[show abstract][hide abstract] ABSTRACT: Over the next 20 years the number of Americans diagnosed with dementia is expected to more than double (CDC, 2007). It is, therefore, an important public health initiative to understand what factors contribute to the longevity of a healthy mind. Both default mode network (DMN) function and increased aerobic fitness have been associated with better cognitive performance and reduced incidence of Alzheimer's disease among older adults. Here we examine the association between aerobic fitness, functional connectivity in the DMN, and cognitive performance. Results showed significant age-related deficits in functional connectivity in both local and distributed DMN pathways. However, in a group of healthy elderly adults, almost half of the age-related disconnections showed increased functional connectivity as a function of aerobic fitness level. Finally, we examine the hypothesis that functional connectivity in the DMN is one source of variance in the relationship between aerobic fitness and cognition. Results demonstrate instances of both specific and global DMN connectivity mediating the relationship between fitness and cognition. We provide the first evidence for functional connectivity as a source of variance in the association between aerobic fitness and cognition, and discuss results in the context of neurobiological theories of cognitive aging and disease.
[show abstract][hide abstract] ABSTRACT: Individuals with multiple sclerosis (MS) are less physically active than non diseased people. One method for increasing physical activity levels involves the identification of factors that correlate with physical activity and that are modifiable by a well designed intervention. This study examined two types of self-efficacy as cross-sectional and prospective correlates of objectively measured physical activity in 16 individuals with a diagnosis of MS. The participants completed two measures of self-efficacy and then wore an accelerometer for a 5-day period at baseline and then at 3 months follow-up. Self-efficacy for continued physical activity was associated with baseline and follow-up levels of physical activity. Self-efficacy for overcoming barriers was associated with follow-up levels of physical activity and change in physical activity across a 3-month period. Researchers should consider self-efficacy as a possible component of an intervention that is designed to increase physical activity levels in those with MS. International Journal of Rehabilitation Research
International journal of rehabilitation research. Internationale Zeitschrift fur Rehabilitationsforschung. Revue internationale de recherches de readaptation 10/2009; 32(3):260-3. · 0.36 Impact Factor
[show abstract][hide abstract] ABSTRACT: Deterioration of the hippocampus occurs in elderly individuals with and without dementia, yet individual variation exists in the degree and rate of hippocampal decay. Determining the factors that influence individual variation in the magnitude and rate of hippocampal decay may help promote lifestyle changes that prevent such deterioration from taking place. Aerobic fitness and exercise are effective at preventing cortical decay and cognitive impairment in older adults and epidemiological studies suggest that physical activity can reduce the risk for developing dementia. However, the relationship between aerobic fitness and hippocampal volume in elderly humans is unknown. In this study, we investigated whether individuals with higher levels of aerobic fitness displayed greater volume of the hippocampus and better spatial memory performance than individuals with lower fitness levels. Furthermore, in exploratory analyses, we assessed whether hippocampal volume mediated the relationship between fitness and spatial memory. Using a region-of-interest analysis on magnetic resonance images in 165 nondemented older adults, we found a triple association such that higher fitness levels were associated with larger left and right hippocampi after controlling for age, sex, and years of education, and larger hippocampi and higher fitness levels were correlated with better spatial memory performance. Furthermore, we demonstrated that hippocampal volume partially mediated the relationship between higher fitness levels and enhanced spatial memory. Our results clearly indicate that higher levels of aerobic fitness are associated with increased hippocampal volume in older humans, which translates to better memory function.
[show abstract][hide abstract] ABSTRACT: Dedifferentiation, or decreased processing specificity, has been suggested to represent a ubiquitous characteristic of cognitive aging. In this study, we examined both age-related differences and intra-group differences in neural specificity in the ventral visual cortex for color, words, faces and places. Our results demonstrated that neural dedifferentiation was not ubiquitous across stimulus categories. Neural dedifferentiation was also relatively stable, across age, in a group of older adults. Older adults with more overall gray matter showed less neural dedifferentiation in the visual cortex. However, regional gray matter volume was not associated with neural dedifferentiation. We illustrate these effects using a discriminability metric, a signal detection theory measure, for neural dedifferentiation that takes into account both magnitude and variance of brain activation. The dedifferentiation measure provides a quantitative means to examine activation patterns and individual difference factors associated with neural dedifferentiation, and to test theories of behavioral dedifferentiation in cognitive aging literature.
Brain research 10/2008; 1244:121-31. · 2.46 Impact Factor
[show abstract][hide abstract] ABSTRACT: In spite of consistent evidence to suggest that being more physically active is associated with enhanced quality of life (QOL), there have been remarkably few attempts to determine the possible underlying mechanisms in this relationship.
To prospectively examine the roles played by self-efficacy and physical and mental health status in the physical activity and QOL relationship in older women.
Older women (M age = 68.12 years) completed measures of physical activity, self-efficacy relative to balance, mental and physical health status, and global QOL at baseline (N = 249) and 24-month follow-up (N = 217). Demographics and general health information were assessed at baseline. A panel analysis within a covariance modeling framework was used to analyze the data.
Analyses indicated that changes in physical activity over time were associated with residual changes in self-efficacy. Changes in self-efficacy were significantly associated with residual changes in physical and mental health status. Only changes in mental health status were significantly related to residual changes in global QOL.
Results from this study support the role of self-efficacy in the relationship between physical activity and QOL. Future physical activity promotion programs should include strategies to enhance self-efficacy for physical activity to be most effective for this population.
Annals of Behavioral Medicine 09/2008; 36(1):13-20. · 4.20 Impact Factor
[show abstract][hide abstract] ABSTRACT: Physical inactivity is a major health problem in the United States, particularly in elderly and disabled populations. Little research exists examining the relationships between aspects of the built environment and physical activity in older adults and individuals with multiple sclerosis (MS). We adopted a social cognitive perspective to examine the independent roles of perceptions of the environmental, self-efficacy and functional limitations in understanding physical activity levels among elderly women and women with MS. Older women (n=136) and women diagnosed with MS (n=173) were recruited to participate in separate cross-sectional studies. Individuals completed a battery of questionnaires and wore an activity monitor for 7 days. All measures were issued and collected through the mail with the use of self-addressed, pre-paid envelopes. Initial correlational analyses indicated that self-efficacy, functional limitations and environmental perceptions were significantly related to physical activity. Among older women, self-efficacy, functional limitations and street connectivity demonstrated independent contributions to physical activity behavior. Only self-efficacy and functional limitations demonstrated significant associations among women with MS. The prospective contributions of the environment and individual factors to changes in physical activity need to be determined.
Health Education Research 09/2008; 23(4):744-52. · 1.66 Impact Factor
[show abstract][hide abstract] ABSTRACT: The relationships between self-efficacy (SE), i.e., beliefs in personal capabilities, and behavioral and neuroelectric (i.e., ERN, Pe) indices of action monitoring were investigated in 40 older adults (13 male) during the completion of a flanker paradigm performed under task conditions emphasizing either accuracy or speed. SE relative to task performance during both conditions was assessed prior to each cognitive task. Results indicated that high-SE older adults exhibited larger ERN and Pe amplitudes compared to low-SE older adults under the accuracy instruction condition. Additionally, a moderating effect of SE on the relationship between ERN and post-error response accuracy was revealed in the accuracy condition, with greater ERN amplitude associated with greater post-error accuracy in the high-SE group. No significant relationships were evident between ERN and post-error accuracy in the low-SE group. Further, no significant relationships involving SE were observed in the speed condition. The findings suggest that SE may be related to neuroelectric and behavioral indices of action monitoring in older adults when task demands require greater attention to action monitoring processes.
Neurobiology of aging 08/2008; 29(7):1111-22. · 5.94 Impact Factor
[show abstract][hide abstract] ABSTRACT: Perceptions of one's environment and functional status have been linked to physical activity in older adults. However, little is known about these associations over time, and even less about the possible mediators of this relationship. We examined the roles played by neighborhood satisfaction, functional limitations, self-efficacy, and physical activity in a sample of older women over a 6-month period.
Participants (N = 137, M age = 69.6 years) completed measures of neighborhood satisfaction, functional limitations, self-efficacy, and physical activity at baseline and again 6 months later.
Analyses indicated that changes in neighborhood satisfaction and functional limitations had direct effects on residual changes in self-efficacy, and changes in self-efficacy were associated with changes in physical activity at 6 months.
Our findings support a social cognitive model of physical activity in which neighborhood satisfaction and functional status effects on physical activity are in part mediated by intermediate individual outcomes such as self-efficacy. Additionally, these findings lend support to the position that individual perceptions of both the environment and functional status can have prospective effects on self-efficacy cognitions and ultimately, physical activity behavior.
International Journal of Behavioral Nutrition and Physical Activity 02/2008; 5:13. · 3.58 Impact Factor
[show abstract][hide abstract] ABSTRACT: To examine the hypothesis that changes in self-efficacy and functional performance mediate, in part, the beneficial effect of physical activity on functional limitations over time.
Prospective, observational study.
Two hundred forty-nine community-dwelling older women.
Participants completed measures of self-reported physical activity, functional limitations, and self-efficacy. Four measures of physical function performance were also assessed. Measures were completed at baseline and 24 months. Data were analyzed using a panel model within a covariance modeling framework.
Results indicated that increases in physical activity over time were associated with greater improvements in self-efficacy, which was associated in turn with improved physical function performance, both of which mediated the association between physical activity and functional limitations. Fewer functional limitations at baseline were also associated with higher levels of self-efficacy at 24 months. Age, race, and health status covariates did not significantly change these relationships.
The findings support the mediating roles of self-efficacy and physical function performance in the relationship between longitudinal changes in physical activity and functional limitations in older women.
Journal of the American Geriatrics Society 01/2008; 55(12):1967-73. · 3.98 Impact Factor
[show abstract][hide abstract] ABSTRACT: Individuals with multiple sclerosis (MS) are more sedentary than the general population, increasing their propensity for reduced functional ability, mobility, and activities of daily living. Self-efficacy has been one of the most consistent determinants of physical activity across populations, including those with MS. However, no studies exist that have attempted to influence self-efficacy in MS patients, in an effort to improve physical activity participation. We conducted a three-month randomised, controlled trial (n=26), contrasting the effects of an efficacy-enhancement exercise condition and a control exercise condition on exercise adherence, well-being, and affective responses to exercise. Analyses indicated that individuals in the efficacy enhancement condition attended more exercise sessions, reported greater levels of well-being and exertion, and felt better following exercise than individuals in the standard care condition. Regardless of treatment condition, individuals with a stronger sense of exercise self-efficacy, who reported more enjoyment following the exercise sessions, demonstrated significantly greater adherence with the exercise program. We believe this to be the first empirical attempt to change physical activity behavior in persons with MS using a well-established theoretical framework to drive the intervention. Continued examination of self-efficacy as a determinant of behavior change in individuals with MS is needed.
[show abstract][hide abstract] ABSTRACT: To examine the contribution of social-cognitive factors (self-efficacy and affect) in predicting long-term physical activity in a sample of older adults (N=174).
A prospective design assessed physical activity and psychosocial variables at 2 and 5 years following a 6-month randomized, controlled exercise trial.
The primary outcome variable was self-reported physical activity, with previous behavior, self-efficacy, and affect assessed as determinants of physical activity.
Covariance modeling analyses indicated that physical activity at Year 2 was the strongest predictor of physical activity at 5-year follow-up. Both self-efficacy and affect at Year 2 were also associated with physical activity at Year 5, as was original treatment condition. Variables accounted for 35% of the variance in Year 5 activity.
Older adults with higher levels of physical activity, more positive affect, and higher self-efficacy at Year 2 were more likely to continue to be active at Year 5. This study is one of the longest follow-ups of exercise behavior in older adults and has implications for structuring environments to maximize the maintenance of physical activity.
Health Psychology 06/2007; 26(3):375-80. · 3.83 Impact Factor
[show abstract][hide abstract] ABSTRACT: Biomedical advances and the practice of preventive health behaviors have resulted in an unprecedented growth in the older population of the United States, a trend projected to continue during the next several decades. However, the addition of years to life is no guarantee that those years will be quality years. There is growing evidence to suggest that physical activity is a behavioral modality that is consistently associated with quality of life outcomes. However, there are numerous conceptual, theoretical, and definitional ambiguities associated with this literature. In this review, we examine the literature on physical activity and quality of life in older adults. Specifically, attention is given to the conceptualization of quality of life in the medical and psychological disciplines and how these differential viewpoints influence the outcomes measured and the nature of the relationships reported. We also address the question of whether a dose-response relationship exists between these constructs, as well as the extent to which physical activity is associated with important aspects of cognitive, physical, and psychosocial function. Finally, we propose a multidimensional model for examining the potential mediating and moderating factors in the physical activity and quality-of-life relationship and discuss the practical implications that such a model has for practitioners.
American Journal of Lifestyle Medicine 01/2007; 1(5):389-396.
[show abstract][hide abstract] ABSTRACT: This study examined the role of self-efficacy and physical function performance in the relationship between physical activity and functional limitations. Older women (age, M = 68.2 years) completed measures of physical activity, self-efficacy, physical function performance, and functional limitations at the baseline of an ongoing study. Analyses indicated that physical activity was associated with self-efficacy for exercise, efficacy for gait and balance, and physical function performance. Both measures of efficacy and physical functional performance were associated with functional limitations. Demographic and health status variables did not differentially influence these relationships. Although cross-sectional in nature, our findings suggest that physical activity, self-efficacy, and functional performance may all play a role in reducing functional limitations. Of particular relevance is the fact that both physical activity and self-efficacy represent important, modifiable factors that can enhance function.
The Journals of Gerontology Series B Psychological Sciences and Social Sciences 10/2006; 61(5):P270-7. · 3.01 Impact Factor
[show abstract][hide abstract] ABSTRACT: Physical activity has been positively linked to quality of life (QOL) in older adults. Measures of health status and global well-being represent common methods of assessing QOL outcomes, yet little has been done to determine the nature of the relationship of these outcomes with physical activity.
We examined the roles played by physical activity, health status, and self-efficacy in global QOL (satisfaction with life) in a sample of older Black and White women.
Participants (N = 249, M age = 68.12 years) completed multiple indicators of physical activity, self-efficacy, health status, and QOL at baseline of a 24-month prospective trial. Structural equation modeling examined the fit of 3 models of the physical activity and QOL relationship.
Analyses indicated that relationships between physical activity and QOL, self-efficacy and QOL were all indirect. Specifically, physical activity influenced self-efficacy and QOL through physical and mental health status, which in turn influenced global QOL.
Our findings support a social cognitive model of physical activity's relationship with QOL. Subsequent tests of hypothesized relationships across time are recommended.
Annals of Behavioral Medicine 03/2006; 31(1):99-103. · 4.20 Impact Factor
[show abstract][hide abstract] ABSTRACT: The recent development of the Late-Life Function and Disability Instrument (LL-FDI) was an important contribution to the measurement of function and disability in older adults. The present study examined the psychometric properties and construct validity of the LL-FDI measure in a sample of older women.
Older black (n = 81) and white (n = 168) women completed the LL-FDI, several measures of physical function, and physical activity measures, and had their body mass index assessed at baseline of an ongoing prospective study. Confirmatory factor analyses (CFA) and correlational analyses were used to examine factorial and construct validity of the measure.
The CFA, using an iterative model modification technique, resulted in an acceptable 15-item solution for the function component and an 8-item solution for the disability component. This abbreviated instrument demonstrated high correlations with the original scales. Construct validity for the LL-FDI was supported. Participants who demonstrated better physical function, reported being more active, and had lower body mass index reported less disability and less difficulty with function on the LL-FDI.
The LL-FDI appears to be an effective instrument for assessing function and disability in older women, and the abbreviated version reported here may prove useful in certain circumstances due to its brevity. However, continued determination of the construct validity of the complete and abbreviated scales is recommended.
The Journals of Gerontology Series A Biological Sciences and Medical Sciences 08/2005; 60(7):901-9. · 4.31 Impact Factor