result of regression to the mean, participation in the trial or due to other external factors.
Comparisons with previous studies
The existing literature on exercise and depression focuses mainly on
younger adults and is almost uniformly positive, suggesting that a large
proportion of patients with depression can be encouraged to exercise
(Martinsen et al,
1985,
1989). Attendance at the
exercise group in our study was significantly less than the 90% reported in
all three previous studies in this age group
(McNeil et al, 1991;
Singh et al, 1997;
Blumenthal et al,
1999). A 59% mean attendance rate was achieved in our study over a
10-week period in the exercise group. A trial by the authors with older
subjects without depression using the same exercise class intervention
achieved a mean attendance of 83% over a 32-week period
(McMurdo et al,
1997).
The exercise intervention used for this study was already established, having catered for the exercise needs of older people for over 20 years. This is in contrast to other studies in both younger and older adults where the exercise intervention had been devised for the purposes of the study, often being carried out in a small group or on an individual basis. If exercise is to become a possible treatment option for older patients with depression, it must be both acceptable and accessible to old people. Our study suggests that this may be more difficult to achieve than previously reported. Contrary to all other research in both younger and older adults, our experience shows that depressive symptoms can act as a barrier to participation in an exercise class.
Methodological considerations
The biggest challenge of this study was recruitment. A total of 1885
patients were considered for entry to the study and yet fewer than 5% were
randomised. Scrutiny of the literature reveals a dearth of research in older
adults with depression, and the extreme difficulty of recruitment is described
by the few researchers who have attempted clinical trials with this group
(Schlernitzauer et al,
1998; Stevens et al,
1999). Yastrubetskaya et al
(1997) reported exceptional
difficulties encountered when recruiting elderly patients for a study to test
a new antidepressant: mirroring our own experience, fewer than 5% of patients
screened for study entry were eventually recruited. Schlernitzauer et
al reported their 5-year experience of recruiting patients for a study of
depression associated with bereavement. During this period only 65 patients
were recruited, which is an average of one patient per month. The authors
reported that by far their most successful method of recruitment was from
response to a media campaign, which generated 54% of the total study group.
The inclusion of patients who responded to an advertisement in our own study
may limit the generalisability of our results but research in late-life
depression trials suggests that the response in such solicited patients does
not differ from those recruited by consultation referral
(Miller et al, 1997).
Our efforts confirm, however, that although recruitment was laborious and
difficult, it was achievable in this patient group.
The inclusion of a structured social control group in our study is of particular methodological importance. This is crucial in attempting to disentangle the diversional and psychosocial effects of coming together as a group from the effects of exercise itself. The therapeutic effects of a structured social intervention should not be underestimated in a group for which loneliness and isolation may be common. It is therefore important that future studies of depression in older people include an appropriate control.
It is possible that the preponderance of women in the exercise group may have introduced a bias to our results. The prevalence rate of depression among older women appears to decline with advancing years (Henderson et al, 1998) but female gender continues to be cited as a significant risk factor for developing late-life depression (Green et al, 1992). We are, however, aware of no literature to suggest that gender influences response to treatment in late-life depression. Analysis of our results showed no difference between the responses of men and women in either group.
A follow-up assessment period of 24 weeks was chosen for this study, to redress the short follow-up periods used in other studies. Although the 24-week follow-up is substantially lengthier than used in previous studies, a recent meta-analysis of all studies examining the effects of exercise on depression suggests that this follow-up period should be longer still (Lawlor et al, 2001). A 1-year follow-up for our study is planned.
The implications of our findings for the health service are that time-limited, brief, structured group exercise sessions can be associated with a modest improvement in depressive symptoms in a group of patients for whom response to pharmacological treatment may be limited. The many physical health benefits associated with exercise in old age are well known. Our findings suggest that older people with poorly responsive depressive disorder should be encouraged to attend group exercise activities.
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Clinical Implications and Limitations |
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LIMITATIONS
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ACKNOWLEDGMENTS |
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The authors are grateful to Miss Dorothy Dobson of the University of Dundee's over-60s' exercise class, Miss Ruth Miller from the Department of Epidemiology and Public Health for assistance with data entry, Dr Fergus Daly from the Department of Medicine for help with statistical analysis, Miss Adele Makarewicz for practical and secretarial support, colleagues who gave the health education talks and, of course, all the patients who participated in the trial.
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Received for publication August 1, 2001. Revision received January 9, 2002. Accepted for publication January 14, 2002.
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