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Biomedical subjects

C H Bamford

Publications and source records attributed to C H Bamford.

11 recordsLinked to original sources
PubMed1999

Costs of formal care for frail older people in England: the resource implications study of the MRC cognitive function and ageing study (RIS MRC CFAS).

The aim of this paper is to quantify service use and costs of supporting frail older people at home in the community, using data collected in a longitudinal multicentre stratified randomised study for 1055 mentally frail, physically frail, and mentally and physically frail subjects. Average costs per person per week were found to total 64.45 Pounds Sterling, with a small number of services accounting for a large proportion of the total costs. The level of services offered by the nonstatutory voluntary and private sectors was found to be small. To highlight issues for policy makers, the extent of cost variations between a number of different subgroups were calculated. These bivariate analyses revealed substantial variation in costs, especially according to household structure, type of frailty, whether admission to continuing care accommodation occurred and survival. Multiple regression analysis demonstrated that 26% of the variation in log average weekly costs could be explained by a number of socio-demographic and health status variables. A particularly close relationship was observed between costs and whether admission to continuing care accommodation occurred, highlighting a need for policy-makers to examine the nature and scale of provision of alternative community based care packages. The results demonstrate that descriptive cost data such as those presented can provide information useful to the planning process, enabling more informed choices to be made over the provision of services for particular groups of people.

Aged↗
PubMed1998

Estimation of a multiproduct cost function for physically frail older people.

Using the theory of multiproduct cost functions, this paper derives a cost function for physically frail older people living in private households, based on data collected between 1991 and 1995, for 472 subjects aged 65 years of age or over in four areas of England. The main characteristic of the cost function is that output categories are classified in terms of movements between different health states. These were measured by changes in activities of daily living (ADL) over 2 years, with 'low' ADL representing better functional ability than 'high' ADL. Empirical application of the approach, using four states defined in terms of worsening progression (stable low ADL; deteriorated or improved ADL; stable high ADL; deceased), indicated more favourable states were associated with lower costs. Multivariate analysis showed that the derived states were significantly related to costs which, when combined with variables indicating presence of particular chronic health conditions (diabetes or previous stroke), admission to continuing care accommodation and household structure, explained one-fifth of the variation in log average costs per week. Variables such as age, sex, carer input, social networks and level of cognitive functioning had no independent impact on costs. These findings could be used as a starting point for those interested in predicting the cost implications associated with the ageing population.

Activities of Daily Living↗
PubMed1997

Psychological distress among informal supporters of frail older people at home and in institutions. The Resource Implications Study Group of the MRC Cognitive Function and Ageing Study.

OBJECTIVE: Investigate presence of psychiatric morbidity in informal carers using 30-item General Health Questionnaire (GHQ) and examine which factors best predict psychiatric morbidity. DESIGN: Two-year longitudinal, panel survey of informal supporters of frail elderly subjects, using semi-structured interview schedules. Subjects were those defined as frail after screening stratified random sample of people aged 65 or over. SETTING: Informal supporters of frail elderly subjects residing in private households or residential or nursing homes in four UK districts. RESPONDENTS: 623 informal supporters of subjects living at home, 129 regular visitors of those in long-term care. MEASURE: 30-item GHQ (cross-sectional analysis). RESULTS: Stepwise multiple regression indicated main predictors of high GHQ scores in key supporters were: subjects had at least three problems of behaviour (b = 1.56, 95% CI 1.25-1.94); supporters had to alter working hours (b = 1.70, 95% CI 1.15-2.51); supporters were female (b =1.26, 95% CI 1.06-1.50). The following variables predicted low GHQ scores: supporters able to leave subject all day (b = 0.71, 95% CI 0.64-0.80); subjects never wandered (b = 0.78, 95% CI 0.62-0.99); supporters were 'other relatives' or friends of subject (b = 0.74, 95% CI 0.59-0.91). For visitors, spouses were most likely to have high GHQ scores (b = 2.46, 95% CI 1.32-4.57). CONCLUSIONS: Results suggest the need for greater collaboration between formal and informal care. Little work has been carried out to ascertain which interventions are most effective in alleviating carer stress: a series of randomized controlled trials to determine long-term effectiveness of various interventions for different groups of carers is required.

Adult↗
PubMed1992

Chemical methods for improving the haemocompatibility of synthetic polymers.

Synthetic high polymers differ widely in their interactions with blood, and unfortunately polymers offering promising combinations of mechanical properties for prosthetic applications are rarely those with the highest haemocompatibility. This paper is concerned with methods available for reducing the thrombogenicity of polymer surfaces but does not include discussion of other important issues such as complement activation. A brief review of the processes occurring in blood coagulation is followed by a statement of the chief methods for improving haemocompatibility: (1) coupling anti-platelet agents (e.g. prostaglandins or analogues) or anti-coagulants such as heparin to the surface: (2) 'passivation', for example by increasing the hydrophilicity of the surface: (3) coupling an inert biomaterial (e.g. albumin) or biomimetic (e.g. phosphatidyl choline) to the surface. Chemical techniques for effecting these processes are described, together with some results obtained. An account is also included of solution studies, carried out for mechanistic purposes, of bioactivities of appropriate polymer-drug adducts.

Animals↗
PubMed1991

Influence of molecular structure on the synergistic action of theophylline or dipyridamole derivatives in the prostaglandin-type inhibition of platelet aggregation.

Approximately 30 new derivatives of theophylline and dipyridamole have been prepared and examined as potentiators of the inhibition of platelet aggregation induced by the prostaglandin analogue BW 245C. Potentiating activity has been found to be sensitive to molecular size and also to the presence of specific groups. Polymeric adducts based on dextran, poly(ethylene glycol) or poly(N-vinyl pyrrolidone), and aliphatic esters with alkyl chain-lengths greater than 7 are inactive in potentiation. Derivatives containing carboxyl groups are also inactive. Potentiation is discussed in terms of platelet membrane penetration and extra- and intra-cellular processes. The latter are invoked to account for the enhanced potentiation shown by dipyridamole and derivatives when aggregation is induced by PAF-acether rather than ADP. One derivative of particular interest is the adduct of theophylline with 1,2,5,6-diisopropylidene-D-glucose, containing a furanose ring. This is a more active potentiator than theophylline itself, possibly owing to its molecular resemblance to cAMP. On conversion to the pyranose form all activity is removed.

Animals↗
PubMed1987

Polymeric inhibitors of platelet aggregation. II. Copolymers of dipyridamole and related drugs with N-vinylpyrrolidone.

A study has been made of the behaviour of the drugs dipyridamole and mopidamol (RA 233) attached to poly(N-vinylpyrrolidone). The inhibitory activities towards platelet aggregation induced by ADP or platelet activation factor (PAF) in sheep plasma have been examined and found to exceed the activities of the parent drugs, by factors up to 20. At the same time the abilities of the polymer-bound drugs in potentiating prostaglandin-type anti-aggregatory activities are much lower than those of the unattached drugs. The observations are explained in terms of polymer adsorption on to the platelet membranes, producing a high surface concentration of the drugs with consequent high inhibitory action. Intracellular action, such as the inhibition of phosphodiesterase, is reduced by the difficulty experienced by the polymeric drug in passing through the membrane, so that potentiation of prostaglandin activity, particularly against PAF, becomes small. A terpolymer containing units of dipyridamole and the prostaglandin analogue 5-(6-carboxyhexyl)-1-(3-cyclohexyl-3-hydroxypropyl)hydantoin (245C) shows a degree of 'self-potentiation'.

Adenosine Diphosphate↗
PubMed1986

Polymeric inhibitors of platelet aggregation. Synergistic effects and proposals for a new mechanism.

We have studied the inhibition of ADP-induced platelet aggregation in sheep platelet-rich plasma by water-soluble polymers bound to the prostaglandin analogue 5-(6-carboxyhexyl)-1-(3-cyclohexyl-3-hydroxypropyl)hydantoin ('BW 245' C, (I). The use of unambiguous modes of binding this antiplatelet drug to polymers has enabled us to study some structural features which influence inhibitory activity. Evidence is adduced which indicates that the chemical mechanisms responsible for inhibition by free and coupled BW 245 are similar. The most important observation is a remarkable synergism demonstrated by the greatly enhanced activity of a mixture of a polymer coupled to BW 245 with the uncoupled parent polymer. In some cases (e.g., with high-molecular-weight dextran) the effect may reach (and possibly exceed) two orders of magnitude. The influence of polymer molecular weights and 'cross-polymer' effects have both been examined. A mechanism has been proposed to account for these phenomena, involving adsorption of the added (inactive) polymer on to the platelet membranes, facilitating interaction of the polymer-bound drug with receptors, made more accessible by alteration to the surface geometry. This mechanism is based on physical processes, unlike other explanations of synergistic behaviour, e.g., that of prostaglandins used in conjunction with non-polymeric drugs. The observed dependences of synergistic effects upon polymer molecular weight and type and distribution of drug molecules along chains are typical 'polymer' phenomena which are all consistent with the proposed mechanism.

Adenosine Diphosphate↗
PubMed1984

Interaction of a polymeric biguanide biocide with phospholipid membranes.

Differential scanning calorimetry (DSC) and fluorescence polarization methods have been used to study the interactions between phospholipid membranes and a polymeric biocide, poly(hexamethylene biguanide hydrochloride) (PHMB). It was found that PHMB had very little effect on neutral lipids such as phosphatidylcholine (PC) and phosphatidylethanolamine (PE), whereas it greatly reduced the phase transition temperature of phosphatidylglycerol (PG), an acidic lipid found in bacteria. Although the corresponding monomeric biocide had a similar effect on the PG bilayer, the behaviour towards mixed lipid bilayers of PC and PG has been shown to be completely different for the polymeric and monomeric biocides: viz. the former can induce isothermal phase separation into a PHMB-PG complex domain and a PC-enriched domain, whilst the latter cannot. This may account for the great difference in bactericidal activity between them. It is suggested that PHMB interacts primarily with negatively charged species in the membranes, inducing aggregation of acidic lipids in the vicinity of the adsorption site, where higher fluidity and higher permeability are expected. The results have shown that two factors might be crucial in the cidal activity of such types of cationic disinfectants as biguanides: phase separation and interaction with the hydrocarbon interior of the membranes. Polymeric biocides could be particularly effective by virtue of their ability to combine hydrophobic character and multiple charges within a single molecule.

Biguanides↗