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Biomedical subjects

John Grimley Evans

Publications and source records attributed to John Grimley Evans.

At least 19 recordsLinked to original sources
PubMed2006

Clinical relevance of low serum vitamin B12 concentrations in older people: the Banbury B12 study.

BACKGROUND: low vitamin B12 concentrations are common in older people, but the clinical relevance of biochemical evidence of vitamin B12 deficiency in the absence of anaemia is uncertain. OBJECTIVE: to examine associations of cognitive impairment, depression and neuropathy with blood measurements of vitamin B12 and folate status in older people. DESIGN: cross-sectional study in general practice in Banbury, England. PARTICIPANTS: a total of 1,000 individuals aged 75 years or older living in the community. RESULTS: low vitamin B12 concentrations were identified in 13% of older people and were associated with memory impairment and depression. After adjustment for age, sex and smoking, individuals with vitamin B12 or holotranscobalamin (holoTC) in the bottom compared with top quartiles had a 2-fold risk (OR = 2.17; 95% CI 1.11-4.27) and a 3-fold risk (OR = 3.02; 95% CI 1.31-6.98) of cognitive impairment, respectively. Low vitamin B12 status was also associated with missing ankle tendon jerks but not with depression. Treatment with vitamin B12 for 3 months corrected the biochemical abnormalities but had no effect on any of the clinical measurements. CONCLUSIONS: low vitamin B12 concentrations are associated with cognitive impairment and missing ankle tendon jerks in older people in the absence of anaemia. Large-scale trials of vitamin B12 supplementation are required to assess the clinical significance of these associations.

Aged↗
PubMed2006

Interactions among polymorphisms in folate-metabolizing genes and serum total homocysteine concentrations in a healthy elderly population.

BACKGROUND: Homocysteine concentrations are influenced by vitamin status and genetics, especially several polymorphisms in folate-metabolizing genes. OBJECTIVE: We examined the interactions and associations with serum total homocysteine (tHcy) and folate concentrations of polymorphisms in the following folate-metabolizing genes: methylenetetrahydrofolate reductase (MTHFR), reduced folate carrier 1 (RFC1), and glutamate carboxypeptidase II (GCPII). DESIGN: Healthy volunteers (436 men and 606 women; mean age: 77.9 y) were randomly selected from among residents of Oxford, United Kingdom. We determined the individual effects and interactions of the MTHFR 677C-->T, MTHFR 1298A-->C, RFC1 80G-->A, and GCPII 1561C-->T polymorphisms on serum tHcy and folate concentrations. RESULTS: Subjects with the MTHFR 677TT genotype had higher serum tHcy concentrations than did those with the MTHFR 677CC genotype (P < 0.001), and this effect was greater in subjects with low serum folate status (P for interaction = 0.026). The MTHFR 1298A-->C, RFC1 80G-->A, and GCPII 1561C-->T polymorphisms had no individual effects on serum tHcy or folate concentrations. There was no interactive effect of the MTHFR 677C-->T and MTHFR 1298A-->C polymorphisms on tHcy concentrations. An interaction (P = 0.05) was observed between the MTHFR 677TT and RFC1 80GG genotypes, whereby persons with this genotype combination had a mean (+/-SEM) serum tHcy concentration (18.5 +/- 1.2 micromol/L) that was 5.1 micromol/L greater than the mean value of 13.4 +/- 0.2 micromol/L for the whole population. CONCLUSIONS: Folate and tHcy concentrations were not affected individually by the MTHFR 1298A-->C, RFC1 80G-->A, or GCPII 1561C-->T polymorphisms or by combinations of the MTHFR 677C-->T and MTHFR 1298A-->C genotypes. An interaction between the MTHFR 677TT and RFC1 80GG genotypes was observed whereby persons with this combination had higher serum tHcy.

Aged↗
PubMed2005

Candidate gene association study of solute carrier family 11a members 1 (SLC11A1) and 2 (SLC11A2) genes in Alzheimer's disease.

Divalent cations are strongly implicated in Alzheimer's disease (AD) pathogenesis, and can regulate amyloid beta-peptide aggregation. The proton-divalent cation transporters encoded by SLC11A1 (formerly NRAMP1) on chromosome 2q35, and SLC11A2 (also known as DCT1 and DMT1) on chromosome 12q13, are expressed in the brain and regulate ion homeostasis from endosomal compartments. SLC11A1 also has pleiotropic effects on pro-inflammatory responses that may be important in AD. We analyzed seven informative polymorphisms in the SLC11A1 and SLC11A2 genes encoding these divalent cation transporters in a sample of 216 late-onset AD cases and 323 age-matched controls. We found only borderline evidence (p=0.08) for an allelic association between SNP rs407135 at SLC11A2 and AD, in which the variant allele was protective (odd ratio (OR) 0.77; 95% CI 0.56-1.04) relative to the more common allele. There was no interaction with apolipoprotein E (APOE) varepsilon4, but stratification by gender showed that all of the effect of SLC11A2 was in the male patient group. No other associations with AD were observed at SLC11A1 or SLC11A2, indicating no major effect of either gene for the occurrence of AD.

Age of Onset↗
PubMed2005

Candidate gene association studies of genes involved in neuronal cholinergic transmission in Alzheimer's disease suggests choline acetyltransferase as a candidate deserving further study.

Consistent deficits in the cholinergic system are evident in the brains of Alzheimer's Disease (AD) patients, including reductions in the activities of acetylcholine, acetylcholinesterase (AChE), and choline acetyltransferase (ChAT), increased butyrylcholinesterase (BChE) activity, and a selective loss of nicotinic acetylcholine receptors (nAChRs). Accordingly, we have analyzed polymorphisms in the genes encoding AChE, ChAT, BChE, and several of the subunit genes from neuronal nAChRs, for genetic associations with late-onset AD. A significant association for disease was detected for a non-coding polymorphism in ChAT (allele chi(1) (2) = 12.84, P = 0.0003; genotype chi(2) (2) = 11.89, P = 0.0026). Although replication analysis did not confirm the significance of this finding when the replication samples were considered alone (allele chi(1) (2) = 1.02, P = 0.32; genotype chi(2) (2) = 1.101, P = 0.58) the trends were in the correct direction and a significant association remained when the two sample sets were pooled (allele chi(1) (2) = 12.37, P = 0.0004; genotype chi(2) (2) = 11.61, P = 0.003). Previous studies have reported significant disease associations for both the K-variant of BChE and the coding ChAT rs3810950 polymorphism with AD. Replication analyses of these two loci failed to detect any significant association for disease in our case-control samples.

Aged↗
PubMed2004

Evidence-based pharmacotherapy of Alzheimer's disease.

Dementia is an acquired global impairment of cognitive capacities. Approximately 5% of people aged over 65 yr are affected by dementia, and some 70% of cases are thought to be due primarily to Alzheimer's disease. Descriptions of the clinical manifestations of Alzheimer's disease have been increasingly refined in the last decade but there is no diagnostic test for what remains fundamentally a pathologically defined condition. At the present time interventions for Alzheimer's disease are limited to those that modify the manifestations of the disease, and foremost amongst the candidates available are the cholinesterase inhibitors. The rationale for the use of cholinergic drugs for Alzheimer's disease lies in enhancing the secretion of, or prolonging the half-life of, acetylcholine in the brain. Several potential compounds have been tested, but short half-lives and a high incidence of cholinergic and other adverse effects have eliminated most. Only three are widely licensed for use, donepezil, galantamine and rivastigmine. Their efficacy is relatively modest. These drugs have been tested in 32 randomized, placebo-controlled trials. The trials assess cognitive function primarily, and in addition they may assess global function, activities of daily living, quality of life and behavioural disturbance typically over 3 or 6 months. The performance of each drug is summarized in a Cochrane review, a systematic review carried out according to strict guidelines. There was a significant benefit in favour of treatment compared with placebo for cognition and activities of daily living, but withdrawals due to adverse events were significantly higher for treatment than placebo for all three drugs. There is little evidence from direct comparisons between the three drugs. There are several economic analyses of the cost-effectiveness of these drugs, but the findings cannot be considered robust owing to inadequate data. A range of other pharmacological treatments have been tested, including selegiline, piracetam, vitamin E, Ginkgo biloba, anti-inflammatory drugs and hormone replacement therapy, but, so far, Cochrane reviews have not established the efficacy of these interventions for Alzheimer's disease. A Cochrane review of memantine shows benefits on cognitive and global function of the same order of magnitude as seen for the cholinesterase inhibitors. Memantine has been licensed in Europe for treatment of patients with moderately severe to severe Alzheimer's disease.

Aged↗
PubMed2004

Candidate gene association studies of the alpha 4 (CHRNA4) and beta 2 (CHRNB2) neuronal nicotinic acetylcholine receptor subunit genes in Alzheimer's disease.

Consistent deficits in the cholinergic system are evident in Alzheimer's disease (AD) patients, including selective loss of alpha4beta2 nicotinic acetylcholine receptors in the brains of AD patients. Knockout mice for the beta2 subunit have impaired neuronal survival in ageing. Accordingly, we have analysed polymorphisms in the genes that encode the alpha4 and beta2 subunits, CHRNA4 and CHRNB2 respectively, for genetic associations with late-onset AD. A significant association for disease was observed for a non-coding polymorphism in CHRNB2 (odds ratio=0.57, 95% confidence interval=0.35-0.95, P=0.024). Replication analysis was performed in two further sample sets. While these did not individually yield significant results, a significant association remained when all samples were pooled (odds ratio=0.70, 95% confidence interval=0.52-0.95, P=0.019). These data suggest that this variant warrants further examination in large case-control series.

Aged↗
PubMed2004

Donepezil for the symptomatic treatment of patients with mild to moderate Alzheimer's disease: a meta-analysis of individual patient data from randomised controlled trials.

BACKGROUND: The objective was to evaluate the efficacy and tolerability of donepezil (5 and 10 mg/day) compared with placebo in alleviating manifestations of mild to moderate Alzheimer's disease (AD). METHOD: A systematic review of individual patient data from Phase II and III double-blind, randomised, placebo-controlled studies of up to 24 weeks and completed by 20 December 1999. The main outcome measures were the ADAS-cog, the CIBIC-plus, and reports of adverse events. RESULTS: A total of 2376 patients from ten trials were randomised to either donepezil 5 mg/day (n = 821), 10 mg/day (n = 662) or placebo (n = 893). Cognitive performance was better in patients receiving donepezil than in patients receiving placebo. At 12 weeks the differences in ADAS-cog scores were 5 mg/day-placebo: - 2.1 [95% confidence interval (CI), - 2.6 to - 1.6; p < 0.001], 10 mg/day-placebo: - 2.5 ( - 3.1 to - 2.0; p < 0.001). The corresponding results at 24 weeks were - 2.0 ( - 2.7 to - 1.3; p < 0.001) and - 3.1 ( - 3.9 to - 2.4; p < 0.001). The difference between the 5 and 10 mg/day doses was significant at 24 weeks (p = 0.005). The odds ratios (OR) of improvement on the CIBIC-plus at 12 weeks were: 5 mg/day-placebo 1.8 (1.5 to 2.1; p < 0.001), 10 mg/day-placebo 1.9 (1.5 to 2.4; p < 0.001). The corresponding values at 24 weeks were 1.9 (1.5 to 2.4; p = 0.001) and 2.1 (1.6 to 2.8; p < 0.001). Donepezil was well tolerated; adverse events were cholinergic in nature and generally of mild severity and brief in duration. CONCLUSION: Donepezil (5 and 10 mg/day) provides meaningful benefits in alleviating deficits in cognitive and clinician-rated global function in AD patients relative to placebo. Increased improvements in cognition were indicated for the higher dose.

Adult↗
PubMed2003

Screening for vitamin B-12 and folate deficiency in older persons.

BACKGROUND: Vitamin B-12 deficiency is usually accompanied by elevated concentrations of serum total homocysteine (tHcy) and methylmalonic acid (MMA). Folate deficiency also results in elevated tHcy. Measurement of these metabolites can be used to screen for functional vitamin B-12 or folate deficiency. OBJECTIVE: We assessed the prevalence of vitamin B-12 and folate deficiency in a population-based study (n = 1562) of older persons living in Oxford City, United Kingdom. DESIGN: We postulated that, as vitamin B-12 or folate concentrations declined from adequate to impaired levels, tHcy (or MMA) concentrations would increase. Individuals were classified as being at high risk of vitamin B-12 deficiency if they had low vitamin B-12 (< 150 pmol/L) or borderline vitamin B-12 (150-200 pmol/L) accompanied by elevated MMA (> 0.35 micromol/L) or tHcy (> 15.0 micromol/L). Individuals were classified as being at high risk of folate deficiency if they had low folate (< 5 nmol/L) or borderline folate (5-7 nmol/L) accompanied by elevated tHcy (> 15 micromol/L). RESULTS: Cutoffs of 15.0 micro mol/L for tHcy and 0.35 micro mol/L for MMA identified persons with normal or elevated concentrations. Among persons aged 65-74 and >or= 75 y, respectively, approximately 10% and 20% were at high risk of vitamin B-12 deficiency. About 10% and 20%, respectively, were also at high risk of folate deficiency. About 10% of persons with vitamin B-12 deficiency also had folate deficiency. CONCLUSION: Use of tHcy or MMA among older persons with borderline vitamin concentrations may identify those at high risk of vitamin B-12 deficiency who should be considered for treatment.

Age Factors↗
PubMed2002

Neuromuscular stimulation of the quadriceps muscle after hip fracture: a randomized controlled trial.

OBJECTIVE: To study the feasibility and effect of neuromuscular stimulation on recovery of mobility after surgical fixation for hip fracture. DESIGN: Double-blind study with stratified randomization. SETTING: Home-based rehabilitation program. PARTICIPANTS: Twenty-four women over the age of 75 years with hip fracture. INTERVENTIONS: Neuromuscular or placebo stimulation of the quadriceps muscle of the fractured leg, applied for 3 hours a day, for 6 weeks, commencing 1 week after surgery. MAIN OUTCOME MEASURES: Recovery of walking speed and ability, postural stability, lower-limb muscle power, and pain at 7 and 13 weeks after surgery. RESULTS: Women in the neuromuscular stimulation group showed faster recovery of mobility. Of the women receiving stimulation, 9 of 12 recovered their prior levels of indoor mobility ability by 13 weeks compared with 3 of 12 in the placebo group (Fisher exact test, P=.046). There were no differences in recovery of walking speed in the first 7 weeks, but women in the stimulation group had greater recovery between 7 and 13 weeks (mean difference=-.13m/s; 95% confidence interval, -.23 to -.01). CONCLUSIONS: Neuromuscular stimulation at home is feasible and may be effective in speeding recovery of mobility after surgical fixation of hip fracture.

Aged↗
PubMed2002

An N-of-1 randomized controlled trial ('N-of-1 trial') of donepezil in the treatment of non-progressive amnestic syndrome.

INTRODUCTION: a professional man sustained a residual, persisting, isolated impairment of short-term memory secondary to severe carbon monoxide poisoning. Informal, open trial of the cholinesterase inhibitor donepezil resulted in uncertain benefit. PROTOCOL: an N-of-1 randomized, double-blind controlled trial of donepezil against placebo. Placebo-induced headache permitted evaluation of donepezil at only the 5 mg dose. RESULTS: there was no improvement in short-term memory. CONCLUSION: the trial excluded significant benefit of donepezil 5 mg in this patient, preventing long-term unnecessary prescription. Beneficial effects in other similar patients or at higher dosage cannot be excluded.

Cholinesterase Inhibitors↗