Results from this study indicate that a sixteen week program of moderate intensity aerobic physical activity plus sleep hygiene education is effective in improving self reported sleep quality, mood and quality of life in older adults with chronic insomnia. These results highlight the potential of structured physical activity programs to improve the effectiveness of standard behavioral approaches for the treatment of insomnia, particularly in a sedentary older adult population.
The effect size for the improvements in sleep duration and subjective sleep quality in this study were similar or even greater than that reported for cognitive behavioral intervention and other physical activity studies [18
]. Improvements were seen in global PSQI score and sleep duration, with most of the exercise group having a score of 5 or below following treatment, indicating good overall sleep quality. Compared to a 25 week Tai Chi study that reported a significant decrease in PSQI score of 1.8 points [39
], the current study achieved an average 4.8 point reduction in PSQI score. In a previous study, our group, reported a 1.1 drop in PSQI score for morning and a 1.5 drop for evening structured activity following two weeks of intervention [18
]. The larger effect seen in our study may be due to differences in the duration and intensity of the physical activity level and the characteristics of the participants.
The increase in self reported sleep duration by 1.25 hours in the exercise plus sleep hygiene education group is higher than what has been reported for other non-pharmacological interventions for insomnia [30
] This large increase in sleep duration may be in part due to the inclusion criteria of having a habitual sleep duration of less than 6.5 hours a night, which was verified with wrist actigraphy and sleep log. In addition, the elevated baseline WASO as measured by actigraphy and PSG indicate that this group of patients had sleep maintenance insomnia type. Thus, improved sleep continuity may also have contributed to the self reported increase in sleep duration.
There was also a significant reduction in the sleep latency sub-score of the PSQI but not in sleep latency measured as a continuous variable. This apparent difference could be because the PSQI sleep latency sub-score reflects both sleep latency and the frequency of being unable to fall asleep within 30 minutes [31
]. Therefore, while there may not have been a reduction in the actual time to fall asleep, there was likely a decrease in the number of times per week in which the participants experienced the problem.
It has been suggested that physical activity may improve sleep via improvements in depressive symptoms in those with depression [41
]. Consistent with this hypothesis, in our study, there was a significant association between improvements in depressive symptoms and improvements in subjective sleep quality in the whole group. However, the improvements in subjective sleep quality (PSQI score) associated with exercise remained after adjusting for depressive symptoms (CES-D score), indicating that the positive effect of exercise on sleep quality is also independent of depressive symptoms.
At baseline, SF-36 scores in this study were similar to those previously reported for people with mild-severe insomnia [42
]. One of the largest improvements following exercise intervention was observed in vitality, a high vitality score means that in the past 4 weeks the person feels full of “pep” and energy all the time [33
]. For the exercise group the vitality measure from the SF-36 improved substantially by 25.5 points following intervention compared to a 0.12 reduction for the non-physical activity group. In comparison with pharmacological therapies, in a study of the hypnotic eszopiclone over a 1-6 month period there was a 15 point increase in vitality [45
]. Furthermore, the degree of change in vitality in the current study was greater than the differences seen between people with insomnia and controls (16 points) or patients with depression and controls (13 points) [44
There was a positive relationship between improvements in sleep quality and improvements in fitness level as determined by maximum heart rate in the exercise group, although this was only a trend (p=0.058). However, a similar correlation between sleep quality and V02
max was not seen. This may in part be due to the limited ability of older adults to readily augment O2
uptake in response to exercise [46
]. These results suggest that the effect of exercise on sleep quality, mood and sleepiness may be mediated via mechanism other than only cardiopulmonary fitness.
There are several potential limitations in this study, including the reliance on self- reported sleep quality measures, the relatively small number of participants and the female preponderance of the sample. The baseline PSG parameters demonstrate relatively short sleep latencies and preserved slow wave sleep which may be in part due to the female preponderance of the sample and/ or the paradoxical effect of sleeping in the laboratory in patients with psychophysiological insomnia. Although the gender imbalance may affect the generalizability of the study, our findings remain relevant to patients with insomnia because insomnia is more prevalent among women than men [48
]. Another limitation was the higher dropout rate in the non-physical activity group. This may have been due in part to the desire of some participants to be randomized to the exercise condition. The internal validity of the study may be affected if those with low expectations for the non-physical activity intervention selectively dropped out after randomization.
However, these results are of clinical importance because self-reported measures of overall sleep quality, sleep latency, sleep duration, alertness and quality of life are the most widely used measure of insomnia treatment effectiveness in clinical practice. Therefore, the demonstration of the feasibility and ability of a program of exercise and sleep hygiene education to improve sleep quality in older adults with insomnia, together with the other known positive effects of physical activity on cardiopulmonary, metabolic and cognitive health, underscores the importance of incorporating structured physical activity in any comprehensive program for the management of insomnia in older adults.