[1998 Quebec Social and Health Survey: determinants of chronic respiratory diseases]

In the course of the "1998 Health and Social Survey", questions were included to verify the prevalence of chronic respiratory diseases and also of wheezing. The objectives of this study were 1) to verify the prevalence of wheezing and its validity as an indicator of chronic respiratory diseases in Québec; and 2) to examine the relationship between chronic respiratory diseases and some of their potential determinants. A total of 30,386 individuals participated in the study. For all ages, the prevalence of wheezing was 5.4%. It was associated with asthma, allergies, chronic bronchitis and emphysema. A low familial income and tobacco smoking were associated with wheezing, asthma, chronic bronchitis and emphysema. Passive smoking was associated with wheezing whereas the presence of carpets was associated with wheezing and asthma. Between 32 and 48% of families with an asthmatic or an allergic member modified their dwelling to alleviate respiratory problems. The prevalence of wheezing documented here was lower than in anglosaxon countries. This result could be explained by a cultural factor (the French translation or the perception of wheezing). This study emphasizes the role of reducing tobacco smoking in the prevention of chronic respiratory diseases.

[High dose therapy with autologous stem cell support--finally a progress in myelomatosis]

BACKGROUND

Since the introduction of the simple cyclic oral treatment with melphalan and prednisone in the late 1960s, there has been no substantial improvement in the therapy of multiple myeloma. In 1994, the Nordic Myeloma Study Group initiated a population-based, prospective study to evaluate the impact on survival of high dose chemotherapy in newly diagnosed, symptomatic patients under 60 years of age, compared to a conventionally treated control group.

MATERIAL AND METHODS

274 patients were treated according to a specified high dose protocol and compared to 274 patients from previous population-based trials fulfilling the same eligibility criteria.

RESULTS

Median survival was 44 months in the control group and 62 months in the intensive treatment group (risk ratio 1.65; 95% CI = 1.28-2.14, P = 0.0001). A study of health-related quality of life (HRQoL) which was integrated in the trial showed a moderately reduced HRQoL associated with the intensive treatment phase, but no statistically significant difference beyond the first year of follow-up. In a cost-utility analysis of the trial, the cost per (quality-adjusted life years) was estimated at USD 26,000.

INTERPRETATION

The incremental cost of the treatment is within what is usually thought to be acceptable limits. Further improvement of the results and reduction of stay in hospital would give an even more favourable cost-utility ratio.

Prevalence of bronchial hyperresponsiveness among HIV-infected men

HIV infection is associated with immune dysregulation primarily affecting T-cell function, whereas asthma is related to excessive T-cell activity. We compared the prevalence of asthma and related conditions among adult seropositive men with the prevalence among men of similar age drawn from the general population. Seropositive men had a significantly more frequent occurrence of wheezing (54.4 versus 21.2%), bronchial hyperresponsiveness (BHR) to methacholine (26.2 versus 14.4%), and an elevated total serum IgE (37.8 versus 25.7%). Differences in BHR were significant only among smokers. Among the seropositive men, FEV(1)/FVC and an elevated IgE were the principal determinants of BHR. Our results suggest that the frequency of asthma may be underestimated in HIV disease. Furthermore, the frequent occurrence of BHR in HIV-infected men who smoke (30.1%) suggests this group may be especially susceptible to the adverse effects of cigarette smoke.

Identification of persons with cardiorespiratory conditions who are at risk of dying from the acute effects of ambient air particles

This study was undertaken to identify subgroups of the population susceptible to the effects of ambient air particles. Fixed-site air pollution monitors in Montreal, Quebec, Canada, provided daily mean levels of various measures of particulates and gaseous pollutants. Total sulfates were also measured daily (1986-1993) at a monitoring station 150 km southeast of the city (Sutton, Quebec, Canada). We used coefficient of haze (COH), extinction coefficient, and Sutton sulfates to predict fine particles and sulfates from a fine particles model for days that were missing. We used the universal Quebec medicare system to obtain billings and prescriptions for each Montreal resident who died in the city from 1984 to 1993. These data were then used to define cardiovascular and respiratory conditions that subjects had before death. Using standard Poisson regression time-series analyses, we estimated the association between daily nonaccidental mortality and daily concentrations of particles in the ambient air among persons with cardiovascular and respiratory conditions diagnosed before death. We found no persuasive evidence that daily mortality increased when ambient air particles were elevated for subgroups of persons with chronic upper respiratory diseases, airways disease, cerebrovascular diseases, acute coronary artery disease, and hypertension. However, we found that daily mortality increased linearly as concentrations of particles increased for persons who had acute lower respiratory diseases, chronic coronary artery diseases (especially in the elderly), and congestive heart failure. For this latter set of conditions, the mean percent increase in daily mortality (MPC) for an increase in the COH across its interquartile range (18.5 COH units per 327.8 linear meters), averaged over the day of death and the 2 preceding days, was MPC = 5.09% [95% confidence interval (CI) 2.47-7.79%], MPC = 2.62 (95% CI 0.53-4.75%), and MPC = 4.99 (95% CI 2.44-7.60%), respectively. Adjustments for gaseous pollutants generally attenuated these associations, although the general pattern of increased daily mortality remained. In addition, there appeared to be a stronger association in the summer season. The positive associations found for persons who had acute lower respiratory diseases and congestive heart failure are consistent with some prevailing hypotheses and may also be consistent with recent toxicologic data implicating endothelins. Further epidemiologic studies are required to confirm these findings.

Down-regulation of TDT transcription in CD4(+)CD8(+) thymocytes by Ikaros proteins in direct competition with an Ets activator

Ikaros is a unique regulator of lymphopoiesis that associates with pericentromeric heterochromatin and has been implicated in heritable gene inactivation. Binding and competition experiments demonstrate that Ikaros dimers compete with an Ets activator for occupancy of the lymphocyte-specific TdT promoter. Mutations that selectively disrupt Ikaros binding to an integrated TdT promoter had no effect on promoter function in a CD4(+)CD8(+) thymocyte line. However, these mutations abolished down-regulation on differentiation, providing evidence that Ikaros plays a direct role in repression. Reduced access to restriction enzyme cleavage suggested that chromatin alterations accompany down-regulation. The Ikaros-dependent down-regulation event and the observed chromatin alterations appear to precede pericentromeric repositioning. Current models propose that the functions of Ikaros should be disrupted by a small isoform that retains the dimerization domain and lacks the DNA-binding domain. Surprisingly, in the CD4(+)CD8(+) thymocyte line, overexpression of a small Ikaros isoform had no effect on differentiation or on the pericentromeric targeting and DNA-binding properties of Ikaros. Rather, the small isoform assembled into multimeric complexes with DNA-bound Ikaros at the pericentromeric foci. The capacity for in vivo multimer formation suggests that interactions between Ikaros dimers bound to the TdT promoter and those bound to pericentromeric repeat sequences may contribute to the pericentromeric repositioning of the inactive gene.

What is new since the last (1999) Canadian Asthma Consensus Guidelines?

The objective of the present document is to review the impact of new information on the recommendations made in the last (1999) Canadian Asthma Consensus Guidelines. It includes relevant published studies and observations or comments regarding what are considered to be the main issues in asthma management in children and adults in office, emergency department, hospital and clinical settings. Asthma is still insufficiently controlled in a large number of patients, and practice guidelines need to be integrated better with current care. This report re-emphasises the need for the following: objective measures of airflow obstruction to confirm the diagnosis of asthma suggested by the clinical evaluation; identification of contributing factors; and the establishment of a treatment plan to rapidly obtain and maintain optimal asthma control according to specific criteria. Recent publications support the essential role of asthma education and environmental control in asthma management. They further support the role of inhaled corticosteroids as the mainstay of anti-inflammatory therapy of asthma, and of both long acting beta2-agonists and leukotriene antagonists as effective means to improve asthma control when inhaled corticosteroids are insufficient. New developments, such as combination therapy, and recent major trials, such as the Children's Asthma Management Project (CAMP) study, are discussed.

Control of asthma in Canada: failure to achieve guideline targets

OBJECTIVE

To assess the degree of asthma control achieved by patients with asthma in Canada and to describe the impact of poor asthma control.

DESIGN

Population-based, cross-sectional telephone interview survey of Canadians with doctor-diagnosed asthma.

SUBJECTS AND METHODS

Random digit dialing was used to identify a representative sample of Canadians with asthma. A total of 801 adults and 200 parents of children aged four to 15 years were interviewed over the telephone. Telephone interviews were also conducted with 266 physicians.

RESULTS

Only 24% of patients achieved disease control by meeting the six symptom-based criteria listed by the 1996 Canadian Asthma Consensus Guidelines as appropriate treatment targets. Fifty-seven per cent of patients failed to meet two or more of the six control criteria and were considered poorly controlled. Fifty-one per cent had required urgent care for out of control asthma at least once in the year before the survey. Nonetheless, 91% of patients thought that their asthma was adequately controlled. Physicians shared this optimism: 77% of family physicians and 90% of respirologists believed that they were usually able to achieve optimal asthma control in their patients. Few physicians gauged asthma control by tracking more than one or two symptoms, and just over one-half (54%) of patients surveyed recalled ever having had a lung function test. One-half (48%) of patients with poorly controlled asthma who used inhaled steroids did not understand the role of inhaled steroids; one-third (32%) of patients with poorly controlled asthma who used short acting bronchodilators misunderstood the action of quick relief bronchodilators.

CONCLUSIONS

The majority of Canadians with asthma suffer from inadequate control of their disease. Suboptimal control of asthma is associated with excess health care use. Inadequate monitoring by physicians and poor patient education may be factors contributing to this problem.

Inhaled corticosteroids: impact on asthma morbidity and mortality

Inhaled corticosteroids are now recommended as first-line therapy for asthma. Although these drugs clearly improve the symptoms of the disease and the associated physiologic abnormalities, epidemiologic studies provide important information on their effectiveness in preventing asthma morbidity and mortality. We review the evidence regarding the role of inhaled corticosteroids in the prevention of asthma fatality and hospitalization. In the process, we discuss the methodologic complexities of the nonexperimental studies and the implications of the methodologic issues on the evaluation of the impact of these drugs. Eight of the cohort and ecologic studies conducted to date strongly suggest that inhaled corticosteroids, when taken regularly, decrease the number of hospitalizations for asthma by up to 80%. For asthma death, the results of 11 investigations appear less consistent, especially those of several cohort and case-control studies whose principal objective was to examine not the benefit of inhaled corticosteroids but the adverse effects of other drug classes. Much of the inconsistency in the results, however, can be explained by weaknesses in study design and analysis-in particular, the failure to consider exposure in terms of regular use of inhaled corticosteroids. When the most recent study involving the use of the Saskatchewan databases is considered, it is evident that regular treatment with conventional or low-dose inhaled cortico-steroids results in a significant reduction in fatalities due to asthma. In all, the evidence to date strongly indicates that regular use of inhaled corticosteroids, even at low doses, would prevent the major portion of asthma hospitalizations and deaths.

Prevalence of asthma symptoms among adults aged 20-44 years in Canada

BACKGROUND

Reported prevalence rates of asthma vary within and between countries around the world. These differences suggest environmental factors in addition to genetic factors in the cause of the disease and may provide clues for preventive strategies. We examined the variability of asthma-related symptoms and medication use among adults in 6 sites across Canada (Vancouver, Winnipeg, Hamilton, Montreal, Halifax and Prince Edward Island) and compared our findings with those from sites that had participated in a recent European survey.

METHODS

We used the same sampling strategy and standardized questionnaire as those used in the European Community Respiratory Health Survey (ECRHS). The 6 Canadian sites were selected to represent different environments with respect to climate, air pollution and occupational exposure. Community-based samples of 3000 to 4000 people aged 20-44 years were randomly selected in each site. Subjects were asked to complete the questionnaire by mail between March 1993 and November 1994. Prevalence rates (and 95% confidence intervals [CIs]) of asthma symptoms, self-reported asthma attacks and use of asthma medication were compared across the Canadian sites and with sites that had participated in the ECRHS.

RESULTS

The overall response rate of those selected to receive the questionnaire was 86.5% (range 74.5%-92.8%). The prevalence rates of most asthma symptoms varied significantly among the Canadian sites. For instance, 21.9% (Montreal) to 30.4% (Halifax) of the men and 24.0% (Vancouver) to 35.2% (Halifax) of the women reported wheezing in the year before the survey. Depending on the site, 4.4% to 6.3% of the men and 5.2% to 9.5% of the women reported an asthma attack in the last year, and 4.0% to 6.1% of the men and 4.9% to 9.7% of the women were currently using asthma medication. Prevalence rates of symptoms, asthma attacks and medication use did not change with age, but they were higher among women than among men. Compared with the results from the ECRHS sites, those from the Canadian sites were among the highest.

INTERPRETATION

Significant variation in the prevalence of asthma symptoms, asthma attacks and use of asthma medication between Canadian sites and international sites suggests environmental influences. Different combinations of factors in different sites may be responsible for the high prevalence rates and should be the subject of further research to guide clinical management and public health intervention.

MLL and CREB bind cooperatively to the nuclear coactivator CREB-binding protein

A fragment of the mixed-lineage leukemia (MLL) gene (Mll, HRX, ALL-1) was identified in a yeast genetic screen designed to isolate proteins that interact with the CREB-CREB-binding protein (CBP) complex. When tested for binding to CREB or CBP individually, this MLL fragment interacted directly with CBP, but not with CREB. In vitro binding experiments refined the minimal region of interaction to amino acids 2829 to 2883 of MLL, a potent transcriptional activation domain, and amino acids 581 to 687 of CBP (the CREB-binding or KIX domain). The transactivation activity of MLL was dependent on CBP, as either adenovirus E1A expression, which inhibits CBP activity, or alteration of MLL residues important for CBP interaction proved effective at inhibiting MLL-mediated transactivation. Single amino acid substitutions within the MLL activation domain revealed that five hydrophobic residues, potentially forming a hydrophobic face of an amphipathic helix, were critical for the interaction of MLL with CBP. Using purified components, we found that the MLL activation domain facilitated the binding of CBP to phosphorylated CREB. In contrast with paradigms in which factors compete for limiting quantities of CBP, these results reveal that two distinct transcription factor activation domains can cooperatively target the same motif on CBP.

The impact of combined inhaled bronchodilator therapy in the treatment of COPD

BACKGROUND

Treatment guidelines recommend concomitant use of ipratropium bromide and inhaled beta2-agonists as severity of COPD progresses. While the use of these two agents in a single inhaler may enhance patient compliance and result in cost savings, it may, by itself, increase medication use. We assessed whether the introduction of a combined inhaled bronchodilator in the treatment of COPD modifies the use and costs related to prescribed medications.

METHOD

A cohort of subjects > or =45 years old initiating treatment with either a combined inhaled bronchodilator (641 subjects) or ipratropium bromide and inhaled beta2 -agonist (411 subjects) between July 1, 1996, and June 30, 1997, was identified using the Saskatchewan Health databases. The primary outcomes were prescribed medication usage and the subsequent related costs during a 1-year follow-up period. Poisson regression analysis was used to estimate rate ratios (RRs) adjusted for drug use and hospitalization during the year prior to cohort entry.

RESULTS

The adjusted RR of inhaled bronchodilator use was elevated for combined inhaled bronchodilator therapy (adjusted RR, 1.16; 95% confidence interval [CI], 1.07 to 1.26). However, the overall costs associated with these inhaled bronchodilators were reduced with combined inhaled bronchodilator therapy (adjusted mean ratio, 0.83; 95% CI, 0.76 to 0.92). The rate of use of other respiratory drugs and antibiotics was similar (adjusted RR, 1.03; 95% CI, 0.93 to 1.16). Applying the rate ratio for cost savings to all new, combined inhaled bronchodilator users led to estimated annual savings in Canadian dollars of 103,468 dollars (95% CI, 48,694 dollars to 146,082 dollars) in this province.

CONCLUSION

The introduction of a simpler bronchodilator dosing regimen did not significantly alter the treatment of COPD and resulted in appreciable cost savings.

Occupational asthma in adults in six Canadian communities

We examined the prevalence, population attributable risk (PAR), and clinical characteristics of occupational asthma (OA) in a randomly selected population in six communities in Canada. Our study followed the European Community Respiratory Health Survey protocol. A randomly selected population of 18,701 (87% response rate) persons from the study communities, ranging in age from 20 to 44 yr, completed an initial questionnaire, of whom 2,974 (39% response rate) attended the laboratory and completed supplementary questionnaires. Of these latter individuals, 383 had asthma. Asthma was defined as physician-diagnosed asthma, and adult-onset asthma was defined as a first attack at age 15 yr or older. We used several methods for estimating OA as follows: (1) reporting of a high-risk job (occupation and industry) for OA at the time of asthma onset (Probable OA); (2) reporting of exposure to a substance that may cause OA (Possible OA) while not in a high-risk job at the time of asthma onset; and (3) combination of the PAR for high-risk jobs and exposures. The prevalence (95% confidence interval [CI]) of Probable OA and Possible OA combined was 36.1% (31.3 to 41.0%) among subjects with adult-onset asthma. The occupations most commonly reported in association with OA were nursing in the Probable OA group and clerical and food preparation in the Possible OA group. The clinical characteristics and exposures reported by both groups were similar. The PAR for adult-onset asthma in high-risk jobs and exposures was 18.2%. The assessment of occupation and industry alone, rather than of exposures, may underestimate the contribution of occupational exposures to asthma prevalence.

Identifying subgroups of the general population that may be susceptible to short-term increases in particulate air pollution: a time-series study in Montreal, Quebec

This study was undertaken in order to shed light on which groups of the general population may be susceptible to the effects of ambient particles. The objectives of the study were (1) to determine whether concentrations of particles in the ambient air of Montreal, Quebec, were associated with daily all-cause and cause-specific mortality in the period 1984 to 1993, and (2) to determine whether groups of the population had higher than average risks of death from exposure to particles. From the network of fixed-site air pollution monitors in Montreal we obtained daily mean levels of various measures of particles, gaseous pollutants, and weather variables measured at Dorval International Airport. We also used measurements of sulfate from an acid rain monitoring station 150 km southeast of the city (Sutton, Quebec). We estimated associations for particulate matter (PM) with an aerodynamic diameter of 10 microns or smaller (PM10), or 2.5 microns or smaller (PM2.5), total suspended particles (TSP), coefficient of haze (COH), an extinction coefficient, and sulfate. Because substantial data for fine particles were missing, we developed a regression model to predict PM2.5 and to predict sulfate from PM2.5. In the main body of the report, we present results for COH, predicted PM2.5, and sulfate. Detailed results for all pollutants are included in Appendices H through O, which are available on request from Health Effects Institute and from the HEI web site at www.healtheffects.org. To address the first objective, we made use of the underlying causes of death among all 140,939 residents of Montreal who died between 1984 and 1993. We regressed the logarithm of daily counts of cause-specific mortality on the daily mean levels for a variety of measures of particles, accounting for seasonal and subseasonal fluctuations in the mortality time series, overdispersion, and weather factors. To address the second objective, we developed algorithms to define conditions that subjects had prior to death, with the focus on cardiopulmonary diseases. These algorithms were based on information retained on the databases of the universal Quebec Health Insurance Plan (QHIP). The databases include records of all procedures (e.g., type of surgery), physician visits, and consultations carried out by all physicians in Quebec. For persons > or = 65 years and for all recipients of social assistance the prescription database contains records of all pharmaceuticals dispensed (type of medication, dose, quantity). For each group of conditions defined, we used the same statistical model that was used in the analyses of all nonaccidental causes of death. In the analyses of cause-specific mortality, we found evidence of associations for all nonaccidental causes of death and specific causes of death--cancer, coronary artery disease, respiratory diseases, and diabetes--that were consistent across most metrics of ambient air particle concentrations, evaluated as the 3-day mean of particle concentrations measured on the day of death (lag 0) and on each of the two days before death (lag 1, lag 2). Associations for all cardiovascular diseases combined were found only with sulfate. As well, we generally found increased daily mortality for persons 65 years of age and over. The results for all nonaccidental causes of death are similar to findings from other studies; the mean percent increase in mortality for a 100 micrograms/m3 increase in daily TSP at lag 0 was 6.7%. In the analyses of the groups defined from the QHIP data, there was little evidence of associations with air pollutants among persons who before death were classified as having acute or chronic upper respiratory diseases, airways diseases, hypertension, acute coronary artery diseases, and cerebrovascular diseases. On the other hand, we found consistent increases across most types of ambient particles for persons who had cancer, acute lower respiratory diseases, any form of cardiovascular disease, chronic coronary artery diseases, and congestive heart failure. As well, we found an association for individuals who did not have any cardiovascular disease, lower respiratory diseases, and cancer. This latter group consisted of persons who had no interactions with the health care system one year before death (12%) and individuals with a wide variety of potentially fatal diseases (52%), including neurological conditions (12%), diabetes (8%), cardiac dysrhythmias (8%), dementia (6%), organic psychotic disorders (6%), and anemias (4%). As statistical power was reduced in the analyses presented above, differences between groups (e.g., < 65 and > or = 65 year age groups) were not usually statistically significant. The association with diabetes has not been reported previously, and this needs to be replicated in other studies. (ABSTRACT TRUNCATED)

Low-dose inhaled corticosteroids and the prevention of death from asthma

BACKGROUND

Although inhaled corticosteroids are effective for the treatment of asthma, it is uncertain whether their use can prevent death from asthma.

METHODS

We used the Saskatchewan Health data bases to form a population-based cohort of all subjects from 5 through 44 years of age who were using antiasthma drugs during the period from 1975 through 1991. We followed subjects until the end of 1997, their 55th birthday, death, emigration, or termination of health insurance coverage; whichever came first. We conducted a nested case-control study in which subjects who died of asthma were matched with controls within the cohort according to the length of follow-up at the time of death of the case patient (the index date), the date of study entry, and the severity of asthma. We calculated rate ratios after adjustment for the subject's age and sex; the number of prescriptions of theophylline, nebulized and oral beta-adrenergic agonists, and oral corticosteroids in the year before the index date; the number of canisters of inhaled beta-adrenergic agonists used in the year before the index date; and the number of hospitalizations for asthma in the two years before the index date.

RESULTS

The cohort consisted of 30,569 subjects. Of the 562 deaths, 77 were classified as due to asthma. We matched the 66 subjects who died of asthma for whom there were complete data with 2681 controls. Fifty-three percent of the case patients and 46 percent of the control patients had used inhaled corticosteroids in the previous year, most commonly low-dose beclomethasone. The mean number of canisters was 1.18 for the patients who died and 1.57 for the controls. On the basis of a continuous dose-response analysis, we calculated that the rate of death from asthma decreased by 21 percent with each additional canister of inhaled corticosteroids used in the previous year (adjusted rate ratio, 0.79; 95 percent confidence interval, 0.65 to 0.97). The rate of death from asthma during the first three months after discontinuation of inhaled corticosteroids was higher than the rate among patients who continued to use the drugs.

CONCLUSIONS

The regular use of low-dose inhaled corticosteroids is associated with a decreased risk of death from asthma.

Autologous stem cell transplantation as post-remission therapy in adult acute myelogenous leukemia: does platelet contamination of peripheral blood mobilized stem cell grafts influence the risk of leukemia relapse?

Conventional chemotherapy of acute myelogenous leukemia (AML) results in an overall long-term disease-free survival of less than 50%, but for selected subsets of younger patients the prognosis can be improved by allogeneic stem cell transplantation. The use of autologous stem cell transplantation is now investigated as an alternative to allotransplantation due to its lower risk of serious complications. However, autotransplantation is associated with a relatively high risk of post-transplant AML relapse that can be derived from contaminating leukemia cells in the autograft. Peripheral blood mobilized stem cell (PBSC) grafts usually contain a higher number of platelets. The degree of platelet contamination is determined by the peripheral blood platelet count at the time of harvesting, and the platelets become activated and release soluble mediators during the ex vivo handling of PBSC grafts. Many of these platelet-derived mediators can bind to specific receptors expressed by AML blasts, and the platelet contamination may then alter AML blast survival and thereby influence the risk of post-transplant leukemia relapse. Therefore, we conclude that the platelet contamination of autologous stem cell grafts is possibly of clinical importance, but the effect of this nonstandardized parameter is difficult to predict in individual patients because the number of graft-contaminating platelets, the degree of platelet activation, and the effects of platelet-derived mediators on AML blasts differ between patients.

Agreement in measuring socio-economic status: area-based versus individual measures

Area-based socio-economic status (SES) measures are frequently used in epidemiology. Such an approach assumes socio-economic homogeneity within an area. To quantify the agreement between area-based SES measures and SES assessed at the individual level, we conducted a cross-sectional study of 943 children who resided in 155 small enumeration areas and 117 census tracts from 18 schools in Montreal, Quebec. We used street address information together with 1986 census data and parental occupation to establish area-based and individual level SES indicators, respectively. As compared with the SES score determined at the level of the individual, 13 different area-based SES indices classified the children within the same quintile 28.7% (+/- 2.8%) of the time. The discrepancy was within one quintile in 35.3% (+/- 2.3%) of cases, two quintiles in 20.6% (+/- 3.6%), three quintiles in 11.3% (+/- 4.2%) and four quintiles in 4.1% (+/- 0.2%). In conclusion, we observed a substantial discrepancy between area- based SES measures and SES assessed at the individual level. Caution should therefore be used in designing or interpreting the results of studies in which area-based SES measures are used to test hypotheses or control for confounding.

Relative scarcity of asthma and atopy among rural adolescents raised on a farm

We determined the prevalence of markers of atopy and asthma among 1, 199 rural secondary school students ages 12 to 19 yr. Subjects identified as having been raised on a farm and half as many subjects without regular exposure to a farming environment from the same school class completed a respiratory symptom questionnaire and underwent allergy skin tests and a methacholine bronchoprovocation test. Current wheeze, airways hyperresponsiveness (AHR), and skin test positivity to inhaled allergens were all significantly less common among adolescents raised on the farm and these differences were especially pronounced in girls. After adjusting for gender and current smoking, the odds ratios for being raised on a farm were: 0. 70 (95% CI 0.52 to 0.95) for current wheeze; 0.59 (95% CI 0.37 to 0. 95) for asthma, defined as the concomitant occurrence of wheeze and AHR; and 0.58 (95% CI 0.46 to 0.75) for atopy defined as a positive reaction to any one of 24 common inhaled allergens. These associations were also not significantly altered by adjusting for the difference in the number of siblings.

Prostaglandin H synthase 2 expression in airway cells from patients with asthma and chronic obstructive pulmonary disease

Products of the prostaglandin H synthase (PGHS) metabolic pathway are thought to play a role in the pathogenesis of asthma. We determined the level of expression of the constitutive (PGHS-1) and inducible (PGHS-2) isoforms of the enzyme in induced sputum and bronchial biopsies of patients with asthma, patients with chronic obstructive pulmonary disease (COPD), and unaffected control subjects by immunocyto- and immunohistochemistry. Immunoreactivity for PGHS-2 was significantly greater in the induced sputum of patients with asthma and patients with COPD compared with unaffected control subjects. The level of PGHS-2 was greater in asthma than in COPD. Immunoreactivity for PGHS-1 increased in cells in the induced sputum of patients with asthma and patients with COPD compared with that of unaffected control subjects. Immunostained cells included macrophages, eosinophils, and neutrophils. Greater PGHS-2 immunoreactivity was seen in the submucosal inflammatory infiltrate and in the airway epithelium of patients with asthma compared with unaffected control subjects. In summary, we demonstrate an induction of PGHS-2 in asthma, suggesting increased formation of prostanoids, which may contribute to the inflammatory process.

Mammalian Trithorax and polycomb-group homologues are antagonistic regulators of homeotic development

Control of cell identity during development is specified in large part by the unique expression patterns of multiple homeobox-containing (Hox) genes in specific segments of an embryo. Trithorax and Polycomb-group (Trx-G and Pc-G) proteins in Drosophila maintain Hox expression or repression, respectively. Mixed lineage leukemia (MLL) is frequently involved in chromosomal translocations associated with acute leukemia and is the one established mammalian homologue of Trx. Bmi-1 was first identified as a collaborator in c-myc-induced murine lymphomagenesis and is homologous to the Drosophila Pc-G member Posterior sex combs. Here, we note the axial-skeletal transformations and altered Hox expression patterns of Mll-deficient and Bmi-1-deficient mice were normalized when both Mll and Bmi-1 were deleted, demonstrating their antagonistic role in determining segmental identity. Embryonic fibroblasts from Mll-deficient compared with Bmi-1-deficient mice demonstrate reciprocal regulation of Hox genes as well as an integrated Hoxc8-lacZ reporter construct. Reexpression of MLL was able to overcome repression, rescuing expression of Hoxc8-lacZ in Mll-deficient cells. Consistent with this, MLL and BMI-I display discrete subnuclear colocalization. Although Drosophila Pc-G and Trx-G members have been shown to maintain a previously established transcriptional pattern, we demonstrate that MLL can also dynamically regulate a target Hox gene.

Canadian Asthma Consensus Report, 1999. Canadian Asthma Consensus Group

OBJECTIVES

To provide physicians with current guidelines for the diagnosis and optimal management of asthma in children and adults, including pregnant women and the elderly, in office, emergency department, hospital and clinic settings.

OPTIONS

The consensus group considered the roles of education, avoidance of provocative environmental and other factors, diverse pharmacotherapies, delivery devices and emergency and in-hospital management of asthma.

OUTCOMES

Provision of the best control of asthma by confirmation of the diagnosis using objective measures, rapid achievement and maintenance of control and regular follow-up.

EVIDENCE

The key diagnostic and therapeutic recommendations are based on the 1995 Canadian guidelines and a critical review of the literature by small groups before a full meeting of the consensus group. Recommendations are graded according to 5 levels of evidence. Differences of opinion were resolved by consensus following discussion.

VALUES

Respirologists, immunoallergists, pediatricians and emergency and family physicians gave prime consideration to the achievement and maintenance of optimal control of asthma through avoidance of environmental inciters, education of patients and the lowest effective regime of pharmacotherapy to reduce morbidity and mortality.

BENEFITS, HARMS AND COSTS

Adherence to the guidelines should be accompanied by significant reduction in patients' symptoms, reduced morbidity and mortality, fewer emergency and hospital admissions, fewer adverse side-effects from medications, better quality of life for patients and reduced costs.

RECOMMENDATIONS

Recommendations are included in each section of the report. In summary, after a diagnosis of asthma is made based on clinical evaluation, including demonstration of variable airflow obstruction, and contributing factors are identified, a treatment plan is established to obtain and maintain optimal asthma control. The main components of treatment are patient education, environmental control, pharmacotherapy tailored to the individual and regular follow-up.

VALIDATION

The recommendations were distributed to the members of the Canadian Thoracic Society Asthma and Standards Committees, as well as members of the board of the Canadian Thoracic Society. In addition, collaborating groups representing the Canadian Association of Emergency Physicians, the Canadian College of Family Physicians, the Canadian Paediatric Society and the Canadian Society of Allergy and Immunology were asked to validate the recommendations. The recommendations were discussed at regional meetings throughout Canada. They were also compared with the recommendations of other similar groups in other countries. DISSEMINATION AND IMPLEMENTATION: An implementation committee has established a strategy for disseminating these guidelines to physicians, other health professionals and patients and for developing tools and means that will help integrate the recommendations into current asthma care. The plan is outlined in this report.

Case-control study of lung cancer among sugar cane farmers in India

OBJECTIVES

To investigate the risk of lung cancer among sugar cane farmers and sugar mill workers.

METHODS

A case-control study was conducted based in six hospitals in the predominantly sugar cane farming districts of the province of Maharashtra in India. Newly diagnosed, histologically confirmed cases were identified from these hospitals between May 1996 and April 1998. Other cancers were chosen as controls and matched to cases by age, sex, district of residence, and timing of diagnosis.

RESULTS

Adjusting for confounders, an increased risk of lung cancer was found for workers ever employed on a sugar cane farm (odds ratio (OR) 1.92, 95% confidence interval (95% CI) 1.08 to 3.40). Increased risks were found for work involving preparation of the farm (OR 1.81, 95% CI 0.99 to 3.27) and burning of the farm after harvesting (OR 1.82, 95% CI 0.99 to 3.34). Non-significant increases in risks were found for harvesting the crop (OR 1.41, 95% CI 0.70 to 2.90) and processing the cane in the mills (OR 1.70, 95% CI 0.20 to 12.60).

CONCLUSIONS

Exposure to fibres of biogenic amorphous silica (BAS) formed from silica absorbed from the soil and deposited in the leaves of the sugar cane crop or crystalline silica formed as a result of conversion of BAS to cristobalite at high temperatures may account for the increased risks of lung cancer among sugar cane farmers.