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Biomedical subjects

A J Dobson

Publications and source records attributed to A J Dobson.

At least 109 records · Page 6Linked to original sources
PubMed1991

The variability of immunoglobulins and albumin in salivary secretions of children.

The variation of concentrations of immunoglobulins and albumin in consecutive daily collections of saliva was studied in 33 infants, aged 6 months to 5 years, for periods ranging from 16 to 26 days. The concentration and the within-child variability of IgA and albumin and the detection of IgG and IgM in saliva increased with age. Between-child variances were greater than the within-child variances by a factor of 2.8 for log (IgA) and 1.3 for log (albumin). The geometric mean IgA levels were consistently higher and IgG was detected more frequently during upper respiratory tract infections compared with periods of non-infection. There were no changes in albumin levels between infection and non-infection periods, suggesting a local immune response rather than serum leakage. There were significant within-child correlations (autocorrelations) between levels of IgA in saliva collected on consecutive days and samples collected up to 3 days apart. The autocorrelations between levels of albumin were significant for samples collected up to 2 days apart. The autocorrelation for IgA was significantly greater during infection periods compared with non-infection periods for samples collected on consecutive days.

Age Factors↗
PubMed1990

Death from myocardial infarction: what are the benefits of early arrival at hospital and thrombolysis?

The potential benefits of early hospital care in the event of myocardial infarction were investigated in a community-based study of all suspected cases of heart attack among people aged under 70 years in the Hunter Region of New South Wales. Between August 1984 and December 1985 acute care data were collected for 1029 cardiovascular events classified as definite myocardial infarction or sudden coronary death; 516 (50%) resulted in death within 28 days from the onset of symptoms and 325 of these deaths (63%) occurred outside hospital. Of 703 people who are known to have reached hospital alive 205 (29%) did so more than four hours after the onset of symptoms. At the time of the study fewer than 1% of patients received streptokinase. To estimate the potential benefits of increased medical care an optimistic scenario was considered in which patients who arrived at hospital more than four hours after the onset of symptoms received medical attention earlier and all eligible patients received thrombolysis. Based on the results of the Second International Study of Infarct Survival (ISIS-2), if streptokinase and aspirin had been used 14% of deaths would have been averted. If, in addition, patients had arrived at hospital earlier and received optimal benefit from thrombolysis another 13% of deaths could have been avoided. These results provide a broader perspective of the potential benefits of improved medical care than can be obtained from hospital-based studies that deal only with those heart attack victims who survive long enough to reach hospital alive.

Adult↗
PubMed1990

On the use of a logistic risk score in predicting risk of coronary heart disease.

Many studies over the last 20 years have used logistic regression to model the relationship between the risk of developing coronary heart disease (CHD) and the levels of risk factors such as high blood pressure, high serum cholesterol, and cigarette smoking. Subsequently, several investigators have proposed the use of some of the published estimated logistic risk functions to predict risk in new populations. Because of great variation in definition of event, duration of follow-up, population characteristics, definition of risk variables, and selection of other variables in the logistic functions, direct use of such established functions would generally not have validity for the prediction of absolute risk levels. A review of fifteen of these studies indicates on the one hand generally similar results in direction and order of magnitude of effects of the major risk factors, confirming the importance of these risk factors of CHD. On the other hand the reviews indicate sufficient variation to suggest that extrapolation to new populations even to predict relative risk is not justified.

Age Factors↗
PubMed1990

Length of hospital stay after acute myocardial infarction.

A number of trials show that long stay in hospital after an acute myocardial infarction (AMI) is not necessary for many patients and that stays of three-ten days may be adequate. All patients aged under 70 years with a diagnosis of AMI admitted to the seven public hospitals in the Lower Hunter Region of New South Wales are monitored as part of the WHO MONICA Study. Between August 1984 and December 1985 of 438 hospitalised patients with a 'definite' AMI according to MONICA criteria and a clinical discharge diagnosis of AMI, 386 (88%) patients were discharged alive from hospital. Four patients had lengths of stay between 46 and 77 days and have been omitted from further analysis. The mean length of hospital stay was 13.6 days (95% confidence intervals 12.9 to 14.3 days); 74% of all patients stayed in hospital for more than ten days. The mean length of stay in the Coronary Care Unit (CCU) was 4.5 days (95% confidence intervals 4.2 to 4.8 days) with 60% staying longer than three days. Mean hospital stay varied from 10.5 to 17.4 days among the seven hospitals, although most of this variation was accounted for by three hospitals with few patients. Restricting analysis to the four hospitals with 90% of all the patients, multiple regression analysis showed that the CK enzyme levels, the evolution of Q waves on ECG, the presence of an anterior AMI and the use of nitrates and digoxin during hospitalisation were all associated with increased length of stay in hospital.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Methodological issues in interpreting trends in MONICA event rates.

Before looking at the trends in coronary event rates and case fatality rates in the WHO MONICA Project, it is necessary to assess the consistency and validity of the data. In the Newcastle MONICA Collaborating Centre, two methods have been used. One involves monitoring data quality by comparisons with external data systems such as hospital discharge data and official mortality records. The other is to examine the internal consistency of MONICA diagnostic findings. For fatal myocardial infarction (MI) or coronary death, there is consistent evidence of a decline, but the MONICA data are not adequate to assess relative changes in sudden compared to non-sudden death rates. For non-fatal definite MI there was an increase early in the study, possibly due to a change in methods, but rates have now stabilized. For non-fatal possible MI there has been a steady increase in rates for events which may be becoming less severe. This is consistent with increasing hospital admissions for subacute ischaemic heart disease (IHD) and angina. This paper exemplifies the importance of maintaining internal and external surveillance of the quality of the data.

Adult↗
PubMed1989

Marriage is associated with a lower risk of ischaemic heart disease in men.

Comparison between subjects who were identified from a register of cases of myocardial infarction and a random sample of the same community showed that in the Lower Hunter region of New South Wales men who currently are not married are at higher risk of acute myocardial infarction or of sudden coronary death than are married men of the same age. While there are indications that unmarried men have a life-style that is different from that of currently married men, their increased risk of ischaemic heart disease is greater than can be accounted for by differences in factors such as age, the previous history of heart disease, their alcohol and tobacco consumption and various socioeconomic factors.

Adult↗
PubMed1989

Assessing agreement.

Formal evaluation of the ability of clinicians and researchers to agree, for example, on the clinical assessment of patients, increasingly is becoming important. Two measures of agreement, kappa and the intraclass correlation coefficient, are described and illustrated. The calculation of confidence intervals that correspond to these statistics by means of the "bootstrap" method also is discussed.

Analysis of Variance↗
PubMed1989

Declining mortality from ischemic heart disease and cerebrovascular disease in Australia.

The authors examined the patterns of mortality from ischemic heart disease and cerebrovascular disease in Australia for men and women aged 30-84 years during the period 1950-1986 to assess the relative contributions of period and cohort effects on changes in the mortality rates. Death rates for ischemic heart disease increased from 1950 to the late 1960s and then declined. Although the relative magnitude of the decline was greater among younger age groups, decreasing mortality rates were experienced in all age groups, including the oldest. The period effect was dominant so that each successive cohort experienced lower age-specific mortality rates after the late 1960s. Death rates for cerebrovascular disease for both sexes and all age groups have declined since the early 1950s, although the rate of change was less in 1961-1971 and greater before and after this period. No cohort effect was demonstrated for either disease. Changes in diet, decreasing prevalence of cigarette smoking, and increasing treatment of hypertension throughout the period and improved coronary care from the late 1960s onward are all consistent with the mortality trends.

Adult↗
PubMed1989

Social effects of a history of ischaemic heart disease.

The consequences of ischaemic heart disease include adverse personal and social effects as well as morbidity and mortality. This study describes these affects among people registered in a community-based study of all suspected heart attacks. Two groups were compared, those with and those without a previous history of ischaemic heart disease, using information about the subjects' lives before the event which caused them to be registered. Men with a history were more likely to be retired or permanently unable to work (64% compared with 47%). Despite some modification of risk factors, such as reductions of cigarette smoking, men (but not women) with a history were more likely to die from the registered event especially within one hour from onset of symptoms. These results emphasize the need for prevention of heart disease before it causes the effects and disabilities reported here.

Adult↗
PubMed1988

Point estimates and confidence intervals for two-sample rank tests.

The editorial policy of most medical journals now requires authors to provide point estimates and confidence intervals in addition to P values. To compare data from two groups, the rank-sum test (for independent groups) and the signed-ranks test (for related groups) provide P values but do not give estimates for the size of the difference between the groups. Point estimates and confidence intervals, which were developed by Hodges and Lehmann, that correspond to these rank tests are described and illustrated.

Bronchitis↗
PubMed1988

A cost-effectiveness analysis of alternative strategies for the prevention of heart disease.

The identification of risk factors, such as a raised cholesterol level, hypertension, cigarette smoking, and obesity, permits the prediction of the possible development of ischaemic heart disease and has led to attempts at its prevention through modification of these factors. A high risk of developing ischaemic heart disease is also associated with age, specific socioeconomic groups, a family history of ischaemic heart disease, and preexisting evidence of the disease. Preventive strategies have either sought to reduce the average levels of risk in the general population or to identify by population screening individuals or groups who are at particular risk and to reduce their level of risk. Differing methods of risk-factor identification and modification are appropriate for each of the high-risk groups. For a number of strategies that are directed at either the whole population or high-risk groups we have estimated the costs of identification and risk-factor modification and the probable benefits of undertaking such a strategy. A strategy which educates the whole population by way of the media costs considerably less than does any strategy that involves the identification of individuals at high risk. At a medium cost estimate, with a reduction in risk of only 1%, such an approach costs approximately $8000 per case that is prevented; when risk reduction approaches 3% it actually results in a saving of health-care expenditure within five years. The costs of the other strategies vary between $12,000 and $26,000 per case that is prevented in a five-year period.

Adult↗
PubMed1988

Morphometric analysis of coronary artery stenosis: an accuracy and reliability study.

Luminal narrowing was assessed in 238 transverse segments obtained from coronary arteries removed at postmortem. In each segment, narrowing was assessed by gross visual estimation before and after fixation, and on histological sections by stereological point counting and computer-assisted planimetry. Computer-assisted planimetry was found to be accurate and reliable but the equipment needed is expensive, and requires specialized software and an experienced user. Morphometric measurement by stereologic point counting was accurate, rapid, simple, and inexpensive. In comparison with computer-assisted planimetry visual estimation was found to be neither accurate nor reliable. Our results indicate point counting as the method of choice for assessment of coronary artery luminal narrowing by atherosclerosis.

Anthropometry↗
PubMed1988

Proportional hazards models for average data for groups.

In ecological studies it is sometimes tempting to apply statistical models derived from longitudinal studies of individuals to cross-sectional data which may be available only in aggregate form for groups of individuals. This paper examines the assumptions and approximations that are made when average data for groups are used with predictive equations derived for individuals, in particular for the proportional hazards model. It is shown that this method underestimates age-specific hazard functions but that if ratios of hazard functions are used to compare groups then the approach is valid provided that certain plausible conditions hold. A numerical example is given about trends in heart disease mortality in Australia. Group data are available on risk factor levels and mortality. A proportional hazards model derived from the Framingham study is used to estimate the effects on mortality which may be attributed to risk factor changes and the effects attributable to other factors such as improved medical treatment. The interpretation of the results is discussed.

Australia↗
PubMed1988

Ischemic heart disease in the Hunter Region of New South Wales, Australia, 1979-1985.

In Australia, mortality rates from ischemic heart disease have declined by more than 40 per cent in the last 20 years. To investigate the reasons for this trend, detailed studies are being conducted in the Hunter Region of New South Wales, an area with high heart disease rates. Data on death rates and attack rates from 1979 to 1984-1985 were obtained from three sources: national mortality records, local hospital statistics, and heart disease registers conducted in 1979 and 1984-1985 using World Health Organization protocols. Age-standardized death rates from ischemic heart disease, hospitalization rates for acute myocardial infarction, and attack rates from myocardial infarction determined from the disease registers all showed declines of approximately 3-4 per cent per year from 1979 to 1985. The results differ from findings in New Zealand, where the decrease in ischemic heart disease mortality has been attributed to fewer sudden deaths. These discrepancies demonstrate the need for carefully standardized studies to gain insight into evolving patterns of heart disease in different populations.

Adult↗
PubMed1988

Coronary events in the Hunter region of New South Wales, Australia: 1984-1986.

The results of coronary event registration using the protocol of the World Health Organization MONICA Project are reported for two years for the Hunter Region, the area in and around Newcastle in New South Wales, Australia. The Newcastle MONICA Project monitors all suspected cases of heart attack by identifying patients from hospital admissions and obtaining information while they are still in hospital. For people who die out of hospital, the initial source of information is usually the death certificate. Rates for the most robust MONICA diagnostic categories, non-fatal definite myocardial infarction and all coronary deaths, differed for the two years reported here. Monthly rates suggested possible seasonal effects, and the possible influence of lower respiratory infections including an epidemic of influenza A. The results demonstrate that consistent monitoring over several years will be necessary to establish clear trends in coronary heart disease.

Adult↗
PubMed1987

Epidemiology of acquired immunodeficiency syndrome in Australia .

Since 1982, when the first case of acquired immunodeficiency syndrome (AIDS) was diagnosed in Australia, a total of 373 cases has been reported to the NHMRC Special Unit in AIDS Epidemiology and Clinical Research to December 19, 1986. Analysis of the data shows that 70% of cases were diagnosed in NSW and of all cases 88% were found to be in homosexual or bisexual men, with the majority aged between 30 and 39 years. Opportunistic infections were found in nearly three-quarters of cases. A mathematical model which has been developed predicts that 1000 cases will have been diagnosed by mid-1988 and nearly that many again in 1990 alone. The absence of a treatment or vaccine, the likelihood that current Australian resources will be inadequate to deal with the predicted number of cases, and the urgent need to establish measures that are aimed at controlling the extent of the disease are emphasized.

Acquired Immunodeficiency Syndrome↗
PubMed1987

The development of IgA-specific antibodies to Escherichia coli O antigen in children.

One hundred and sixty-five infants were studied longitudinally from birth to 5 years of age. One hundred and twenty-three school-age children and 27 adults were examined cross-sectionally. Total salivary IgA levels and IgA antibodies against Escherichia coli O antigens were measured. Total IgA levels were low (less than 20 mg/l) from birth to 4 years of age. At 5 years of age there was a dramatic increase in the total IgA level (geometric mean = 100.7 mg/l), after which the levels fell to values similar to those observed in adults (adult geometric mean = 53.2 mg/l). Low levels of IgA-specific E. coli antibodies were observed for the first 4 years of life (less than 1.0 ELISA units). There was a gradual increase in specific antibodies between 5 and 9 years of age (geometric men at 9 years = 4.66 ELISA units) to levels similar to those observed in adults (adult geometric mean = 8.20 ELISA units). It is suggested that the patterns of development for these variables reflect a balance between antigenic exposure and immune control mechanisms.

Adolescent↗