Robert E. Dales

Overdiagnosis of asthma in obese and nonobese adults

Background: It is unclear whether asthma is overdiagnosed in developed countries, particularly among obese individuals, who may be more likely than nonobese people to experience dyspnea. Methods: We conducted a longitudinal study involving nonobese (body mass index 20–25) and obese (body mass index ≥ 30) individuals with asthma that had been diagnosed by a physician. Participants were recruited from 8 Canadian cities by means of random-digit dialing. A diagnosis of current asthma was excluded in those who did not have evidence of acute worsening of asthma symptoms, reversible airflow obstruction or bronchial hyperresponsiveness, despite being weaned off asthma medications. We stopped asthma medications in those in whom a diagnosis of asthma was excluded and assessed their clinical outcomes over 6 months. Results: Of 540 individuals with physician-diagnosed asthma who participated in the study, 496 (242 obese and 254 nonobese) could be conclusively assessed for a diagnosis of asthma. Asthma was ultimately excluded in 31.8% (95% confidence interval [CI] 26.3%–37.9%) in the obese group and in 28.7% (95% CI 23.5%–34.6%) in the nonobese group. Overdiagnosis of asthma was no more likely to occur among obese individuals than among nonobese individuals (p = 0.46). Of those in whom asthma was excluded, 65.5% did not need to take asthma medication or seek health care services because of asthma symptoms during a 6-month follow-up period. Interpretation: About one-third of obese and nonobese individuals with physician-diagnosed asthma did not have asthma when objectively assessed. This finding suggests that, in developed countries such as Canada, asthma is overdiagnosed.

Acute Effects of Air Pollution on Pulmonary Function, Airway Inflammation, and Oxidative Stress in Asthmatic Children

Background Air pollution is associated with respiratory symptoms, lung function decrements, and hospitalizations. However, there is little information about the influence of air pollution on lung injury. Objective In this study we investigated acute effects of air pollution on pulmonary function and airway oxidative stress and inflammation in asthmatic children. Methods We studied 182 children with asthma, 9–14 years of age, for 4 weeks. Daily ambient concentrations of sulfur dioxide, nitrogen dioxide, ozone, and particulate matter ≤ 2.5 μm in aerodynamic diameter (PM2.5) were monitored from two stations. Once a week we measured spirometry and fractional exhaled nitric oxide (FeNO), and determined thiobarbituric acid reactive substances (TBARS) and 8-isoprostane—two oxidative stress markers—and interleukin-6 (IL-6) in breath condensate. We tested associations using mixed-effects regression models, adjusting for confounding variables. Results Interquartile-range increases in 3-day average SO2 (5.4 ppb), NO2 (6.8 ppb), and PM2.5 (5.4 μg/m3) were associated with decreases in forced expiratory flow between 25% and 75% of forced vital capacity, with changes being −3.1% [95% confidence interval (CI), −5.8 to −0.3], −2.8% (95% CI, −4.8 to −0.8), and −3.0% (95% CI, −4.7 to −1.2), respectively. SO2, NO2, and PM2.5 were associated with increases in TBARS, with changes being 36.2% (95% CI, 15.7 to 57.2), 21.8% (95% CI, 8.2 to 36.0), and 24.8% (95% CI, 10.8 to 39.4), respectively. Risk estimates appear to be larger in children not taking corticosteroids than in children taking corticosteroids. O3 (5.3 ppb) was not associated with health end points. FeNO, 8-isoprostane, and IL-6 were not associated with air pollutants. Conclusion Air pollution may increase airway oxidative stress and decrease small airway function of asthmatic children. Inhaled corticosteroids may reduce oxidative stress and improve airway function.

The Epidemiology of Chronic Rhinosinusitis in Canadians

Objective To study the prevalence of chronic rhinosinusitis and its risk factors among Canadians.

Association between ambient carbon monoxide levels and hospitalizations for congestive heart failure in the elderly in 10 Canadian cities

We examined the role that ambient air pollution plays in exacerbating cardiac disease by relating daily fluctuations in admissions to 134 hospitals for congestive heart failure in the elderly to daily variations in ambient concentrations of carbon monoxide, nitrogen dioxide, sulfur dioxide, ozone, and the coefficient of haze in Canadas 10 largest cities for the 11‐year period 1981–1991 inclusive. We adjusted the hospitalization time series for seasonal, subseasonal, and weekly cycles and for hospital usage patterns. The logarithm of the daily high‐hour ambient carbon monoxide concentration recorded on the day of admission displayed the strongest and most consistent association with hospitalization rates among the pollutants, after stratifying the time series by month of year and adjusting simultaneously for temperature, dew point, and the other ambient air pollutants. The relative risk for a change from 1 ppm to 3 ppm, the 25th and 75th percentiles of the exposure distribution, was 1.065 (95% confidence interval = 1.028–1.104). The regression coefficients of the other air pollutants were much more sensitive to simultaneous adjustment for either multiple pollutant or weather model specifications.

Traffic-Related Air Pollution and Acute Changes in Heart Rate Variability and Respiratory Function in Urban Cyclists

Background: Few studies have examined the acute health effects of air pollution exposures experienced while cycling in traffic. Objectives: We conducted a crossover study to examine the relationship between traffic pollution and acute changes in heart rate variability. We also collected spirometry and exhaled nitric oxide measures. Methods: Forty-two healthy adults cycled for 1 hr on high- and low-traffic routes as well as indoors. Health measures were collected before cycling and 1–4 hr after the start of cycling. Ultrafine particles (UFPs; ≤ 0.1 μm in aerodynamic diameter), particulate matter ≤ 2.5 μm in aerodynamic diameter (PM2.5), black carbon, and volatile organic compounds were measured along each cycling route, and ambient nitrogen dioxide (NO2) and ozone (O3) levels were recorded from a fixed-site monitor. Mixed-effects models were used to estimate associations between air pollutants and changes in health outcome measures relative to precycling baseline values. Results: An interquartile range increase in UFP levels (18,200/cm3) was associated with a significant decrease in high-frequency power 4 hr after the start of cycling [β = –224 msec2; 95% confidence interval (CI), –386 to –63 msec2]. Ambient NO2 levels were inversely associated with the standard deviation of normal-to-normal (NN) intervals (β = –10 msec; 95% CI, –20 to –0.34 msec) and positively associated with the ratio of low-frequency to high-frequency power (β = 1.4; 95% CI, 0.35 to 2.5) 2 hr after the start of cycling. We also observed significant inverse associations between ambient O3 levels and the root mean square of successive differences in adjacent NN intervals 3 hr after the start of cycling. Conclusions: Short-term exposures to traffic pollution may contribute to altered autonomic modulation of the heart in the hours immediately after cycling.

The role of ipratropium bromide in the emergency management of acute asthma exacerbation: a metaanalysis of randomized clinical trials.

STUDY OBJECTIVE This study was conducted to determine whether the addition of inhaled ipratropium to inhaled beta-agonist therapy is effective in the treatment of adults with acute asthma exacerbation. METHODS Published reports of randomized, controlled trials assessing the use of ipratropium and beta-agonists in asthma were identified by a search of the MEDLINE, EMBASE, CINAHL, Biological Abstracts on CD, the Cochrane Library, and Current Contents databases. Bibliographies from identified studies and from review articles were manually searched. Published and unpublished reports in English, French, and Italian were identified and assessed for inclusion in the metaanalysis. Randomized, double-blind, placebo-controlled trials were selected in which ipratropium was used as adjunctive therapy to beta-agonists in adult patients with acute asthma exacerbation presenting to a hospital emergency department or similar acute care setting. Data were extracted independently by 2 reviewers. For eligible trials, the mean percent change in peak expiratory flow rate (PEFR), or forced expiratory volume in one second (FEV1), and their SDs were assessed in the ipratropium-treated and control groups. The effect of ipratropium on hospitalization rates and adverse effects were also analyzed. RESULTS Data from 10 studies, reporting on a total of 1,377 patients with asthma, were pooled using a weighted average method. Compared with placebo, the use of ipratropium was associated with a pooled 7.3% improvement in FEV1 (95% confidence interval [CI] 3.8% to 10.9%), corresponding to an absolute improvement in FEV1 in the ipratropium/ beta-agonist group, which was 100 mL (95% CI 50 to 149 mL) above that seen for the group that received beta-agonist without ipratropium. Similarly, the pooled estimate of treatment effect in trials that reported data as PEFR was 22.1% (95% CI 11.0% to 33.2%), corresponding to an absolute peak expiratory flow improvement of 32 L/min (95% CI 16 to 47 L/min) in favor of the ipratropium/ beta-agonist combination group. When these data were combined using effect size as a common measure, the use of ipratropium was associated with a summary effect size of.38 (95% CI.27 to.48). Effect sizes were negatively correlated with baseline mean expiratory flows, suggesting that studies enrolling patients with more severe airflow obstruction showed greater absolute benefits of combination bronchodilator therapy. For the 3 trials reporting hospital admission data (n=1,031), patients receiving ipratropium had a relative risk of hospitalization of .73 (95% CI.53 to .99). The use of ipratropium was not associated with any severe adverse effects when used in conjunction with beta2 -agonists. CONCLUSION There is a modest statistical improvement in airflow obstruction when ipratropium is used as an adjunctive treatment to beta2 -agonists for the treatment of acute asthma exacerbation. Although the clinical significance of this improvement in airflow obstruction remains unclear, it would seem reasonable to recommend the use of combination ipratropium/ beta-agonist therapy in acute adult asthmatic exacerbations, since the addition of ipratropium seemed to provide physiologic evidence of benefit without risk of adverse effects.

Associations between short-term changes in nitrogen dioxide and mortality in Canadian cities.

The association between daily variations in ambient concentrations of nitrogen dioxide (NO2) and mortality was examined in 12 of Canadas largest cities, using a 19-yr time-series analysis (from 1981-1999). The authors employed parametric statistical methods that are not subject to the recently discovered convergence and error estimation problems of generalized additive models. An increase in the 3-d moving average of NO2 concentrations equivalent to the population-weighted study mean of 22.4 ppb was associated with a 2.25% (t = 4.45) increase in the daily nonaccidental mortality rate and was insensitive to adjustment for ozone, sulfur dioxide, carbon monoxide, coefficient of haze, size-fractionated particulate mass, and the sulfate ion measured on an every-6th-day sampling schedule. The 3-d moving average of NO2 was sensitive to adjustment for fine particulate matter measured daily during the 1998-2000 time period.

Quality of indoor residential air and health

About 90% of our time is spent indoors where we are exposed to chemical and biological contaminants and possibly to carcinogens. These agents may influence the risk of developing nonspecific respiratory and neurologic symptoms, allergies, asthma and lung cancer. We review the sources, health effects and control strategies for several of these agents. There are conflicting data about indoor allergens. Early exposure may increase or may decrease the risk of future sensitization. Reports of indoor moulds or dampness or both are consistently associated with increased respiratory symptoms but causality has not been established. After cigarette smoking, exposure to environmental tobacco smoke and radon are the most common causes of lung cancer. Homeowners can improve the air quality in their homes, often with relatively simple measures, which should provide health benefits.

Quality-of-life following thoracotomy for lung cancer

Contrary to the issues of perioperative morbidity and survival following surgery for lung cancer, little attention has been given to quality-of-life. To address this, quality-of-life was assessed preoperatively and 1, 3, 6 and 9 months postoperatively in a cohort of 117 consecutive subjects who underwent thoracotomy with a certain or presumptive diagnosis of lung cancer. Those with cancer (n = 91) confirmed at thoracotomy were contrasted to those without (n = 26). Moderate to severe dyspnea, reported in 14% preoperatively, increased to 34% at 1 and 3 months (p < 0.005) but returned to approximately 10% at 6 and 9 months. Similarly, activities of daily living were impaired in 11% preoperatively; this disability increased to 21% at 1 month (p < 0.005), and returned to baseline at 6 and 9 months. Those with cancer compared to those without a postoperative diagnosis of cancer had similar quality-of-life preoperatively but deteriorated more in the postoperative period. This study demonstrates that important deterioration in quality-of-life occurs during the first 3 months postoperatively in those with a final diagnosis of cancer but improvement back to baseline can be expected thereafter.

Effects of indoor, outdoor, and personal exposure to particulate air pollution on cardiovascular physiology and systemic mediators in seniors.

Objective: To investigate the associations between exposure to particulate air pollution and changes in cardiovascular function and plasma mediators in seniors. Methods: We monitored daily indoor and outdoor black carbon and particulate matter ≤2.5 &mgr;m (pm2.5) and personal pm2.5 repeatedly for 28 nonsmoking seniors. We then measured their blood pressure, heart rate, and brachial artery function, and determined plasma mediators of inflammation, vascular function, and oxidative stress. We tested associations using mixed-effects models. Results: Increases in black carbon and pm2.5 were associated with increases in blood pressure, heart rate, endothelin-1, vascular endothelial growth factor, and oxidative stress marker thiobarbituric acid reactive substances, and a decrease in brachial artery diameter (P < 0.05). Conclusion: Daily exposure to particulate pollution, likely traffic-related, may result in adverse effects on cardiovascular function and blood mediators that modulate vascular system in seniors.