Walking stabilizes cognitive functioning in Alzheimer's disease (AD) across one year
Introduction
AD is a public health issue affecting every 1 in 8 Americans who are 65 years and older and nearly half of all Americans aged 85 years and older. In California alone, roughly 480,000 individuals were affected in 2010 and this number is expected to increase by 50% in the next 15 years (Thies, Bleiler, & Alzheimer's Association, 2011). AD has devestating consequences for both the diagnosed individual and the entire family, because it impairs cognitive-behavioral functioning and disrupts activities of daily living (ADL; Melrose et al., 2011, Rolland et al., 2007). Given the significant emotional and financial toll AD has on the individual, family, and society, identifying promising treatment strategies is imperative, in order to reduce the risk, slow the decline and alleviate symptoms in AD.
Exercise is one such promising strategy. Several epidemiological studies involving older adults have suggested that physical activity may slow the progression of cognitive decline (Larson, 2010, Yu et al., 2006), improve performance on tests of cognition and mood (Angevaren et al., 2008, Antunes et al., 2005, Vogt et al., 2010, Weuve et al., 2004, Williams and Tappen, 2007), and enhance sleep quality (Benloucif et al., 2004). Consistent with these epidemiological studies, a limited number of clinical trials have linked increased physical activity in healthy elderly adults to improved cognition, particularly executive functioning (Colcombe et al., 2003, Colcombe and Kramer, 2003, Colcombe et al., 2004, Kramer et al., 2003, van Gelder et al., 2004). Human epidemiological, clinical and neuroimaging studies are supported by animal research which has showed enhanced cerebral function through the upregulation of neurotrophic factors (Cotman, Berchtold, & Christie, 2007), increased neurogenesis (Pereira et al., 2007, van Praag et al., 1999, van Praag et al., 2005), increased blood flow (Pereira et al., 2007), and reduced oxidative stress (Kiraly & Kiraly, 2005), as well as reduced β-amyloid (Adlard, Perreau, Pop, & Cotman, 2005) in response to exercise. Taken together, these findings support the premise that exercise has beneficial effects on cognition and brain function.
Exercise benefits on cognition are also supported by the results of controlled trials in normal aging. A recent meta-analysis showed an overall benefit of aerobic exercise on episodic memory, attention, processing speed and executive function in non-demented older adults (Smith et al., 2010). To date, the results of 2 randomized controlled trials provide preliminary support for a potential cognition-enhancing effect of aerobic exercise in adults with Mild Cognitive Impairment (MCI). Lautenschlager et al. (2008) showed that 6 months of home-based exercise vs. usual care improved performance on well-established measures of global cognition, e.g., the AD Assessment Scale for Cognition. In the second study, Baker et al. (2010) observed that 6 months of structured and supervised aerobic exercise vs. stretching exercise improved executive function in sedentary adults with MCI. In people with dementia, several studies support a possible role of physical activity on improved cognitive function, slowed disease course and improved ADL (Heyn et al., 2004, Rolland et al., 2007, Scarmeas et al., 2010, Venturelli et al., 2011). However, the field is still in the developmental stage and there is no clear consensus. Since physical activity may slow the onset of age-related cognitive decline and improve cognition in MCI, the possibility exists that exercise could also improve cognition and/or reduce the rate of decline in mild-to-moderate AD. If this is the case, then those individuals who are physically active might show a slower rate of decline than those who are sedentary.
In order to evaluate whether physical activity may affect cognitive decline in AD, we surveyed a sample of AD patients evaluated at nine outpatient clinics across the state of California. This study had two objectives: (1) to quantify the prevalence, type, and amount of physical activity (measured by the YALE in total hours per week; e.g., the dependent variable of interest) in mild-to moderate-AD patients seen at the Alzheimer's Research Centers of California (ARCC), now called the California Alzheimer's Disease Centers (CADC), and (2) to determine whether those participants who engaged in physical activities showed altered global cognition, functional capacity and/or mood states compared to those who were more sedentary. To this end, patients and their informants, were surveyed at baseline and after 1 year (1 year) to determine the prevalence and type of exercise activity participants engaged in. Here, the total number of hours engaged in physical activity was examined, and then that amount of activity (as measured by the YALE) was evaluated with respect to performance on a set of global cognitive (MMSE), affective (POMS), behavioral (GDS, NPI), and functional (BRDRS, FAQ) evaluations, in order to elucidate whether any correlations existed among these variables.
Section snippets
Setting: The Alzheimer's Disease Research Centers of California
Statewide, California has 10 ARCCs, 9 of which were involved in recruiting the cognitively impaired participants and their informants for this study. Located in outpatient clinics at large university medical centers, the ARCCs receive funding through the California Department of Public Health and collect a common set of demographic, diagnostic, and medical data (i.e., Minimum Uniform Data Set (MUDS)) on each participant. Key clinical personnel at each of the ARCC sites participate in
Characteristics of the population and results at baseline
The California AD study sample (N = 104) included older adults aged 63–98 (Mean: 81 ± 6.54) with an average of 16.67 years of education (±3.25 years). Approximately half the study participants were female (44.2%) and the sample included primarily Caucasian American (69.8%) and Latino/Hispanic Americans (20.1%; see Table 1).
Discussion
The objective of the current study was to quantify the prevalence of physical activity in AD patients, and to investigate whether those participants who engaged in physical activities over a 1-year interval showed altered affect/mood states, IADL performance or cognitive function as compared to those who were more sedentary. The sample consisted of males and female AD patients, who were well educated (16.67 ± 3.25 years) and were primarily Caucasian and Latino-Hispanic Americans. Analyses
Conclusions
Our study concludes that a sedentary lifestyle correlates with a decline in cognitive function, a loss of vigor, and an increase in feelings of anger, confusion, depression and fatigue. We also conclude that some level of physical activity, especially walking, is beneficial to cognitive function in those with mild-to-moderate AD. This study supports the premise that walking activities may be one intervening strategy that could be useful in AD populations, and that future structure AD clinical
Conflict of interest statement
The current study has no conflicts of interest to report.
Acknowledgements
We wish to acknowledge the efforts of the Clinical Staff from the various CADC, ADRC and ARCC sites across the state of California. This study was funded by the California Alzheimer's Disease Centers and the following grants: 5P50AG016573, 3P50AG016573, and 5P01AG000538-32.
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