Exercise Improves Cognition, Daily Activities in Dementia

Pauline Anderson

December 04, 2013

Exercise may improve cognitive function and the ability to perform activities of daily living in people with dementia, a new Cochrane review has found.

The results suggest that it's time to prescribe physical activity for patients with dementia, according to the study's lead author, Dorothy Forbes, PhD, associate professor, Faculty of Nursing, University of Alberta, Edmonton, Canada.

"We can't tell them exactly what strength or what type or how often it should be done because the evidence isn't clear yet, but this definitely suggests that physical activity does delay cognition and activities of daily living impairments, and that alone tells us that it's important to be encouraging physical activity for this population."

However, the review found no significant effect of exercise on challenging behaviors or levels of depression among patients with dementia.

The review was published online December 3 in the Cochrane Library.

Updated Review

The new analysis updates a previous Cochrane review in 2008 that included 4 randomized controlled trials but only 2 that provided the data necessary for the intended analysis. That review concluded that there was insufficient evidence to permit conclusions about the effectiveness of physical activity programs in improving cognition, function, behavior, depression, or mortality in people with dementia. Since then, further studies of the effect of exercise on dementia have been conducted.

Dr. Dorothy Forbes

For this new review, researchers searched ALOIS, the Cochrane Dementia and Cognitive Improvement Group's Specialized Registry. The updated analysis included 16 trials, published between 1997 and 2012, 4 of which were conducted in the United States; 2 in France; 2 in the Netherlands; and 1 each in Sweden, Belgium, Brazil, South Korea, and Spain.

The included studies include a total of 937 participants, mostly older people with Alzheimer's disease (AD) living in nursing homes, graduated residential care, or psychiatric facilities.

All but 1 trial required a diagnosis of dementia, with the most commonly used diagnostic criteria being from the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders. Several studies used the Mini-Mental State Examination to assess cognition, but some also used the Cognitive Memory Performance Scale, the Rapid Evaluation of Cognitive Function Test, or the Delayed Recall score using the Eight Words Test.

Researchers in the various studies assessed activities of daily living (ADLs) using the Barthel ADL Index or the Changes in Advanced Dementia Scale. They evaluated depression with the Montgomery-Asberg Depression in Dementia, Cornell Scale for Depression in Dementia, the Neuropsychiatric Inventory, or the Geriatric Depression Scale. And they assessed caregiver burden using the Screen for Caregiver Burden or the Zarit Burden Interview Scale.

None of the studies measured participant or caregiver mortality, caregiver quality of life, or use of healthcare services.

Ten trials specified the participants' level of physical activity. For example, 1 trial required that participants be able to walk short distances with no aid, another required no apparent disability in hand motor function, and another required the ability to walk 10 meters without technical assistance.

Exercise Frequency

Exercise programs ranged in frequency (twice a week; 3, 4, or 5 times a week; or daily), duration (2 weeks to 12 months), and type (hand movements, walking, upper- and lower-limb exercises). In 3 trials, the exercises were performed while seated to accommodate people in wheelchairs.

Control groups ranged from those receiving usual care with no additional intervention to those that included social contact, or social contact with additional activities, such as films, singing, and reading.

In 8 trials (with 329 participants) that examined the effect of exercise on cognition, the analysis revealed significant results (P = .04) that favored the exercise program (standardized mean difference [SMD], 0.55, 95% confidence interval, 0.02 - 1.09). However, there was substantial unexplained heterogeneity, and when the only trial that included just participants with moderate to severe dementia was excluded, the heterogeneity was reduced somewhat but the results were no longer significant.

There was also unexplained statistical heterogeneity in the analysis looking at the effect of exercise on ADLs that included 6 trials (with 289 participants). Here, there were also significant results (P = .03) that favored the exercise program (SMD, 0.68; 95% CI, 0.08 - 1.27).

The unexplained heterogeneity suggests there are "still a lot of unknowns," and therefore the results pertaining to cognition and ADLs should be interpreted with caution, said Dr. Forbes.

Only 2 of the studies were carried out in the home setting. One that included 40 participants found that when informal caregivers supervise a loved one in an exercise program, the caregiver burden may be reduced. "Much more work needs to be done looking at those living at home because most people do live at home," commented Dr. Forbes.

Challenging Behaviors

The new review found no significant effect of exercise on challenging behaviors or depression in patients with dementia. "There just was not enough evidence out there to be able to determine a positive effect," said Dr. Forbes. "We need more research in this area to say conclusively that it doesn't or it does impact challenging behaviors and depression."

Because the analysis didn't separate out different types of dementia, it's unclear whether physical activity has a stronger impact on AD, vascular dementia, or frontal lobe dementia. However, according to Dr. Forbes, there is some suggestion in the literature that exercise has a greater impact on AD.

"Again, we just need more trials to be able to tease out what type of dementia is best for which type of exercise: aerobic, strength, and/or balance," she said.

Past research has suggested that exercise provides a powerful stimulus that can counteract the molecular changes that underlie the progressive loss of hippocampal function, said the authors. Studies have shown that physical activity improves vascular health by reducing blood pressure, arterial stiffness, oxidative stress, and systematic inflammation. All these factors are linked to the maintenance of cerebral perfusion (ie, the balance between the supply and demand of nutrients to the brain).

As well, insulin resistance or glucose intolerance is linked with amyloid-β plaque formation, a feature of AD. Exercise enhances insulin sensitivity and glucose control; preserves neuronal structure; and promotes neurogenesis (formation of nerve cells), synaptogenesis (gaps between nerve cells), and capillarization (formation of blood vessels).

Dr. Forbes and her colleagues plan to carry out another review in the next 6 months. "It's an area that has huge interest, so there are a lot more trials coming along," she said.

In 2012, the World Health Organization declared dementia to be a public health priority. As the population ages, the number of people with dementia living in the community will rise dramatically over the coming decades. Practice guidelines currently recommend exploring behavioral and psychological interventions before exploring pharmacologic ones because of the limited benefit of drug treatments.

The authors have disclosed no relevant financial relationships.

Cochr Database Syst Rev. Published online December 3, 2013. Abstract

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