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Biomedical subjects

A Dobson

Publications and source records attributed to A Dobson.

At least 19 recordsLinked to original sources
PubMed1996

Relations of changes in coronary disease rates and changes in risk factor levels: methodological issues and a practical example.

One of the main hypotheses of the World Health Organization (WHO) MONICA Project is that trends in the major coronary disease risk factors are related to trends in rates of fatal and non-fatal coronary disease events. The units of study are populations rather than individuals. The WHO MONICA Project involves continuous monitoring of all coronary disease events in the populations over a 10-year period and periodic risk factor surveys in random samples of the same populations. Estimation of associations between average annual changes in mortality and risk factor levels is illustrated with the use of data from a subset of MONICA centers. Crude estimates of regression coefficients are compared with estimates obtained by weighting for standard errors in both the outcome and explanatory variables. The results show that the strength of association may be either underestimated or overestimated if these errors are not taken into account.

Adult↗
PubMed1996

Physical medicine and rehabilitation workforce study: the supply of and demand for physiatrists.

OBJECTIVE: Analysis, results, and implications of a supply and demand workforce model for physical medicine and rehabilitation. Explicit issues addressed include: (1) the supply implications of maintaining current (1994-1995) output of physiatrists from residency programs; (2) the implications of continued growth in managed care on the demand for the services of physiatrists; (3) likely future supply and demand conditions; and (4) strategies to adapt to future conditions. DESIGN: A workforce model of the supply and demand for physiatrists was developed. Parameters of the model are estimated using econometric models and by applying the judgments of a consensus panel. The model evaluated several different scenarios regarding managed care growth, competition from other providers and other factors. RESULTS: Based on the analysis, physiatrists will continue to be in excess demand through the year 2000. More aggressive growth in managed care can affect this result. CONCLUSIONS: Based on an overall assessment of supply and demand conditions, and under the assumption that the supply of new entrants each year remains in the range of 1994-1995 levels, demand for physiatrists will continue to exceed supply, on average, through the year 2000. Excess supply has, and will, emerge in selected geographic areas. If the profession is successful in informing the market regarding the advantages of physiatry, the profession can continue to grow without experiencing excess supply, in the aggregate, for the foreseeable future.

Forecasting↗
PubMed1996

Risk factors for peptic ulcer in Shanghai.

OBJECTIVES: To investigate the combined effects of Helicobacter pylori infection and traditional risk factors for peptic ulcer. METHODS: A case-control study was conducted in chemical factories in Shanghai, China. The cases were 500 people with peptic ulcer randomly selected from all staff who met the selection criteria. The controls were 500 employees randomly selected from the same factories as the cases. RESULTS: The infection rate for H. pylori was 81% among the cases and 70% among the controls and 85% of all ulcers were duodenal. Current cigarette smoking was common among male cases (80%) and male controls (64%). Univariate analysis suggested that male gender, age, lower socioeconomic status, cigarette smoking, family history of peptic ulcer and infection with H. pylori were all associated with increased risk of peptic ulcer. Separate analyses were performed by sex and occupational group to avoid confounding by cigarette smoking and age. Multivariate analyses showed that for all women and for male staff members, only family history was significantly predictive of peptic ulcer or duodenal ulcer. Among male workers or drivers, however, all the major risk factors were statistically significantly associated with increased risk. CONCLUSIONS: In a population where the rate of infection with H. pylori is high, the traditional risk factors for peptic ulcer or duodenal ulcer (i.e. family history, male gender, increasing age, lower socioeconomic status and cigarette smoking) are still significant predictors of increased risk of ulcer. If men with ulcers (or with a family history of peptic ulcer) gave up cigarette smoking, morbidity could be reduced in this population.

Adult↗
PubMed1995

Persistence and transmission of tick-borne viruses: Ixodes ricinus and louping-ill virus in red grouse populations.

The population dynamics of tick-borne disease agents and in particular the mechanisms which influence their persistence are examined with reference to the flavivirus that causes louping-ill in red grouse and sheep. Pockets of infection cause heavy mortality and the infection probably persists as a consequence of immigration of susceptible hosts. Seroprevalence is positively associated with temporal variations in vectors per host, although variation between areas is associated with the abundance of mountain hares. The presence of alternative tick hosts, particularly large mammals, provides additional hosts for increasing tick abundance. Grouse alone can not support the vectors and the pathogen but both can persist when a non-viraemic mammalian host supports the tick population and a sufficiently high number of nymphs bite grouse. These alternative hosts may also amplify virus through non-viraemic transmission by the process of co-feeding, although the relative significance of this has yet to be determined. Another possible route of infection is through the ingestion of vectors when feeding or preening. Trans-ovarial transmission is a potentially important mechanism for virus persistence but has not been recorded with louping-ill and Ixodes ricinus. The influence of non-viraemic hosts, both in the multiplication of vectors and the amplification of virus through non-viraemic transmission are considered significant for virus persistence.

Animals↗
PubMed1995

QT dispersion does not predict early ventricular fibrillation after acute myocardial infarction.

Ventricular arrhythmias may be associated with increased QT dispersion (difference between maximum and minimum QT on standard 12-lead ECG). We performed a case control study to determine if QT dispersion on the admission ECG could predict early VF after acute myocardial infarction. The cases were 24 patients with acute myocardial infarction (14 inferior, 8 anterior, and 2 lateral) with VF within 12 hours of admission. There were 24 control patients without VF matched for site of infarction and ST segment score (sum of ST segment elevation). VF occurred a median of 153 minutes (interquartile range 93-245) after onset of chest pain and 33 minutes (range 7-104) after initial ECG. QT (399 +/- 37 and 394 +/- 37), QT corrected (440 +/- 38 and 429 +/- 29), and QT dispersion (68 +/- 20 and 66 +/- 27) were similar in patients and controls. By design, ST score was similar (11 +/- 9 vs 9 +/- 5 mV), although a good match could not be obtained for three patients with extreme ST elevation. Patients with VF presented to the hospital earlier after the onset of chest pain (median 95 min [range 65-188] compared to 150 min [range 80-270], P = 0.05) and had a lower serum sodium (138 +/- 2.4 vs 140 +/- 2.5, P = 0.05) than controls. Thus, QT interval and QT dispersion, measured on the presenting ECG, did not predict early VF after myocardial infarction.

Aged↗
PubMed1995

Metabolic adaptations for desert survival in the Bedouin goat.

Energy conservation is a key adaptation for desert survival in the Bedouin goat. When food is scarce, metabolism is reduced and body weight can be maintained indefinitely on less than one-half of normal intake. We hypothesized that metabolism would be turned down during both rest and exercise, but it was not. It was low when animals rested and returned to normal during exercise. We expected catecholamines and thyroid hormones would modulate metabolism, but they did not. The reduction in metabolism preceded any change in thyroid hormone concentrations, and infusions of epinephrine did not restore reduced metabolism to normal levels. Finally, we expected the gut would be the major organ system involved in the metabolic reduction because less food is eaten, processed, and absorbed. Contrary to our expectations, we found that muscle is the primary organ system responsible for the reduction. It appears that the adaptations of the Bedouin goat for surviving on limited food supplies involve different organ systems and different modulators to reduce metabolism from those known for other mammals.

Adaptation, Physiological↗
PubMed1994

The population dynamics of parasitic helminth communities.

This paper describes a mathematical model which allows us to compare the data collected from short-term cross-sectional surveys with the population dynamics of host and parasite populations over longer periods of time. The model extends an earlier framework for two parasite species in one host, to one for an arbitrary number of parasite species. We show that the conditions necessary for the coexistence of two parasite species extend to expressions for the coexistence of three or more parasite species. Furthermore, the model suggests that those species which form the 'core' of the parasite community are those whose high fecundity and transmission efficiency permit them to colonize hosts readily. In contrast, those species which are classified as 'satellite' species of the community are either species with low fecundity, or low transmission efficiencies. This work confirms earlier studies that suggest that increasing degrees of aggregation are crucial in allowing several species of parasites to coexist in the same species of hosts. The properties of the model are compared with patterns observed in data collected for helminth parasites of Anolis lizards, wood mice and eels. This combined theoretical and empirical approach confirms the importance of the life history strategies of the parasite in determining the abundance of each species in the community. It suggests that studies of parasite community structure have to pay more attention to the strategies pursued by each individual species before interactions between species are considered.

Animals↗
PubMed1994

An examination of winners and losers under Medicare's prospective payment system.

Through case studies of 10 matched pairs of winner and loser hospitals under the Medicare prospective payment system (PPS), specific characteristics and management actions were identified that are related to strong financial performance. Because other payers are increasingly adopting PPS-like cost control incentives and because managed care is fundamental to the national health care reform debate, the successful strategies identified in this article may be of increasing importance to hospital managers.

Cost Control↗
PubMed1993

Biodiversity.

Explore the source record for details and available documents.

Animals↗
PubMed1993

Variability in the risk of major gastrointestinal complications from nonaspirin nonsteroidal anti-inflammatory drugs.

BACKGROUND: We have assessed the extent to which the risk of serious gastrointestinal complications from nonaspirin nonsteroidal anti-inflammatory drugs (NANSAIDs) varies with the age and sex of recipients, use of aspirin or alcohol, administration by the oral or rectal route, and dose and choice of drug. METHODS: A case-control study was performed with prospective recruitment of cases of gastrointestinal bleeding or ulcer perforation and age- and sex-matched controls. Information on preadmission drug use obtained by structured interview. RESULTS: Six hundred forty-four patients and 1268 controls were recruited. The odds ratio for upper gastrointestinal complications in users compared with nonusers of NANSAIDs increased with age: < or = 59 years, odds ratio 2.0; 60-79 years, odds ratio 3.0; > or = 80 years, odds ratio 4.2; and was higher in women (5.4) than in men (1.9). There was a linear dose-response curve that was steeper in women than in men. Combined exposure suggested additive risks: NANSAIDs and aspirin, odds ratio 6.7; NANSAIDs and alcohol, odds ratio 6.0 NANSAIDs by the oral route were associated with an odds ratio of 2.3, compared with 11.4 with rectal administration. Piroxicam was associated with the highest risk, odds ratio 4.8; and ibuprofen the lowest risk, odds ratio 0.7. CONCLUSIONS: A number of factors can alter the risk of major gastrointestinal complications with NANSAIDs and need to be considered when individual prescribing decisions are made.

Administration, Oral↗
PubMed1993

Coronary heart disease case fatality in four countries. A community study. The Acute Myocardial Infarction Register Teams of Auckland, Augsburg, Bremen, FINMONICA, Newcastle, and Perth.

BACKGROUND: Community-based registers participating in the MONICA Project of the World Health Organization show markedly different attack and death rates of coronary heart disease. This variation is a function of both the incidence and case fatality occurring within countries. The contribution of case fatality to the international variation in coronary heart disease mortality rates is not well understood. METHODS AND RESULTS: The register data from eight study populations--Augsburg and Bremen in Germany, Auckland in New Zealand, Perth and Newcastle in Australia, and North Karelia, Kuopio, and Turku/Loimaa in Finland--were compared. All patients with definite myocardial infarction or coronary death aged 35 to 64 years occurring in the study populations in 1985 through 1989 are the basis for the case fatality calculations by different definitions: 28-day case fatality for all cases, for hospitalized cases, and for hospitalized 24-hour survivors; out-of-hospital case fatality; and 24-hour case fatality for hospitalized cases. Differences in case fatality were much smaller than differences in attack and mortality rates in these populations. About two thirds of deaths occurred before the patients reached a hospital. The 28-day case fatality ranged from 37% for men in Perth to 58% for women in Augsburg. Among those who reached the hospital alive, 28-day case fatality was 13% to 27% for men and 20% to 35% for women. In those who survived 24 hours from the onset of symptoms, 28-day case fatality was 8% to 17% for men and 12% to 26% for women. CONCLUSIONS: Differences in case fatality were not associated with differences in coronary mortality rates between these populations. As most deaths occurred before reaching a hospital, opportunities for reducing case fatality through improved hospital care are limited. This emphasizes the primary role of prevention in reducing coronary death rates.

Adult↗
PubMed1992

Effects of prior use of non-steroidal anti-inflammatory drugs on renal function and transfusion requirements after upper gastrointestinal haemorrhage.

The possibility has been investigated that, after admission to hospital with acute upper gastrointestinal bleeding, patients who have been users of aspirin and non-aspirin non-steroidal anti-inflammatory drugs have poorer baseline renal function, a greater improvement in renal function during their hospital stay, and a larger transfusion requirement than non-users. Patients over 50 years of age admitted to public hospitals with acute upper gastrointestinal bleeding were studied. Creatinine clearance was estimated from serum creatinine and the transfusion requirement was recorded as the number of units of blood transfused on Day 1 and throughout the entire hospital stay. Data were obtained prospectively from case notes and by structured interview. Users of non-steroidal anti-inflammatory drugs were significantly older than non-users. The estimated creatinine clearance on admission to hospital declined with age. Creatinine clearance was 13.2 (95% CI 6.0 to 20.4) ml.min-1 lower in users than non-users of non-aspirin non-steroidal anti-inflammatory drugs. However, the difference was attributable to the older age of the drug users rather than to the drugs themselves. On average, the increase in creatinine clearance during hospital stay was the same in users and non-users of non-aspirin non-steroidal anti-inflammatory drugs. Prior use of aspirin had no effect on any measure of renal function. The incidence of blood transfusion was higher in older than in younger patients but neither the incidence of transfusion, nor the transfusion requirement, was different between users and non-users of non-aspirin non-steroidal anti-inflammatory drugs and aspirin.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1992

The role of federal waivers in the health policy process.

Federal waiver programs enable states to bypass the requirements of federal programs such as Medicare and Medicaid to experiment with different ways of financing, organizing, and delivering health care. In tracking waiver activity from 1980 to 1990, the authors found that federal involvement with waivers lost momentum during the latter part of the 1980s, while state involvement increased. Three key issues dominate the discussion of waivers: administrative control, the role of the states, and the ability to evaluate demonstration waivers. Examination of the chronology of waiver activity suggests the emergence of a new era, wherein federal control reemerges as a way to counter the increased fragmentation of health policies among states. If this is the case, four areas need to be addressed: (1) balance of political and research objectives; (2) administrative flexibility for states; (3) careful scrutiny of rules; and (4) increased accountability. These recommendations can guide the federal government, with the states as partners, in its attempt to regain momentum in the use of waivers to expand the knowledge base.

Health Policy↗
PubMed1991

Sequences downstream from the transcriptional start site are essential for microaerobic, but not symbiotic, expression of the Rhizobium meliloti nifHDK promoter.

Deletion analysis studies have been carried out on the nifHDK promoter (P1) of R. meliloti in an attempt to determine sequences involved in the expression of this promoter under both free-living microaerobic and symbiotic conditions. Deletion of a region downstream (+17 to +61) from the promoter element resulted in low levels of expression under free-living microaerobic conditions. However, wild-type levels of expression were obtained during symbiosis with Alfalfa plants. The sequences in this region were designated the "downstream sequences'. The pattern of expression observed when the downstream sequences were deleted was similar to that observed when a previously identified upstream activator sequence (UAS) was deleted. Only when both the downstream sequences and the UAS were deleted, did activity from the P1 promoter become significantly decreased during symbiosis. Expression studies of the P1 promoter in a nifA mutant background indicate that nifA is required for symbiotic expression of P1 which is enhanced by the presence of the downstream sequences.

Aerobiosis↗