2Aug
Introduction
One might be excused for thinking that exercise is a cure for everything, based on the spate of publications demonstrating its benefits. There is a new study that has examined the use of aerobic exercise in treating older patients with major depression. Depression in the elderly is relatively common – its prevalence has been quoted as ranging from 5% to 10% in elderly community dwellers, with levels reaching 18% in nursing home residents. There is an increase mortality risk – not related to suicide – that it is not in considerable.
Antidepressant drugs are successful in the treatment of depression in at least two-thirds of patients, but they carrying unwanted side effects which many reduce compliance – e.g. nausea, anorexia, diarrhea, insomnia, sedation, nervousness, dizziness, tremor, and decreased sexual function. The study summarized here compares the use of aerobic exercise as an alternative or complementary treatment for depression with antidepressant medication in older patients.
Method
Participants were recruited to the study, which was conducted at three centers in the USA, through advertisements and letters to local physicians and mental health facilities. At an initial screening interview, relevant parts of the Diagnostic Interview Schedule and the 17-item Hamilton rating scale for depression (HAM-D) were administered. Participants were considered eligible if they met the DSM-IV criteria for major depressive disorder (MDD) and if they had a severity score of at least 13 on the HAM-D.
Potential participants were excluded if they were taking antidepressants or other medications that would interfere with random assignment to receive the drug or exercise treatment. They were also excluded if there were contraindications to aerobic exercise (e.g. orthopedic problems or cardiopulmonary disease).
In addition to the HAM-D, the Beck Depression Inventory (BDI) was used as a self-report on symptoms relating to self-dislike, suicidal thoughts, insomnia and sadness. Four additional sets of self-report tests were administered before and at the end of the 16-week intervention.
At baseline and at the end of the four-month intervention participants underwent an aerobic treadmill test with continuous ECG monitoring, and an increasing workload. Analysis of expired air and time to exhaustion (or other standard clinical endpoint) was used to estimate aerobic capacity.
The intervention (randomly assigned) was exercise, medication, or a combination of both. Stratified randomization was used to ensure equal distribution of mild vs. moderate-to-severe depression patients to each treatment group. The exercise sessions, which were supervised, were done three days a week for 16 consecutive weeks. The individual training range used was 70% to 85% of the heart rate reserve as calculated from the maximum heart rate achieved during the first treadmill test. A 10-minute warm-up period was followed by 30 minutes of continuous walking or jogging within the training range, followed by a 5-minute cool-down period.
The medication used was sertraline, a selective serotonin re-uptake inhibitor, initiated at a dose of 50 mg and titrated until a well-tolerated therapeutic dose was achieved, with 200 mg the upper limit.
Results
A total of 156 patients were randomized into the study. Their mean age was 57 years (range 50 to 77). The 3 treatment groups did not differ regarding age, sex, level of education, marital status, income, ethnic background, or history of recurrent depression. Their mean HAM-D and BDI scores were not statistically different from each other.
There were 32 dropouts before the end of the 16-week intervention. The dropout rates were the same across treatment conditions in the two groups receiving medication (5 dropout in each case because of adverse effects), and in the two exercise groups (4 and 3 dropped out because of dissatisfaction with exercise regimens). Compliance with the various regimens was satisfactory – patients on medication took 95% or more of their prescribed dosage, and attendance for exercise was 90% in one group and 92% in another. The mean time in target heart rate range was 82.4% in both exercise groups.
Not unexpectedly, patients in the exercise and combination groups had significant improvement in their aerobic capacity by the end of the intervention, while patients in the medication-only group did not.
All three treatment groups showed a significant reduction in depressive symptoms over the 16 weeks, as measured by the HAM-D and BDI scores. There were no significant differences in treatment effects with regard to the improvements in HAM-D or BDI scores. Based on the DSM-IV criteria for MDD, there were no significant differences across treatment groups in the proportions of patients classified as clinically depressed – 60.4% in the exercise-only group, 68.8% in medication-only group and 65.5% in the combination group.
The rate of treatment response was faster in the medication-only group patients – they showed a more rapid initial therapeutic response within the first few weeks, compared with patients in the other groups. Moreover, mildly depressed patients responded more quickly to the combination of medication and exercise than did moderately-to-severely depressed patients. These effects were seen in both the HAM-D and the BDI scores.
Comment
This study shows that a program of aerobic exercise is a feasible treatment modality for elderly patients with major depressive disorder. Dropout rates were comparable with those for the other treatment regimens, and a clinical benefit was shown in the slight but relevant improvements in aerobic capacity associated with exercise. The results of the study are comparable in magnitude with those for studies using sertraline in other clinical trials, as well as with the extent of improvements reported after psychosocial intervention.
The authors speculate on possible mechanisms responsible for the reduction in depressive symptoms with aerobic exercise. The improved aerobic capacity may have accounted for part of the effect. Other mechanisms, including alterations in central norepinephrine activity, increased secretion of beta-endorphins and reduced activity of the hypothalamopituitary axis, are mentioned as ways in which exercise might improve mood. Psychological effects – improved self-efficacy or self-esteem, lessened negative thought patterns, greater social interactivity – might also be responsible.
Before too much importance is attached to these findings, it should be noted that the study was relatively short-term (16-weeks), and therefore gives no indication about relapse or long-term recurrence rates, which can occur in 50 to 80% of patients in drug treatment studies. Moreover, for obvious reasons the study could not include a “no treatment” group, so that the placebo effect in this patient population was not assessed; a placebo response is commonly as high as 30% in antidepressant drug studies. Nevertheless, depression can reasonably be added to the growing list of conditions where “exercise is good for you”.
