The authors investigated the role of exercise training in the management of sleep apnea by entering nine patients with mild to moderate OSAS (Obstructive Sleep Apnea Syndrome) who completed a six month supervised exercise program. Prior to, and at the end of, this program, they conducted sleep studies, body measurements, and questionnaire evaluation of quality of life, daytime sleepiness and mood.
Their subjects included mostly men, ages 32 to 60 years (average 48 years of age), of normal to moderately overweight body mass indices (less than 40), in good general health, with current symptoms of OSAS and sleep study evidence of OSAS (AHI over 5 respiratory arousals per hour of sleep). Five were using nasal CPAP (continuous positive airway pressure) throughout the study, starting one week to six months prior.
The exercise program consisted of three times per week of at least 20 minutes of individually designed, low impact, moderate aerobic exercise designed to elevate the heart rate up to 85% of the age-predicted maximum. This was gauged on the basis of an initial submaximal exercise treadmill test. Mostly the exercise consisted of treadmill walking and stationary cycling, complemented by stair climbing, rowing machines, and resistive weight exercises. Two subjects started the program but dropped out.
Subjects also received one session with a dietician at the beginning of the program, resulting in instruction for a balanced diet using the food pyramid paradigm designed to accomplish a 0.5-1.0 kg loss of weight each week.
The authors found a number of sleep study measures indicating improvement in sleep apnea during the course of this program: the Apnea Hypopnea Index (number of arousals from sleep associated with apneas or hypopneas, per hour), total sleep time, sleep efficiency (proportion of time in bed spent asleep), number of awakenings per hour, and number of arousals (lightening of sleep short of full consciousness) per hour. Following training, all subjects showed a decrease in AHI, two to within the normal range of less than 5, four less than 10. This did not correlate with exercise intensity or compliance, or with weight loss. No significant differences were observed between those subjects using CPAP and those without CPAP.
Other measures that showed improvement included weight (average weight loss=6.2 kilograms), self-rated quality of life, mood, and daytime sleepiness. Physical conditioning measured by physical work capacity increased and blood pressures decreased. Subjects averaged a compliance rate of 88% with the exercise program, ranging from 55% to 100%.
The authors noted that poor physical fitness, as well as upper body obesity, were significant risk factors for OSAS. Weight loss is often recommended as one strategy to help control the disease. However, there is little data on the relationship of exercise and improvement in physical conditioning to apnea severity.
They also noted that, while their subjects did lose weight, the amount lost was less than that generally considered necessary for an impact on sleep apnea. However, they admitted the possibility that the necessary weight loss had been overestimated.
They suggested another explanation for improvement in terms of improved ventilation, as a result of increased strength and endurance of the muscles responsible for breathing.
They concluded that such an exercise program might represent a useful adjunct (added measure) in the management of sleep apnea--though it did not appear to represent an adequate treatment measure by itself.
Regular exercise has long had a place in the rules of good sleep hygiene, aimed primarily at people with insomnia. Its application to obstructive sleep apnea is somewhat novel, but quite credible. Improved physical conditioning seems likely to benefit people with a host of varied diseases.
However, the study has two major flaws, which the well-informed lay reader should be capable of picking up.
The first flaw is the very small size of the study group. This problem is common to a great many studies, since acquiring subjects and maintaining them on a lengthy, complex study program requires a lot of time, effort, and usually money as well. However, it has the adverse effect of greatly limiting the conclusions that can be drawn from statistical analyses. For example, a comparison of the results of exercise training on 4 subjects using CPAP versus 5 without CPAP is predictably unlikely to show any significant differences simply because of the small numbers of subjects being compared. Similarly, correlations between factors like improvement in apnea and change in weight are greatly hindered by the size of the group.
The second flaw, also a common one, is the lack of any kind of control group of subjects who do not receive the exercise program but do have the same assessments at the same time periods. Why is this important, when apnea has shown a pattern of worsening over time, not improvement on its own? For one thing, most people, suffering from numerous and varied diseases, show improvement merely as the result of the attention afforded by participation in a study. A control group could be given still more equivalent attention by having them participate in some other program less likely to yield improvement in cardiorespiratory conditioning, such as simple weight lifting. Without a control group, it is hard to be sure that the intervention on which the authors focus really represents the most important causative factor in any changes observed.
That said, I want to repeat my earlier statement, that the results seem quite believable on general principles. However, they also give rise to concerns about how they will be used by clinicians.
"Preserve me from unseasonable and immoderate sleep."
Dr. Samuel Johnson, 1709-1784
For more information on Sleep Apnea, please see our Sleep Apnea Section.