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Biomedical subjects

G Hill

Publications and source records attributed to G Hill.

At least 37 records · Page 2Linked to original sources
PubMed2001

Study organization in the Canadian Study of Health and Aging.

The Canadian Study of Health and Aging was a complex undertaking that faced management challenges not encountered by smaller-scale projects. The study followed 10,263 elderly people in 18 study centers spanning six time zones; it was administered in two languages, and over 70 investigators were involved. The data collected from each participant were not fixed, but varied according to the results of earlier testing. The data could include a screening interview, a self-completed risk factor questionnaire, an interview with a relative, a clinical examination, neuropsychological testing, blood samples, and neuroimaging. This report describes the approach taken to organize the study, to track participants, and to monitor adherence to the study protocol. It also describes the human organizational aspects, including systems for staff training, for communicating among study centers, and for coordinating the publication of results. The discussion proposes some guiding principles for administering multicenter studies.

Aged↗
PubMed2001

Estimating antemortem cognitive status of deceased subjects in a longitudinal study of dementia.

There was a five-year delay between the two waves of the Canadian Study of Health and Aging during which 2,982 participants died. Their cognitive status before death should be taken into account in estimating the incidence of dementia in the cohort. Information concerning antemortem cognitive status was available from death certificates and from an interview with a close relative of the decedent at the CSHA-2 follow-up. The interview included a direct question on whether the person had been diagnosed with dementia and questions covering cognitive signs and symptoms from which we formed an algorithm to predict probability of dementia. These sources of information were validated using a small sample of study participants who died within five months of undergoing the CSHA clinical examination. Sensitivity of the death certificate and the question regarding diagnosis of dementia was low (33% and 44%), although their specificity was very high. Accordingly, we combined these with the predictive algorithm to form an overall estimate of the probability of antemortem dementia. This raised the sensitivity to 82% (specificity 93%).

Aged↗
PubMed2001

Effects of screening errors and differential mortality on the estimation of the incidence of dementia in the Canadian Study of Health and Aging.

The Canadian Study of Health and Aging produced an estimate of the incidence of dementia among elderly Canadians by following up, after 5 years, the undemented found in an initial prevalence survey. Initial and follow-up estimates could be biased by false-negative error in the screening tool used for subjects living in the community, and by erroneous classification of subjects who died in the interim. Here, we use a deterministic model to quantify those possible biases. We conclude that, using the estimates of the errors from control samples, the incidence among community subjects would be overestimated by 15%, and the incidence among the institutional subjects would be underestimated by 37%. The overall incidence would be underestimated by 14%. Most of the bias can be attributed to inaccuracies in the classification of deaths.

Aged↗
PubMed2001

The benefits of using patient-based methods of assessment. Medium-term results of an observational study of shoulder surgery.

We carried out a prospective study of 93 patients undergoing surgery for conditions of the rotator cuff during 1994 and 1995. They were assessed before operation and after six months, and four years, using the patient-based Oxford Shoulder Score (OSS), the SF-36 questionnaire and the Constant shoulder score. The response rates were higher for the OSS and SF-36. The correlation coefficients were high (r > 0.5) between all scores at each stage of the study. While all scores improved substantially at six months, the Constant score was reduced significantly at four years. This did not correlate with the patients' judgement of the change in symptoms or of the success of the operation. Our study suggests that patient-based measures of pain and function can reliably assess outcomes in the medium term after surgery to the shoulder.

Humans↗
PubMed2001

Pharmacokinetics and dosage recommendations for an oseltamivir oral suspension for the treatment of influenza in children.

OBJECTIVE: Oseltamivir (Ro 64-0796) is an ester prodrug of the active metabolite Ro 64-0802 (oseltamivir carboxylate), a potent and selective inhibitor of the neuraminidase enzyme of influenza virus. In this study we report the pharmacokinetics of oseltamivir in healthy children volunteers (study 1) and in children with influenza (study 2). STUDY PARTICIPANTS AND METHODS: In study 1, an open-label, single dose study, serial plasma samples were obtained from a total of 18 healthy children (5 to 18 years) who were grouped by age (n = 6 per group) and received single oral doses of oseltamivir 2 mg/kg. In study 2, a randomised, placebo controlled phase III study in paediatric children (1 to 12 years) presenting with influenza symptoms, 199 pharmacokinetic sparse samples were obtained from 87 patients, and serial samples were obtained from 5 patients. Pooled data were compared with those from adult studies. RESULTS: Children (1 to 12 years) eliminated the active metabolite faster than both adolescents (13 to 18 years) and adults, resulting in lower exposure to the active drug. In these children, oseltamivir 2 mg/kg twice daily resulted in drug exposures within the range associated with tolerability and efficacy in adults administered approximately 1 mg/kg twice daily. Unit doses of oseltamivir 30, 45 and 60mg oral suspension are recommended twice daily in children weighing < or =15 kg (or < or =33 lb, aged 1 to 3 years), > 15 to 23 kg (or >33 to 51 lb, aged 4 to 7 years) and >23 to 40 kg (or >51 to 88 lb, aged 8 to 12 years), respectively. A 75 mg capsule may be a viable dosage formulation in children (e.g. over 8 years of age) who are able to swallow solid dosage forms. CONCLUSIONS: Young children cleared the active metabolite oseltamivir carboxylate at a faster rate than older children and adults. Convenient administration recommendations for the oseltamivir oral suspension in children are possible to maintain drug exposure within the target window.

Acetamides↗
PubMed2000

Imaging the electron wave function in self-assembled quantum dots.

Magnetotunneling spectroscopy is used as a noninvasive and nondestructive probe to produce two-dimensional spatial images of the probability density of an electron confined in a self-assembled semiconductor quantum dot. The technique exploits the effect of the classical Lorentz force on the motion of a tunneling electron and can be regarded as the momentum (k) space analog of scanning tunneling microscopy imaging. The images reveal the elliptical symmetry of the ground state and the characteristic lobes of the higher energy states.

Journal Article↗
PubMed2000

Likelihood and clinical trials.

The history of the application of statistical theory to the analysis of clinical trials is reviewed. The current orthodoxy is a somewhat illogical hybrid of the original theory of significance tests of Edgeworth, Karl Pearson, and Fisher, and the subsequent decision theory approach of Neyman, Egon Pearson, and Wald. This hegemony is under threat from Bayesian statisticians. A third approach is that of likelihood, stemming from the work of Fisher and Barnard. This approach is illustrated using hypothetical data from the Lancet articles by Bradford Hill, which introduced clinicians to statistical theory.

Bayes Theorem↗
PubMed2000

Inverted electron-hole alignment in InAs-GaAs self-assembled quantum dots.

New information on the electron-hole wave functions in InAs-GaAs self-assembled quantum dots is deduced from Stark effect spectroscopy. Most unexpectedly it is shown that the hole is localized towards the top of the dot, above the electron, an alignment that is inverted relative to the predictions of all recent calculations. We are able to obtain new information on the structure and composition of buried quantum dots from modeling of the data. We also demonstrate that the excited state transitions arise from lateral quantization and that tuning through the inhomogeneous distribution of dot energies can be achieved by variation of electric field.

Journal Article↗
PubMed2000

Vascular dementia : incidence and risk factors in the Canadian study of health and aging.

BACKGROUND AND PURPOSE: Very few population-based studies have systematically examined incident vascular dementia (VaD). From the Canadian Study of Health and Aging cohort, incidence rates of VaD were determined and risk factors analyzed. METHODS: This was a cohort incidence study that followed 8623 subjects presumed to be free of dementia over a 5-year period. The risk factors were examined with a nested prospective case-control study. Exposure was determined by means of a risk factor questionnaire administered to the subject or a proxy at the beginning of the study. RESULTS: On the basis of 38 476 person-years at risk, the annual incidence rate was estimated to be 2.52 per thousand undemented Canadians (95% CI 2. 02 to 3.02). Including an estimation of the probability of VaD among the decedents, this figure rose to 3.79. For the risk factors study, 105 incident cases of VaD according to the NINCDS-AIREN criteria were compared with 802 control subjects. Significant risk factors were: age (OR=1.05), residing in a rural area (2.03), living in an institution (2.33), diabetes (2.15), depression (2.41), apolipoprotein E epsilon4 (2.34), hypertension for women (2.05), heart problems for men (2.52), taking aspirin (2.33), and occupational exposure to pesticides or fertilizers (2.05). Protective factors were eating shellfish (0.46) and regular exercise for women (0.46). There was no relation with sex, education, or alcohol. CONCLUSIONS: The study confirmed some previously reported risk factors but also suggested new ones. It raised concerns about the prescription of aspirin and perhaps other factors related to rural life.

Age Distribution↗
PubMed2000

Acute myocardial infarction at a university hospital: effect of race on short-term mortality.

Several studies have shown that African Americans who have an acute myocardial infarction (AMI) have a higher mortality rate and receive less aggressive cardiac intervention compared with whites. This observational study reports on the in-hospital mortality rate for AMI by race at a university tertiary referral hospital. Racial variation in clinical outcomes and treatment in the area of thrombolysis and acute revascularization was assessed. Data were retrieved from the National Registry on Myocardial Infarction (NRMI) for all 521 patients with AMI admitted to the critical care unit at the University of North Carolina between January 1991 and December 1994. Information collected included age, gender, race, cardiac catheterization results, thrombolytic therapy, coronary bypass surgery, mortality, and arrhythmia. African Americans had a lower in-hospital mortality rate compared with whites (2% versus 8% P < or = 0.03) and were also younger (61 +/- 13 SD versus 64 +/- 12 P = 0.02). Hypertension, diabetes mellitus, or prior myocardial infarction were similar in both groups. Of the 323 patients who received a cardiac catheterization, the extent of coronary disease and left ventricular ejection fraction was similar in both races. Finally, the use of thrombolysis, PTCA, or CABG was not influenced by race. In conclusion, the in-hospital mortality for African Americans at this university tertiary referral center was lower than for whites. This occurred despite a similar incidence in cardiac risk factors and similarly aggressive acute cardiac interventions in both white and African American patients. While African Americans experienced lower in-hospital mortality, this study does not address the pre-hospital and post-hospital risk. It does suggest that African Americans with AMI, who are comparably matched to whites for risk and receive similar cardiac interventions, may have a favorable in-hospital mortality.

Black or African American↗
PubMed1999

Mortality in elderly Canadians with and without dementia: a 5-year follow-up.

OBJECTIVES: Based on the national Canadian Study of Health and Aging (CSHA), to compare 5-year overall mortality and causes of death in elderly with and without dementia. To determine how frequently dementia was mentioned on the death certificate. METHODS: For people who underwent a clinical examination in 1991 (n = 2,923), overall and cause-specific mortality rate ratios were calculated by dementia status (AD; vascular dementia; other dementias/other cognitive impairment; and normal cognition), age group (65 to 74, 75 to 84, 85+ years), and sex, using the Canadian general population as the reference. Similar rate ratios were calculated for people in the community who screened negative for cognitive impairment and who did not undergo a clinical examination (n = 7,340). Among elderly diagnosed as having AD or vascular dementia through the CSHA and who later died, it was determined how frequently dementia was recorded on the death certificate. RESULTS: The subgroup without cognitive dysfunction had a survival rate similar to that of the overall Canadian population except in the oldest age group, where the survival rate was better than that of the general population, which includes people with dementia. People in the three groups with cognitive impairment had a poorer survival in all age/sex groups than those without cognitive impairment and the general Canadian population. The most common causes of death in all groups were from vascular diseases. People with vascular dementia had the highest relative mortality rates for heart and cerebrovascular disease. Most of the AD groups also had high relative vascular system mortality rates. Among patients clinically diagnosed with AD, only 14.3% had any dementing illness recorded as the underlying cause of death; 41.8% had any dementing illness recorded anywhere on the death certificate. For vascular dementia, the corresponding numbers were 5.8% and 23.3%. CONCLUSION: Elderly with dementia have clearly increased mortality rates relative to elderly without cognitive impairment in all age/sex categories. People with vascular dementia have a particularly poor prognosis. Studies of AD and vascular dementia using death certificate data will grossly underestimate the proportions of elderly with these diseases.

Aged↗
PubMed1999

Recurrent varicose veins: patterns of reflux and clinical severity.

Duplex scanning was used to determine patterns of recurrent varicose veins in 264 limbs and to relate these to clinical factors. All limbs had previously undergone sapheno-femoral ligation in the groin. A recurrent sapheno-femoral junction was present in 172 (65.2%). Incompetence was found in long or short saphenous veins in 232 limbs (87.9%), perforators in 176 (66.7%), and deep veins in 156 (59.1%). Residual long saphenous veins were present in 43.4% and 73.6% of limbs that were with and without stripped long saphenous veins, respectively. An incompetent thigh perforator was present in 14.0% and 15.3% of these two groups, respectively. Multiple sites of incompetence were observed in the majority (75.4%). In general, no particular reflux pattern in the groin was related to an increased incidence of ulceration. However, ulceration was more frequent in limbs with deep reflux to knee or below-knee levels. None of those with isolated reflux in the groin that was unrelated to the common femoral vein had ulceration. The pattern of reflux was unrelated to striping or non-striping of the long saphenous veins and the time since initial surgery. A history of deep vein thrombosis was invariably associated with some degree of deep reflux. A system of recurrent patterns in the groin is described for the purpose of surgical audit. In 15.1%, recurrence was attributed with some confidence to inadequate surgery. These results indicate that the pattern of recurrence is highly variable and often with multiple sites of incompetence. In a few instances, the pattern of recurrence was associated with specific clinical factors. A full work-up including duplex scanning is recommended.

Aged↗
PubMed1999

Predictors of five-year mortality in older Canadians: the Canadian Study of Health and Aging.

OBJECTIVE: Based on the Canadian Study of Health and Aging (CSHA), to determine the importance of cognitive status, sociodemographic factors, functional status, and other health related factors as predictors of 5-year overall mortality in older Canadians. DESIGN, SETTING AND PARTICIPANTS: Two partially overlapping groups from the Canadian Study of Health and Aging (1991) were identified: (1) older people living in the community (n = 8949) who had a screening interview (larger sample, fewer variables) and (2) older people who underwent an extensive clinical examination (smaller sample, more objective variables; n = 2914). Deaths in the subsequent 5 years were determined from death certificates and interviews with the caregivers. Multivariate logistic regression models, with death within 5 years as the outcome, were developed separately for men and women. Predictor variables were introduced in the following groups: sociodemographic factors, physical and cognitive status, and physical illnesses and life style factors. Parallel models were developed for the screening sample and for the clinical sample. RESULTS AND DISCUSSION: Five-year mortality ranged from 10.0% (women aged 65-74 living in the community) to 88.1% (men aged 85 and older living in institutions). Multivariate models showed that the odds of death within 5 years increased with age. This effect remained after adjustment for all other variables. Odds of death increased with institutionalization and with increasing cognitive and physical impairment. Although vision and hearing problems and the presence of heart disease, stroke, and diabetes were all strongly related to 5-year mortality in univariate, unadjusted analyses, their contributions were minimal in the multivariate analyses. Increased Body Mass Index was associated with lower mortality in both univariate and multivariate analyses. CONCLUSIONS: This population-based study supported the importance of gender, age, functional status, cognition, and health status in predicting 5-year mortality, and after accounting for cognitive status, physical status, and specific disease variables, the difference in mortality between older people in the community and in institutions was reduced. Knowledge about survival and prognosis is important not only for the planning of long-term facilities and home care, but it can also be helpful for clinical decision-making and for family and caregivers.

Aged↗
PubMed1999

The intrarenal vascular lesions associated with primary antiphospholipid syndrome.

Even 10 yr after the identification of the antiphospholipid syndrome (APS), renal involvement in the course of APS is still relatively unrecognized, and is probably underestimated. The association of anticardiolipin antibodies and/or lupus anticoagulant with the development of a vaso-occlusive process involving numerous organs is now confirmed. In a multicenter study, 16 cases of "primary" APS (PAPS) were found and followed for 5 yr or more, all with renal biopsy. In all 16 cases of PAPS, there was a vascular nephropathy characterized by small vessel vaso-occlusive lesions associated with fibrous intimal hyperplasia of interlobular arteries (12 patients), recanalizing thrombi in arteries and arterioles (six patients), and focal cortical atrophy (10 patients). In combination, these led to progressive destruction of the kidney, accelerated by acute glomerular and arteriolar microangiopathy in five patients. Focal cortical atrophy is a distinctive lesion, present in 10 biopsies, and likely represents the histologic and functional renal analogue to the multiple cerebral infarcts detected on imaging studies. The clinical hallmark of this vascular nephropathy in PAPS is systemic hypertension, only variably associated with renal insufficiency, proteinuria, or hematuria. The ensemble of histologic renal lesions defined in this study should aid in the separation of the lesions found in cases of secondary APS, especially systemic lupus erythematosus, into those lesions related to APS and those related to the underlying disease.

Adult↗