Anatomy of heat waves and mortality in Toronto: lessons for public health protection

BACKGROUND: Periods of unusually hot weather, especially in temperate climates, carry with them a burden of morbidity and mortality, particularly in urban areas. With lessening debate on its origins, and signs of global warming already apparent, it is becoming imperative for public health practitioners to recognize and predict the risks of "heat waves", and to develop protective community responses to them. This study makes use of historical data and a methodology developed previously to examine the pattern of hot weather experienced over the last five decades in the City of Toronto, and to assess the associated burden of mortality. METHODS: Synoptic classification of air masses based on meteorological data for Toronto was used, to assign the annual mean burden of illness (in terms of elevated mortality) associated with hot weather and air pollution. Then, coefficients relating daily mortality risk to historical daily weather and air quality data were determined with a model system that (for each air mass) assessed the factors that contributed to day-to-day variability in mortality. RESULTS: Over the period of study, there were 120 (95% CI: 105-135) heat-related deaths on average per year, with great variability from year to year, reflecting the variability of hot weather. Mortality was greatest in July and August, when the greatest number of multi-day heat episodes occurred. Furthermore, the longer the episode, the greater was the daily risk for mortality. INTERPRETATION: The method can be used to forecast the risk of heat-related mortality, and to facilitate the development of public health responses to mitigate that risk.     

Nurses'' beliefs about the conditions that hinder or support evidence-based nursing

The aim of this study was to identify the conditions that Australian nurses believe support or hinder the development of evidence-based nursing. A survey instrument was developed from the results of content analysis of the UK and the USA research and of interviews with 12 Australian nurses. Eight hundred and sixteen nurses working in three large hospitals responded representing a response rate of 65%. Principal axis factor analysis of the survey results revealed six conditions that the participants believed were necessary for evidence-based nursing to take place. The results of this study may be used to develop models for the improvement of evidence-based nursing in Australia.     

2-Methylthioadenosine[beta-32P]diphosphate. An agonist and radioligand for the receptor that inhibits the accumulation of cyclic AMP in intact blood platelets.

2-Methylthio-ADP and its radioactive analogue [beta-32P]2-methylthio-ADP were synthesized and used to investigate platelet receptors for ADP. 2-Methylthio-ADP induced platelet aggregation and shape change, and inhibited cyclic AMP accumulation in platelets exposed to prostaglandin E1. Compared with ADP, 2-methylthio-ADP was 3-5 times as active as an aggregating agent and 150-200 times as active as an inhibitor of cyclic AMP accumulation. Binding of [beta-32P]2-methylthio-ADP to platelets was measured after centrifuging them through silicone oil to separate platelets from their suspension medium. Binding was reversible, saturable, and specific, with between 400 and 1,200 sites/cell in different platelet preparations. There was no evidence for a second class of binding sites with different affinity. The second order association rate constant was approximately 3.5 X 10(6) M-1 S-1, and the first order dissociation rate was 0.024 s-1, both measured at 23 degrees C. The dissociation equilibrium constant (approximately 15 nM) was about three times higher than the concentration giving half-maximal inhibition of prostaglandin E1-stimulated cyclic AMP accumulation in platelet-rich plasma. Binding was inhibited by ADP (Ki = 3.5 microM), ATP (7 microM), 2-azido-ADP (0.12 microM), inosine diphosphate (IDP, 150 microM), guanosine diphosphate (GDP, 350 microM), and AMP (800 microM). Binding of 2-methylthio-ADP was also blocked by the non-cell-penetrating thiol reagent, p-mercuribenzene sulphonate, a reagent that blocks the inhibition of adenylate cyclase by ADP, but which does not block the ability of ADP to induce aggregation or platelet shape change. The amount of 2-methylthio-ADP bound at saturation was independent of pH in the range 6-8, but the affinity was reduced at pH 6 compared with pH 6.5-8.0. The dissociation constant was not temperature dependent in the range 32 degrees -40 degrees C, whereas the rate of dissociation of 2-methylthio-ADP from platelets after the addition of an excess of ADP approximately doubled over this range. The activation energy for dissociation was approximately 15 kcal/mol. Our results support the conclusion that platelets have a receptor for ADP, which inhibits cyclic AMP accumulation, and which has a sulphydryl group in the binding pocket.     

Aetiology and outcome of severe community-acquired pneumonia

Between January 1972 and December 1981, 50 patients with severe community-acquired pneumonia were admitted to the intensive care unit of a district general hospital. A causal pathogen was identified in 41 cases (82%). Streptococcus pneumoniae (16 cases), Legionella pneumophila (15 cases) and Staphylococcus aureus (5 cases) were the commonest. Assisted ventilation was required in 44 patients, of whom 25 died (57%). All 5 patients with staphylococcal pneumonia and 12(75%) with pneumococcal pneumonia died. Only 5 (33%) with Legionnaires' disease died. Mortality was significantly associated with age. Recommendations for the management of severe pneumonia are made.     

Variable patterns of ST-T abnormalities in patients with left ventricular hypertrophy and normal coronary arteries.

BACKGROUND--Classically, the ST-T configuration in the electrocardiogram of patients with left ventricular hypertrophy is said to have a typical pattern of ST depression together with asymmetrical T wave inversion (the so-called left ventricular strain pattern). However, many patients with left ventricular hypertrophy may also have ischaemic heart disease. To revise the electrocardiographic criteria for left ventricular hypertrophy the ST-T configuration in patients with left ventricular hypertrophy documented by echocardiography and with normal coronary arteries was assessed. METHODS--24 patients were selected for this study. All had left ventricular hypertrophy documented by echocardiography, normal coronary arteries by cardiac catheterisation, and ST and/or T wave abnormalities in the lateral leads of their electrocardiogram. There were eight patients with aortic valve disease and 16 with hypertension who had coronary angiography as part of an investigation into the risk factors of sudden cardiac death caused by hypertensive left ventricular hypertrophy. No patient was receiving digitalis preparations or had electrolyte disturbances, and none had a previous myocardial infarction or ventricular conduction defect. RESULTS--Typical electrocardiographic evidence of left ventricular strain was found in approximately two thirds (63%) of patients and 95% of this subgroup had asymmetrical T wave inversion. Flat ST segment depression, with or without T wave inversion or isolated T wave inversion (symmetrical or asymmetrical) in the anterolateral leads, was seen in the remaining 37% of patients. CONCLUSIONS--These findings indicate that left ventricular hypertrophy without coronary artery disease can cause variable types of ST-T abnormalities in the anterolateral leads including the typical left ventricular strain pattern and non-specific ST-T changes. Non-specific abnormalities could not be distinguished from those of coronary artery disease and may adversely affect the accuracy of the electrocardiographic criteria for the diagnosis of left ventricular hypertrophy because they do not accord with the criteria for left ventricular strain.     

The association between chronic widespread pain and mental disorder: a population-based study

OBJECTIVE: Patients with chronic widespread pain (CWP) have been reported to have a greater prevalence of mental disorders and somatization than that found in the general population, but the true association between CWP and mental disorders is unknown. In this study, we investigated whether there is an increased prevalence of mental disorder in people with CWP from the general population. We also describe the psychiatric diagnoses associated with CWP. METHODS: In a population-based case-control study, 1,953 subjects (75% of a random sample of individuals age 18-65 years) completed a questionnaire that included a pain assessment and the 12-item General Health Questionnaire (GHQ-12). Of 710 subjects scoring >1 on the GHQ-12, 301 were assessed further using a structured psychiatric interview and detailed assessment of medical records to identify cases of mental disorder, in accordance with criteria of the 10th edition of the International Classification of Diseases. The association between CWP and mental disorder was modeled using logistic regression, adjusting for possible confounders including age, sex, and nonresponders. RESULTS: We estimated the overall population prevalence of mental illness to be 11.9%. The odds of having a mental disorder for subjects with versus those without CWP were 3.18 (95% confidence interval 1.97-5.11). Most subjects with mental disorders were diagnosed as having mood and anxiety disorders. Only 3 cases of somatoform disorders were identified, and all were associated with pain. CONCLUSION: This study, although unable to demonstrate a cause-and-effect relationship, showed that 16.9% of those with CWP were estimated to have a psychiatric diagnosis, suggesting that these disorders should be identified and treated.     

Heart rate, ischaemic heart disease, and sudden cardiac death in middle-aged British men.

OBJECTIVE--To examine the relation between resting heart rate and new major ischaemic heart disease events in middle aged men with and without pre-existing ischaemic heart disease. DESIGN--Prospective study of a cohort of men with eight years follow up for cardiovascular morbidity and mortality for all men. SETTING--General practices in 24 British towns (the British Regional Heart study). SUBJECTS--7735 men aged 40-59 years drawn at random from the age-sex registers of one general practice in each town. MAIN OUTCOME MEASURES--Major ischaemic heart disease events such as sudden cardiac death, other deaths attributed to ischaemic heart disease, and non-fatal myocardial infarction. RESULTS--During the follow up period of eight years, 488 men had a major ischaemic heart disease event (217 fatal and 271 non-fatal). Of these, 117 were classified as sudden cardiac death (death within one hour of the start of symptoms). The relation between heart rate and risk of all major ischaemic heart disease events, ischaemic heart disease deaths, and sudden cardiac death was examined separately in men with and without pre-existing ischaemic heart disease. In men with no evidence of ischaemic heart disease, there was a strong positive association between resting heart rate and age adjusted rates of all major ischaemic heart disease events (fatal and non-fatal), ischaemic heart disease deaths, and sudden cardiac death. This association remained significant even after adjustment for age, systolic blood pressure, blood cholesterol, smoking, social class, heavy drinking, and physical activity, with particularly high risk in those with heart rate > or = 90 beats/min. The increased risk seen in those with increased heart rate was largely due to a significantly increased risk of sudden cardiac death, which was five times higher than in those with heart rate < 60 beats/min. The effect of heart rate on sudden cardiac death was present irrespective of blood pressure or smoking state. In men with pre-existing ischaemic heart disease a positive association was seen between raised heart rate and risk of all major ischaemic heart disease events, ischaemic heart disease death, and sudden cardiac death, but the effect was less noticeable than in men without pre-existing ischaemic heart disease. CONCLUSION--In this study of middle aged British men increased heart rate > or = 90 beats/min) is a risk factor for fatal ischaemic heart disease events but particularly for sudden cardiac death. The effect is not dependent on the presence of other established coronary risk factors and is most clearly seen in men free of pre-existing ischaemic heart disease at initial examination.