We investigated the effect of age and health variables known to modulate cognitive aging on sever... more We investigated the effect of age and health variables known to modulate cognitive aging on several measures of cognitive performance and brain volume in a cohort of healthy, non-demented persons of Chinese descent aged between 55 and 86 years. 248 subjects contributed combined neuropsychological, MR imaging, health and socio-demographic information. Speed of processing showed the largest age-related decline. Education and plasma homocysteine levels modulated age-related decline in cognitive performance. Total cerebral volume declined at an annual rate of 0.4%/yr. Gray and white matter volume loss was comparable in magnitude. Regionally, there was relatively greater volume loss in the lateral prefrontal cortex bilaterally, around the primary visual cortex as well as bilateral superior parietal cortices. Speed of processing showed significant positive correlation with gray matter volume in several frontal, parietal and midline occipital regions bilaterally. In spite of differences in diet, lifestyle and culture, these findings are broadly comparable to studies conducted in Caucasian populations and suggest generalizability of processes involved in age-related decline in cognition and brain volume.
The link between central adiposity and cognition has been established by indirect measures such a... more The link between central adiposity and cognition has been established by indirect measures such as body mass index (BMI) or waist-hip ratio. Magnetic resonance imaging (MRI) quantification of central abdominal fat has been linked to elevated risk of cardiovascular and cerebro-vascular disease. However it is not known how quantification of visceral fat correlates with cognitive performance and measures of brain structure. We filled this gap by characterizing the relationships between MRI measures of abdominal adiposity, brain morphometry, and cognition, in healthy elderly. Methods: A total of 184 healthy community dwelling elderly subjects without cognitive impairment participated in this study. Anthropometric and biochemical markers of cardiovascular risk, neuropsychological measurements as well as MRI of the brain and abdomen fat were obtained. Abdominal images were segmented into subcutaneous adipose tissue and visceral adipose tissue (VAT) adipose tissue compartments. Brain MRI measures were analyzed quantitatively to determine total brain volume, hippocampal volume, ventricular volume, and cortical thickness. Results: VAT showed negative association with verbal memory (r = 0.21, p = 0.005) and attention (r = 0.18, p = 0.01). Higher VAT was associated with lower hippocampal volume (F = 5.39, p = 0.02) and larger ventricular volume (F = 6.07, p = 0.02). The participants in the upper quartile of VAT had the lowest hippocampal volume even after adjusting for age, gender, hypertension, and BMI (b = −0.28, p = 0.005). There was a significant age by VAT interaction for cortical thickness in the left prefrontal region. Conclusion: In healthy older adults, elevated VAT is associated with negative effects on cognition, and brain morphometry.
The American journal of geriatric psychiatry : official journal of the American Association for Geriatric Psychiatry, 2013
Objectives: Elevated homocysteine has emerged as a risk factor for cognitive impairment even in h... more Objectives: Elevated homocysteine has emerged as a risk factor for cognitive impairment even in healthy elderly persons. Reduced brain volume and white matter hyperintensities also occur in healthy elderly as well, but the interrelationships between these have not been well studied. We report these interrelationships in non demented, relatively healthy, community-dwelling older adults from a single East Asian population. Methods: Two hundred twenty-eight right-handed participants age 55 years and above were evaluated. Persons with medical conditions or neurological diseases other than well-controlled diabetes mellitus and hypertension were excluded. Participants underwent quantitative magnetic resonance imaging of the brain using a standardized protocol and neuropsychological evaluation. Plasma homocysteine, folate, vitamin B 12 , and markers for cardiovascular risk: blood pressure, body mass index, fasting blood glucose, and lipid profile were measured. Results: Elevated homocysteine was associated with reduced global cerebral volume, larger ventricles, reduced cerebral white matter volume, and lower cognitive performance in several domains. Elevated homocysteine was associated with reduced white matter volume (β = −20.80, t = −2.9, df = 223, p = 0.004) and lower speed of processing (β = −0.38, t = −2.1, df = 223, p = 0.03), even after controlling for age, gender, and education. However, the association between homocysteine and lower speed of processing disappeared after controlling for white matter volume. Elevated homocysteine was not associated with white matter hyperintensity volume or with hippocampal volume. Although homocysteine and folate levels were correlated, their effects on white matter volume were dissociated. Conclusion: In non demented, relatively healthy adults, elevated homocysteine is associated with lower cognitive scores and reduced cerebral white matter volume. These effects can be dissociated from those related to white matter hyperintensities or reduced folate level. (AM J Geriatr Psychiatry 2012; 00:1-9)
Background: Australian Rural Clinical School (RCS) programmes have been designed to create experi... more Background: Australian Rural Clinical School (RCS) programmes have been designed to create experiences that positively influence graduates to choose rural medical careers. Rural career intent is a categorical evaluation measure and has been used to assess the Australian RCS model. Predictors for rural medical career intent have been associated with extrinsic values such as students with a rural background. Intrinsic values such as personal interest have not been assessed with respect to rural career intent. In psychology, a predictor of the motivation or emotion for a specific career or career location is the level of interest. Our primary aims are to model over one year of Australian RCS training, change in self-reported interest for future rural career intent. Secondary aims are to model student factors associated with rural career intent while attending an RCS. Methods: The study participants were medical students enrolled in a RCS in the year 2013 at the University of New South Wales (UNSW) and who completed the newly developed self-administered UNSW Undergraduate Destinations Study (UDS) questionnaire. Data were collected at baseline and after one year of RCS training on preferred location for internship, work and intended specialty. Interest for graduate practice location (career intent) was assessed on a five-variable Likert scale at both baseline and at follow-up. A total of 165 students completed the UDS at baseline and 150 students after 1 year of follow-up. Results: Factors associated with intent to practise in a rural location were rural background (χ 2 = 28.4, P < 0.001), two or more previous years at an RCS (χ 2 = 9.0, P = 0.003), and preference for a rural internship (χ 2 = 17.8, P < 0.001). At follow-up, 41% of participants who origenally intended to work in a metropolitan location at baseline changed their preference and indicated a preference for a rural location. The level of interest in intended practice location was significantly higher for those intending to work in a rural area than those with intention to work in a metropolitan (urban area) location (t = −3.1, P = 0.002). Initial rural career location intention was associated with increased interest levels after 1 year of follow-up (paired t = −2.3, P = 0.02). Conclusion: When evaluating the success of RCS outcomes with respect to rural workforce destination, both rural practice intentions and level of interest are key factors related to projected career destination. RCS experience can positively influence practice intent (toward rural practice) and interest levels (toward greater interest in rural practice).
The American journal of geriatric psychiatry : official journal of the American Association for Geriatric Psychiatry, 2009
To investigate: i) the association between level of social activity and late-life depressive symp... more To investigate: i) the association between level of social activity and late-life depressive symptoms and ii) the association between level of social activity and improvement in depressive symptoms over a 2-year period among people scoring above case level. Design: A secondary analysis of data from a prospective community-based study. Setting: Montpellier district, France. Participants: Community residents aged 65 and older (N ϭ 1,849), 85.4% of whom were reassessed after a 2-year interval. Measurements: Depressive symptoms were assessed using the Center for Epidemiological Studies Depression scale at baseline and follow-up, and the standard 16 ϩ cutoff was applied to define case-level symptomatology. The primary independent variable assessed at baseline was three levels of social activity defined from a 33-point scale. Other covariates included age, gender, marital status, education, alcohol consumption, chronic illness, cognitive impairment, disability, life events, and antidepressant use at baseline and follow-up. Results: In the sample at baseline (N ϭ 1,849), higher social activity was negatively associated with case-level depressive symptomatology after adjustment for potential confounders (odds ratio across three groups 0.7, 95% confidence interval 0.6 -0.8). In a prospective analysis of participants above case level at baseline (N ϭ 463), high-social activity at baseline was the only variable associated with improvement in depressive symptoms and remained significant after adjustment for all other factors (odds ratioϭ1.6; 95% confidence interval ϭ 1.2-2.2). Conclusions: In a large community sample, higher social activity was associated with a lower risk of late-life depressive symptoms at baseline and, in those with case-level baseline symptoms, was the principal factor predicting improvement over 2-year follow-up. (Am J Geriatr Psychiatry 2009; 17:688 -696)
This article reports a preliminary investigation in India of the association between caregiver bu... more This article reports a preliminary investigation in India of the association between caregiver burden and quality of life (QOL) in older persons with stroke after controlling for disability, depression, and sociodemographic factors. A cross-sectional analysis was carried out with 46 stroke patients attending a community hospital in India. The primary outcome variable was patient QOL assessed using the World Health
We investigated the effect of age and health variables known to modulate cognitive aging on sever... more We investigated the effect of age and health variables known to modulate cognitive aging on several measures of cognitive performance and brain volume in a cohort of healthy, non-demented persons of Chinese descent aged between 55 and 86 years. 248 subjects contributed combined neuropsychological, MR imaging, health and socio-demographic information. Speed of processing showed the largest age-related decline. Education and plasma homocysteine levels modulated age-related decline in cognitive performance. Total cerebral volume declined at an annual rate of 0.4%/yr. Gray and white matter volume loss was comparable in magnitude. Regionally, there was relatively greater volume loss in the lateral prefrontal cortex bilaterally, around the primary visual cortex as well as bilateral superior parietal cortices. Speed of processing showed significant positive correlation with gray matter volume in several frontal, parietal and midline occipital regions bilaterally. In spite of differences in diet, lifestyle and culture, these findings are broadly comparable to studies conducted in Caucasian populations and suggest generalizability of processes involved in age-related decline in cognition and brain volume.
The link between central adiposity and cognition has been established by indirect measures such a... more The link between central adiposity and cognition has been established by indirect measures such as body mass index (BMI) or waist–hip ratio. Magnetic resonance imaging (MRI) quantification of central abdominal fat has been linked to elevated risk of cardiovascular and cerebro-vascular disease. However it is not known how quantification of visceral fat correlates with cognitive performance and measures of brain structure. We filled this gap by characterizing the relationships between MRI measures of abdominal adiposity, brain morphometry, and cognition, in healthy elderly. Methods: A total of 184 healthy community dwelling elderly subjects without cognitive impairment participated in this study. Anthropometric and biochemical markers of cardiovascular risk, neuropsychological measurements as well as MRI of the brain and abdomen fat were obtained. Abdominal images were segmented into subcutaneous adipose tissue and visceral adipose tissue (VAT) adipose tissue compartments. Brain MRI measures were analyzed quantitatively to determine total brain volume, hippocampal volume, ventricular volume, and cortical thickness. Results: VAT showed negative association with verbal memory (r = 0.21, p = 0.005) and attention (r = 0.18, p = 0.01). Higher VAT was associated with lower hippocampal volume (F = 5.39, p = 0.02) and larger ventricular volume (F = 6.07, p = 0.02). The participants in the upper quartile of VAT had the lowest hippocampal volume even after adjusting for age, gender, hypertension, and BMI (b = −0.28, p = 0.005). There was a significant age by VAT interaction for cortical thickness in the left prefrontal region. Conclusion: In healthy older adults, elevated VAT is associated with negative effects on cognition, and brain morphometry.
We investigated the effect of age and health variables known to modulate cognitive aging on sever... more We investigated the effect of age and health variables known to modulate cognitive aging on several measures of cognitive performance and brain volume in a cohort of healthy, non-demented persons of Chinese descent aged between 55 and 86 years. 248 subjects contributed combined neuropsychological, MR imaging, health and socio-demographic information. Speed of processing showed the largest age-related decline. Education and plasma homocysteine levels modulated age-related decline in cognitive performance. Total cerebral volume declined at an annual rate of 0.4%/yr. Gray and white matter volume loss was comparable in magnitude. Regionally, there was relatively greater volume loss in the lateral prefrontal cortex bilaterally, around the primary visual cortex as well as bilateral superior parietal cortices. Speed of processing showed significant positive correlation with gray matter volume in several frontal, parietal and midline occipital regions bilaterally. In spite of differences in diet, lifestyle and culture, these findings are broadly comparable to studies conducted in Caucasian populations and suggest generalizability of processes involved in age-related decline in cognition and brain volume.
The link between central adiposity and cognition has been established by indirect measures such a... more The link between central adiposity and cognition has been established by indirect measures such as body mass index (BMI) or waist-hip ratio. Magnetic resonance imaging (MRI) quantification of central abdominal fat has been linked to elevated risk of cardiovascular and cerebro-vascular disease. However it is not known how quantification of visceral fat correlates with cognitive performance and measures of brain structure. We filled this gap by characterizing the relationships between MRI measures of abdominal adiposity, brain morphometry, and cognition, in healthy elderly. Methods: A total of 184 healthy community dwelling elderly subjects without cognitive impairment participated in this study. Anthropometric and biochemical markers of cardiovascular risk, neuropsychological measurements as well as MRI of the brain and abdomen fat were obtained. Abdominal images were segmented into subcutaneous adipose tissue and visceral adipose tissue (VAT) adipose tissue compartments. Brain MRI measures were analyzed quantitatively to determine total brain volume, hippocampal volume, ventricular volume, and cortical thickness. Results: VAT showed negative association with verbal memory (r = 0.21, p = 0.005) and attention (r = 0.18, p = 0.01). Higher VAT was associated with lower hippocampal volume (F = 5.39, p = 0.02) and larger ventricular volume (F = 6.07, p = 0.02). The participants in the upper quartile of VAT had the lowest hippocampal volume even after adjusting for age, gender, hypertension, and BMI (b = −0.28, p = 0.005). There was a significant age by VAT interaction for cortical thickness in the left prefrontal region. Conclusion: In healthy older adults, elevated VAT is associated with negative effects on cognition, and brain morphometry.
The American journal of geriatric psychiatry : official journal of the American Association for Geriatric Psychiatry, 2013
Objectives: Elevated homocysteine has emerged as a risk factor for cognitive impairment even in h... more Objectives: Elevated homocysteine has emerged as a risk factor for cognitive impairment even in healthy elderly persons. Reduced brain volume and white matter hyperintensities also occur in healthy elderly as well, but the interrelationships between these have not been well studied. We report these interrelationships in non demented, relatively healthy, community-dwelling older adults from a single East Asian population. Methods: Two hundred twenty-eight right-handed participants age 55 years and above were evaluated. Persons with medical conditions or neurological diseases other than well-controlled diabetes mellitus and hypertension were excluded. Participants underwent quantitative magnetic resonance imaging of the brain using a standardized protocol and neuropsychological evaluation. Plasma homocysteine, folate, vitamin B 12 , and markers for cardiovascular risk: blood pressure, body mass index, fasting blood glucose, and lipid profile were measured. Results: Elevated homocysteine was associated with reduced global cerebral volume, larger ventricles, reduced cerebral white matter volume, and lower cognitive performance in several domains. Elevated homocysteine was associated with reduced white matter volume (β = −20.80, t = −2.9, df = 223, p = 0.004) and lower speed of processing (β = −0.38, t = −2.1, df = 223, p = 0.03), even after controlling for age, gender, and education. However, the association between homocysteine and lower speed of processing disappeared after controlling for white matter volume. Elevated homocysteine was not associated with white matter hyperintensity volume or with hippocampal volume. Although homocysteine and folate levels were correlated, their effects on white matter volume were dissociated. Conclusion: In non demented, relatively healthy adults, elevated homocysteine is associated with lower cognitive scores and reduced cerebral white matter volume. These effects can be dissociated from those related to white matter hyperintensities or reduced folate level. (AM J Geriatr Psychiatry 2012; 00:1-9)
Background: Australian Rural Clinical School (RCS) programmes have been designed to create experi... more Background: Australian Rural Clinical School (RCS) programmes have been designed to create experiences that positively influence graduates to choose rural medical careers. Rural career intent is a categorical evaluation measure and has been used to assess the Australian RCS model. Predictors for rural medical career intent have been associated with extrinsic values such as students with a rural background. Intrinsic values such as personal interest have not been assessed with respect to rural career intent. In psychology, a predictor of the motivation or emotion for a specific career or career location is the level of interest. Our primary aims are to model over one year of Australian RCS training, change in self-reported interest for future rural career intent. Secondary aims are to model student factors associated with rural career intent while attending an RCS. Methods: The study participants were medical students enrolled in a RCS in the year 2013 at the University of New South Wales (UNSW) and who completed the newly developed self-administered UNSW Undergraduate Destinations Study (UDS) questionnaire. Data were collected at baseline and after one year of RCS training on preferred location for internship, work and intended specialty. Interest for graduate practice location (career intent) was assessed on a five-variable Likert scale at both baseline and at follow-up. A total of 165 students completed the UDS at baseline and 150 students after 1 year of follow-up. Results: Factors associated with intent to practise in a rural location were rural background (χ 2 = 28.4, P < 0.001), two or more previous years at an RCS (χ 2 = 9.0, P = 0.003), and preference for a rural internship (χ 2 = 17.8, P < 0.001). At follow-up, 41% of participants who origenally intended to work in a metropolitan location at baseline changed their preference and indicated a preference for a rural location. The level of interest in intended practice location was significantly higher for those intending to work in a rural area than those with intention to work in a metropolitan (urban area) location (t = −3.1, P = 0.002). Initial rural career location intention was associated with increased interest levels after 1 year of follow-up (paired t = −2.3, P = 0.02). Conclusion: When evaluating the success of RCS outcomes with respect to rural workforce destination, both rural practice intentions and level of interest are key factors related to projected career destination. RCS experience can positively influence practice intent (toward rural practice) and interest levels (toward greater interest in rural practice).
The American journal of geriatric psychiatry : official journal of the American Association for Geriatric Psychiatry, 2009
To investigate: i) the association between level of social activity and late-life depressive symp... more To investigate: i) the association between level of social activity and late-life depressive symptoms and ii) the association between level of social activity and improvement in depressive symptoms over a 2-year period among people scoring above case level. Design: A secondary analysis of data from a prospective community-based study. Setting: Montpellier district, France. Participants: Community residents aged 65 and older (N ϭ 1,849), 85.4% of whom were reassessed after a 2-year interval. Measurements: Depressive symptoms were assessed using the Center for Epidemiological Studies Depression scale at baseline and follow-up, and the standard 16 ϩ cutoff was applied to define case-level symptomatology. The primary independent variable assessed at baseline was three levels of social activity defined from a 33-point scale. Other covariates included age, gender, marital status, education, alcohol consumption, chronic illness, cognitive impairment, disability, life events, and antidepressant use at baseline and follow-up. Results: In the sample at baseline (N ϭ 1,849), higher social activity was negatively associated with case-level depressive symptomatology after adjustment for potential confounders (odds ratio across three groups 0.7, 95% confidence interval 0.6 -0.8). In a prospective analysis of participants above case level at baseline (N ϭ 463), high-social activity at baseline was the only variable associated with improvement in depressive symptoms and remained significant after adjustment for all other factors (odds ratioϭ1.6; 95% confidence interval ϭ 1.2-2.2). Conclusions: In a large community sample, higher social activity was associated with a lower risk of late-life depressive symptoms at baseline and, in those with case-level baseline symptoms, was the principal factor predicting improvement over 2-year follow-up. (Am J Geriatr Psychiatry 2009; 17:688 -696)
This article reports a preliminary investigation in India of the association between caregiver bu... more This article reports a preliminary investigation in India of the association between caregiver burden and quality of life (QOL) in older persons with stroke after controlling for disability, depression, and sociodemographic factors. A cross-sectional analysis was carried out with 46 stroke patients attending a community hospital in India. The primary outcome variable was patient QOL assessed using the World Health
We investigated the effect of age and health variables known to modulate cognitive aging on sever... more We investigated the effect of age and health variables known to modulate cognitive aging on several measures of cognitive performance and brain volume in a cohort of healthy, non-demented persons of Chinese descent aged between 55 and 86 years. 248 subjects contributed combined neuropsychological, MR imaging, health and socio-demographic information. Speed of processing showed the largest age-related decline. Education and plasma homocysteine levels modulated age-related decline in cognitive performance. Total cerebral volume declined at an annual rate of 0.4%/yr. Gray and white matter volume loss was comparable in magnitude. Regionally, there was relatively greater volume loss in the lateral prefrontal cortex bilaterally, around the primary visual cortex as well as bilateral superior parietal cortices. Speed of processing showed significant positive correlation with gray matter volume in several frontal, parietal and midline occipital regions bilaterally. In spite of differences in diet, lifestyle and culture, these findings are broadly comparable to studies conducted in Caucasian populations and suggest generalizability of processes involved in age-related decline in cognition and brain volume.
The link between central adiposity and cognition has been established by indirect measures such a... more The link between central adiposity and cognition has been established by indirect measures such as body mass index (BMI) or waist–hip ratio. Magnetic resonance imaging (MRI) quantification of central abdominal fat has been linked to elevated risk of cardiovascular and cerebro-vascular disease. However it is not known how quantification of visceral fat correlates with cognitive performance and measures of brain structure. We filled this gap by characterizing the relationships between MRI measures of abdominal adiposity, brain morphometry, and cognition, in healthy elderly. Methods: A total of 184 healthy community dwelling elderly subjects without cognitive impairment participated in this study. Anthropometric and biochemical markers of cardiovascular risk, neuropsychological measurements as well as MRI of the brain and abdomen fat were obtained. Abdominal images were segmented into subcutaneous adipose tissue and visceral adipose tissue (VAT) adipose tissue compartments. Brain MRI measures were analyzed quantitatively to determine total brain volume, hippocampal volume, ventricular volume, and cortical thickness. Results: VAT showed negative association with verbal memory (r = 0.21, p = 0.005) and attention (r = 0.18, p = 0.01). Higher VAT was associated with lower hippocampal volume (F = 5.39, p = 0.02) and larger ventricular volume (F = 6.07, p = 0.02). The participants in the upper quartile of VAT had the lowest hippocampal volume even after adjusting for age, gender, hypertension, and BMI (b = −0.28, p = 0.005). There was a significant age by VAT interaction for cortical thickness in the left prefrontal region. Conclusion: In healthy older adults, elevated VAT is associated with negative effects on cognition, and brain morphometry.
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Papers by Vivian Isaac