NATIONAL HARBOR, MD. – A pair of studies by the same research team has clarified how poor sleep worsens cognitive and physical function in people with multiple sclerosis (MS) and how poor sleep can be improved by exercise.
Whether the better sleep directly relates to the cognitive and physical improvements was not shown conclusively. However, a link between exercise and transient cognitive improvement has been demonstrated by others.
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“Exercise may be a nonpharmacological and an inexpensive method to address sleep symptoms,” said Catherine Siengsukon, Ph.D., of the University of Kansas Medical Center, Kansas City, at the annual meeting of the Consortium of Multiple Sclerosis Centers.
About half of all people with MS experience poor sleep that results from the disease itself, medications, anxiety/depression, or other causes. The fatigue and reduced physical and psychological function diminish the quality of life and can increase the risk of mortality. “But it is unknown if poor sleep quality may impact physical function in individuals with MS,” said Dr. Siengsukon.
In healthy individuals, cognitive aspects like attention, working and long-term memory, information processing, decision making, and problem solving can all be affected by poor sleep. “But which cognitive domains are associated with poor sleep quality in people with MS is unknown,” said Dr. Siengsukon.
In the first study, 40 people (36 females) with MS (mainly relapsing-remitting MS) were analyzed through a battery of established tests of sleep quality, cognitive function, physical function, depression, anxiety, and quality of life. The subjects had a disease duration of about 12 years. All were ambulatory without the need of assistance, and none had sleep apnea.
About 68% of the subjects were considered poor sleepers with the remainder being good sleepers. They were comparable in age, sex, type of MS, disease duration, and cognitive impairment.
Compared with good sleepers, poor sleepers were significantly impaired in visuospatial memory and questionnaire-assessed physical function, were more fatigued, were more prone to be anxious and depressed, and had a worse quality of life. Independent factors of poor sleep quality included state and trait anxiety (P = .003 and .02, respectively).
“Evidence demonstrates that sleep consolidates memory. Therefore, poor sleep may selectively impair memory while not impacting other cognitive domains,” said Dr. Siengsukon.
In the second study, the influence of supervised, moderate exercise and home exercise on sleep quality was assessed in 22 other MS patients. Most had relapsing-remitting MS. The inclusion and exclusion criteria were similar to those for the first study, with additional exclusion criteria concerning cardiovascular risk of exercise.
The supervised stretching and exercise program for 12 subjects was done at a social center and utilized recumbent exercise machines, with the home-based program for 10 subjects consisting of stretching and outdoor walking. Both exercise programs were done three times weekly for 12 weeks.
Both exercise programs were beneficial in improving sleep, with the moderate-intensity program being relatively more effective than home-based exercise in two measurement scales of sleep. The greater benefit of moderate exercise might reflect the mode of exercise, with subjects feeling safer and more relaxed using a recumbent exerciser, Dr. Siengsukon said. Offering the exercise in a social setting might have been another plus.
“The results suggest that moderate-intensity exercise may improve cardiovascular fitness in people with MS. While both groups experienced moderate to large effects on sleep quality, the mechanism for improvement in sleep quality remains to be determined, as the improvement was not related to change in cardiorespiratory fitness,” said Dr. Siengsukon.
A link between treadmill exercise and transient cognitive improvement has been reported.
The studies were supported by the National Institutes of Health and the National Multiple Sclerosis Society. Dr. Siengsukon disclosed grant support from the National Multiple Sclerosis Society.