Biomedical subjects

John T O'Brien

Publications and source records attributed to John T O'Brien.

59 records · Page 4Linked to original sources

PubMed2002

Cognitive associations of subcortical white matter lesions in older people.

Hyperintense lesions (HL), as visualized on T2-weighted or FLAIR MRI, are a common finding in older people, but their clinical significance and influence on cognitive function remain to be clarified. We investigated the relationship between HL in deep white and gray matter structures and cognition in older subjects. We recruited 154 nondemented (Mini-Mental State Examination > 24) subjects (79 males) over the age of 70 from primary care (103 subjects with mild hypertension and 51 normotensive subjects). All subjects underwent FLAIR and proton density and T2-weighted axial 1.5-tesla MRI scans (slice thickness: 5 mm). The scans were rated for the presence and distribution of HL in the subcortical gray matter (caudate, putamen, globus pallidus, thalamus) and associated white matter tracts (internal/external capsule). Subjects (n = 149) underwent a comprehensive cognitive assessment involving tests of attention, processing speed, episodic memory, working memory, and executive function. Partial correlations (correcting for age, systolic blood pressure, and New Adult Reading Test [NART] score) were performed to investigate the relationship between cognition and white matter change. HL were found in 49% of subjects. HL in both the gray (thalamus and caudate) and white matter were significantly associated with impaired cognitive function in tasks involving processing speed and/or executive function, but showed no associations with episodic or working memory. HL in both subcortical gray matter structures and associated fiber tracts correlate with impairments in attention, executive function and processing, and memory retrieval speed in nondemented older community-dwelling subjects. Such lesions may be an important cause of age-related attentional and executive dysfunction in the elderly, as well as temporal lobe and hippocampal changes that have previously been reported to be associated with impairments to the ability to actually store and retrieve information from memory.

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PubMed2002

Effects of rapid tryptophan depletion on salivary and plasma cortisol in Alzheimer's disease and the healthy elderly.

Serotonergic function is reduced in dementia of Alzheimer type (DAT) and abnormalities in the hypothalamic-pituitary-adrenal (HPA) axis are also common. There is considerable interaction between the two systems. Effects of lowering brain serotonin on salivary and plasma cortisol were assessed in patients with DAT and in control subjects. A double-blind, cross-over design involving administration of two nutritionally balanced amino acid mixtures with or without tryptophan was used. Salivary and plasma cortisol were measured at intervals before and after the drink. DAT patients had higher salivary cortisol than controls. Despite a reduction of approximately 70% in plasma free tryptophan after 4 h in both groups, there was no effect on salivary or plasma cortisol. We conclude that, in subjects with DAT and healthy elderly subjects, acute tryptophan depletion had no effect on cortisol secretion.

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PubMed2002

Effects of hydrocortisone administration on cognitive function in the elderly.

Previous studies have found adverse effects of both acute and chronic elevations of corticosteroids on cognitive function in humans and that cortisol levels may predict cognitive decline in elderly subjects. However, no previous studies have directly investigated the effects of hydrocortisone on cognitive functioning in the healthy elderly. Sixteen healthy elderly subjects took part in a placebo-controlled, double-blind, cross-over trial. Hydrocortisone 20 mg or placebo was administered twice, 12 h and 1 h before cognitive testing. On each occasion, a battery of neuropsychological tests was performed which included tests of attention, working memory, declarative memory and executive function. Salivary cortisol levels at the time of testing were elevated approximately 10-fold following hydrocortisone compared with placebo. No significant effects were found on memory or a range of other cognitive functions. The lack of effect of this regime of hydrocortisone is in contrast to studies in younger subjects. The elderly may be less sensitive to cognitive effects of short-term increases in cortisol levels, possibly due to an age-related downregulation of hippocampal glucocorticoid receptors.

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PubMed2002

Aromatherapy as a safe and effective treatment for the management of agitation in severe dementia: the results of a double-blind, placebo-controlled trial with Melissa.

BACKGROUND: Behavioral and psychological symptoms in dementia are frequent and are a major management problem, especially for patients with severe cognitive impairment. Preliminary reports have indicated positive effects of aromatherapy using select essential oils, but there are no adequately powered placebo-controlled trials. We conducted a placebo-controlled trial to determine the value of aromatherapy with essential oil of Melissa officinalis (lemon balm) for agitation in people with severe dementia. METHOD: Seventy-two people residing in National Health Service (U.K.) care facilities who had clinically significant agitation in the context of severe dementia were randomly assigned to aromatherapy with Melissa essential oil (N = 36) or placebo (sunflower oil) (N = 36). The active treatment or placebo oil was combined with a base lotion and applied to patients' faces and arms twice a day by caregiving staff. Changes in clinically significant agitation (Cohen-Mansfield Agitation Inventory [CMAI]) and quality of life indices (percentage of time spent socially withdrawn and percentage of time engaged in constructive activities, measured with Dementia Care Mapping) were compared between the 2 groups over a 4-week period of treatment. RESULTS: Seventy-one patients completed the trial. No significant side effects were observed. Sixty percent (21/35) of the active treatment group and 14% (5/36) of the placebo-treated group experienced a 30% reduction of CMAI score, with an overall improvement in agitation (mean reduction in CMAI score) of 35% in patients receiving Melissa balm essential oil and 11% in those treated with placebo (Mann-Whitney U test; Z = 4.1, p < .0001). Quality of life indices also improved significantly more in people receiving essential balm oil (Mann-Whitney U test; percentage of time spent socially withdrawn: Z = 2.6, p = .005; percentage of time engaged in constructive activities: Z = 3.5, p = .001). CONCLUSION: The finding that aromatherapy with essential balm oil is a safe and effective treatment for clinically significant agitation in people with severe dementia, with additional benefits for key quality of life parameters, indicates the need for further controlled trials.

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PubMedDate not supplied

A volumetric study of MRI signal hyperintensities in late-life depression.

OBJECTIVE: An increase in white-matter lesions has been previously described in older subjects with depression. The authors investigated whether the regional location varied between depressed and normal subjects and determined the relationship of magnetic resonance (MR) signal hyperintensities to known clinical risk factors for vascular disease. METHODS: Authors used automated image-processing software to determine volumes of signal hyperintensities from MR brain scans of older people with depression (N=29; mean age: 76 years) and normal subjects of similar age (N=32). RESULTS: Overall, subjects with depression had a significantly greater frontal-lobe white-matter lesion volume than normal subjects (0.35% versus 0.22%). However, after excluding subjects with hypertension, diabetes, or ischemic heart disease (leaving 14 depressed and 15 normal subjects), we found even greater differences between groups, with a larger volume of MR signal hyperintensities in the frontal region of the depressed group, but no difference in the basal ganglia or parietal and occipital lobes. CONCLUSION: The results support the "vascular depression" hypothesis and suggest that those with depression but without traditional vascular risk factors may be much more susceptible to cerebrovascular disease than normal subjects. The mechanisms for this increased susceptibility remain to be determined.

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