The influence of sensitisation to pollens and moulds on seasonal variations in asthma attacks.

No large study has described the seasonal variation in asthma attacks in population-based asthmatics in whom sensitisation to allergen has been measured. 2,637 young adults with asthma living in 15 countries reported the months in which they usually had attacks of asthma and had skin-prick tests performed. Differences in seasonal patterns by sensitisation status were assessed using generalised estimating equations. Most young adults with asthma reported periods of the year when their asthma attacks were more common (range: 47% in Sweden to 86% in Spain). Seasonal variation in asthma was not modified by sensitisation to house dust mite or cat allergens. Asthmatics sensitised to grass, birch and Alternaria allergens had different seasonal patterns to those not sensitised to each allergen, with some geographical variation. In southern Europe, those sensitised to grass allergens were more likely to report attacks occurred in spring or summer than in winter (OR March/April 2.60, 95% CI 1.70-3.97; OR May/June 4.43, 95% CI 2.34-8.39) and smaller later peaks were observed in northern Europe (OR May/June 1.25, 95% CI 0.60-2.64; OR July/August 1.66, 95% CI 0.89-3.10). Asthmatics reporting hay fever but who were not sensitised to grass showed no seasonal variations. Seasonal variations in asthma attacks in young adults are common and are different depending on sensitisation to outdoor, but not indoor, allergens.

Empirical treatment of community-acquired pneumonia and the development of fluoroquinolone-resistant tuberculosis.

UNLABELLED: BACKGROUND" Fluoroquinolone (FLQ) antibiotics are not uncommonly prescribed for community-acquired pneumonia that is later proven to be pulmonary tuberculosis (TB). Such FLQ monotherapy may result in FLQ-resistant pulmonary TB. METHODS: To assess outpatient FLQ use by patients with culture-proven pulmonary TB before diagnosis, TB registries in Alberta and Saskatchewan, Canada, were linked with provincial and federal drug benefit plans. To assess FLQ resistance, a case-control study was performed. RESULTS: Of 428 patients with pulmonary TB who were covered by a drug benefit plan, 74 (17.3%) had received > or = 1 FLQ prescription during the 6 months immediately before receipt of the diagnosis. Older patients (age, >64 years) were more likely than younger patients (age, 15-64 years) to be prescribed an FLQ (P < .05). Patients who were prescribed an FLQ received a total of 103 prescriptions. Most (54 [73.0%] of 74) patients who were prescribed an FLQ received a single prescription. Most (69 [67.0%] of 103) FLQ prescriptions were written within 90 days before the diagnosis of pulmonary TB. Patients who were prescribed an FLQ were not statistically significantly more likely than matched patients who were not prescribed an FLQ (control subjects) to be infected with FLQ-resistant Mycobacterium tuberculosis. Of 148 isolates of M. tuberculosis from patients and control subjects, 3 were FLQ resistant; all of these isolates were from patients who had received multiple FLQ prescriptions. Patients who had received multiple FLQ prescriptions were more likely than patients who had received a single FLQ prescription to be infected with FLQ-resistant M. tuberculosis (15.0% vs. 0.0%; odds ratio, 11.4; P = .04). CONCLUSIONS: Outpatient FLQ use, ostensibly for community-acquired pneumonia, is not uncommon among patients with pulmonary TB, especially older patients. Single FLQ prescriptions were not associated with FLQ-resistant M. tuberculosis, whereas multiple FLQ prescriptions were associated with FLQ resistance.

The feasibility of using an 'opt-out' approach to achieve universal HIV testing of tuberculosis patients in Alberta.

OBJECTIVE: Universal HIV testing of tuberculosis (TB) patients, defined as testing greater than 80% of incident cases, has been recommended but not achieved in Canada. The objectives of this study were: i) to assess the success of an 'opt-out' approach, whereby HIV testing is routine unless the patient specifically chooses otherwise, and ii) to determine the risk factors for HIV in patients tested before and after this approach was implemented. METHODS: TB and HIV databases in the province of Alberta were cross-matched before HAART (highly active anti-retroviral therapy) was available (1991-1997), after HAART but before 'opt-out' testing was implemented (1998-2002), and after 'opt-out' testing was implemented (2003-2006), and the HIV status of TB patients in each time period was described. The demographic and clinical characteristics of HIV-positive and -negative TB patients aged 15-64 years were compared. RESULTS: HIV testing of TB patients increased from 11.5% before HAART, to 44.9% after HAART but before 'opt-out' testing, to 81.9% after 'opt-out' testing was implemented. Between 1991 and 2006, 50 TB patients were diagnosed with HIV co-infection, all in the age group 15-64 years. Among TB patients aged 15-64 years who were HIV tested, those testing positive were significantly less likely to be female and to have respiratory TB and significantly more likely to have both respiratory and non-respiratory TB. The prevalence of HIV positivity in HIV-tested TB patients aged 15-64 years was 7.4% in 2003-2006. CONCLUSION: Universal HIV testing of TB patients is achievable through 'opt-out' HIV testing.

Prevalence of asthma symptoms in 7th- and 8th-grade school children in a rural region in India.

UNLABELLED: We estimated the prevalence of asthma related symptoms in grade 7 and 8 students in a rural region in India. METHOD: An International Study of Asthma and Allergies in Childhood (ISAAC), questionnaire with added questions related to environmental and familial exposures, was administered to 3668 students from 48 rural schools near Malegaon, India. RESULTS: A history of asthma was present in 10.7% students and 7.3% wheezed in the past 12 months, with about one-third having at least four attacks. Boys had the higher prevalence of all asthma-related symptoms than girls did, and symptom frequency was generally above the median reported for urban Indian ISAAC centers. Asthma and wheeze were associated with a family history of asthma, smoking, and frequent chest colds. Significant environmental factors included parental occupation and smoking and poor water sources. Increased odds of asthma occurred in students working for wages, exposed to animals, or eating in the kitchen. Relationships were similar for wheezing. Both asthma and wheeze were higher in the Scheduled Tribe (ST) group. Most markers of socioeconomic status and environmental exposure were not significant in multivariate analysis. CONCLUSION: The prevalence of asthma and wheeze in a rural region in India was similar to that found in the urban ISAAC study; it was higher in students from lower socioeconomic groups with poorer environmental conditions.

Relationship of early childhood viral exposures to respiratory symptoms, onset of possible asthma and atopy in high risk children: the Canadian Asthma Primary Prevention Study.

The contribution of respiratory viral infections to the onset of asthma and atopy is controversial. In "high risk" children (n = 455) born into asthmatic/atopic families, we determined the relationship of exposures to common respiratory viruses and concomitant respiratory symptoms, and to subsequent possible asthma and atopy at ages 1 and 2 years. Frozen nasal specimens, obtained when children were 2 weeks, 4, 8, and 12 months old, underwent reverse transcription-polymerase chain reaction (RT-PCR) testing for parainfluenza virus (PIV), respiratory syncytial virus (RSV), and picornavirus (rhinovirus/enterovirus). Odds ratios of viral RT-PCR results to respiratory symptoms ("cold," rhinitis, cough, wheezing) and to possible asthma or atopy at 1 and 2 years of age were calculated. Positive viral RT-PCR was associated with increased odds of "cold" and cough; PIV and picornavirus were associated with rhinitis, and RSV was associated with wheezing. PIV was associated with increased odds of atopy at 1 year of age in the control group; PIV and RSV were associated with possible asthma at 2 years of age. We conclude that in high-risk children, viral exposures documented by RT-PCR are associated with respiratory symptoms, and exposures to PIV and RSV during the first year of life are associated with the initial onset of possible asthma.

Airflow obstruction in young adults in Canada.

OBJECTIVE: Airflow obstruction is relatively uncommon in young adults, and may indicate potential for the development of progressive disease. The objective of the present study was to enumerate and characterize airflow obstruction in a random sample of Canadians aged 20 to 44 years. SETTING: The sample (n=2962) was drawn from six Canadian sites. DESIGN: A prevalence study using the European Community Respiratory Health Survey protocol was conducted. Airflow obstruction was assessed by spirometry. Bronchial responsiveness, skin reactivity to allergens and total serum immunoglobulin E were also measured. Logistic regression was used for analysis. RESULTS: Airflow obstruction was observed in 6.4% of the sample, not associated with sex or age. The risk of airflow obstruction increased in patients who had smoked and in patients who had lung trouble during childhood. Adjusted for smoking, the risk of airflow obstruction was elevated for subjects with past and current asthma, skin reactivity to allergens, elevated levels of total immunoglobulin E and bronchial hyper-responsiveness. Of the subjects with airflow obstruction, 21% were smokers with a history of asthma, 50% were smokers without asthma, 12% were nonsmokers with asthma and 17% were nonsmokers with no history of asthma. Bronchial hyper-responsiveness increased the prevalence of airflow obstruction in each of these groups. CONCLUSION: Smoking and asthma, jointly and individually, are major determinants of obstructive disorders in young adults. Bronchial hyper-responsiveness contributes to obstruction in both groups.

Pediatric tuberculosis in Alberta: epidemiology and case characteristics (1990-2004).

BACKGROUND: Pediatric tuberculosis (TB) is important medically and indicative of a public health problem. An understanding of the epidemiology and case characteristics of pediatric TB, in a province that accepts large numbers of immigrants, can inform TB elimination strategy. METHODS: All cases of pediatric TB notified in Alberta between 1990 and 2004 were identified in the TB Registry. Individual diagnostic criteria were reviewed and case patients were related to a population grid derived from Statistics Canada censuses and population estimates of Status Indians from the Department of Indian and Northern Affairs, Canada. Incidence rates were determined by ethnic group and gender. Clinical/mycobacteriologic case characteristics were compared by ethnic group and birth country. RESULTS: Among 124 notified cases, 95 (96 episodes) met strict diagnostic criteria: 45 Status Indians, 30 Canadian-born 'other' and 21 foreign-born. Incidence rates were much higher in Status Indians and the foreign-born compared to the Canadian-born 'other'; 10.7, 5.4, and 0.4 per 100,000 person-years, respectively. Among Canadian-born 'other' cases, 12 were Métis and 11 were Canadian-born children of foreign-born parents. Compared to foreign-born cases, Canadian-born cases were more likely to have a source case in Alberta, to be detected through contact tracing, to have primary pulmonary TB, and to have a rural address. CONCLUSION: Pediatric TB in Alberta is mainly the result of ongoing transmission in Aboriginal peoples and immigration to Canada of persons with latent TB infection. The elimination of pediatric TB will require interruption of transmission in Aboriginal peoples and prevention of disease in immigrants.

Mycobacterium tuberculosis infection in First Nations preschool children in Alberta: implications for BCG (bacille Calmette-Guérin) vaccine withdrawal.

BACKGROUND: On April 1, 2004, BCG (bacille Calmette-Guérin), a tuberculosis (TB) control vaccine, was discontinued in all but four high-risk communities in Alberta. To confirm the safety of vaccine withdrawal, and for future planning, the annual risk of infection (ARI) was determined in preschool First Nations children. METHODS: First Nations children born into reserve communities in Alberta between April 1, 1998 and March 31, 2004, and still living on reserve in 2004-2005, were identified. Health centre TB histories were validated by cross-referencing the birth cohort with the provincial TB Registry. Children that were not BCG vaccinated and not known to be tuberculin skin test (TST) positive underwent a TST. Birth cohort children were grouped as follows: (i) BCG vaccinated; (ii) BCG non-vaccinated, no TST; (iii) BCG non-vaccinated, TST; (iv) BCG vaccination status unknown. The ARI was calculated and the age and community characteristics of the groups were compared. RESULTS: There were 8447 children in the 6-year birth cohort, 4699 (55.6%) vaccinated, 2696 (31.9%) non-vaccinated, and 1052 (12.5%) whose vaccination status was unknown. Of the non-vaccinated children, 1921 (71.3%) were tested and only 2 were TST positive. No other TST positive, BCG non-vaccinated children were identified in the TB Registry cross-match. The prevalence of infection in 2004-2005 was 0.1% and the ARI was 0.03%. The community risk of TB exposure was comparable in tuberculin-tested and non-tested BCG non-vaccinated children. CONCLUSION: In low BCG-uptake First Nations communities in Alberta, the ARI is low and it is safe to withdraw BCG.

Healthcare utilization in women with obstructive sleep apnea syndrome 2 years after diagnosis and treatment.

UNLABELLED: SUBJECTIVE OBJECTIVES: To document healthcare utilization 2 years after diagnosis in women with obstructive sleep apnea syndrome (OSAS). DESIGN: Retrospective observational cohort study. SETTING: Tertiary university-based medical center. PATIENTS AND CONTROLS: Four hundred and fourteen women with OSAS were matched with 1404 women from the general population who served as controls. INTERVENTIONS: Patients were treated with continuous positive airway pressure (CPAP) or were recommended weight loss alone. MEASUREMENTS AND RESULTS: There were 231 treatment compliant (TC) patients, 91 patients not using CPAP (NCU), and 92 patients who were only recommended weight loss (WL). In the entire group, there was increase in fees of $123.43+/-$25.01 in the 2 years before diagnosis and a reduction of fees of $37.96+/-$21.35 in the 2 years after diagnosis (p < .0001). Physician claims increased in the 2 years before diagnosis by $111.22+/-31.35 in TC and by $152.77+/-59.55 in the NCU groups and then decreased in TC by $20.96+/-$26.60 (p < .01) and NCU by $72.20 +/-45.91 in the 2 years after diagnosis (p < .01). The fees in WL group did not change significantly. The number of clinic visits of the entire group increased in the 2 years before diagnosis by 2.32+/-0.43 and decreased over the next 2 years by 1.48+/-0.42 visits (p < .0001). There was an increase of clinic visits in the 3 subgroups in the 2 years before diagnosis (2.30+/-0.57 in TC, 2.55+/-0.99 in NCU, and 2.18+/-0.82 in WL groups) followed by a reduction of clinic visits over the next 2 years (1.56+/-0.55 fewer visits in TC [p < .0001], 1.70+/-0.90 in NCU [p < .01], and 1.04+/-0.90 in the WL group [p < .05] ). CONCLUSIONS: Healthcare utilization in women with OSAS increased in the years before sleep-clinic evaluation and then decreased in the following 2 years.

Estimating the incidence of dementia: the impact of adjusting for subject attrition using health care utilization data.

PURPOSE: To estimate incidence rates for dementia and the impact of subject attrition on these rates. METHODS: Crude, age- and gender-specific incidence rates of dementia and Alzheimer's disease were calculated using person-years analysis and Cox proportional hazard models in a population-based cohort study of 1952 adults aged 65+ years in Manitoba, Canada. Rates were standardized to the nondemented population using the direct method. Ratios of incidence rates comparing completers to subjects who had died, refused, or were unavailable for follow up were based on health care utilization data (available for all subject groups) and used to adjust rates for attrition. RESULTS: Decedents had a significantly higher incidence of dementia than did subjects who completed the follow-up assessment. The incidence in subjects who refused or were unavailable at follow up was intermediate between decedents and completers. Adjusted for attrition, the standardized dementia incidence rate for community and institutional subjects was 25.3/1000 person-years, significantly higher than that based on follow-up assessments only (17.8/1000 person-years; 95% confidence interval: 14.3-21.4). CONCLUSIONS: The impact of loss to follow up on incidence rates varies depending on the reason for subject attrition. Incidence studies of dementia should develop strategies to characterize and address subject attrition to avoid underestimating disease incidence.

Inhaled corticosteroids and mortality in COPD.

STUDY OBJECTIVES: To assess the influence of inhaled corticosteroids (ICSs) on mortality in COPD patients, which is currently a controversial topic. SETTING: Manitoba Health maintains a population-wide research database that includes pharmaceutical information. DESIGN AND PATIENTS: We examined mortality in people 90 to 365 days after hospital discharge for COPD, comparing those persons who received inhaled steroids within 90 days of hospital discharge with those who did not. Cox proportional hazards models were used with adjustments for other respiratory drugs, comorbidities, and physician visits before and after hospital discharge. We also compared mortality in patients who received inhaled steroids with those who received other respiratory drugs, but not inhaled steroids, and those who received neither. Using nested case control analysis, we examined the time of receipt of inhaled steroids in relation to fatal events. RESULTS: In people > 65 years of age, inhaled steroids were associated with a 25% reduction in mortality between 90 and 365 days after hospital discharge, while mortality increased with bronchodilator use, physician visits, age, and comorbidities. The exclusion of people who had also received a diagnosis of asthma or had received inhaled steroids before hospitalization did not change the result. Inhaled steroids were associated with an even larger mortality reduction in people aged 35 to 64 years. People who received bronchodilators but no steroids had higher mortality than people who received no bronchodilators or received both bronchodilators and inhaled steroids. The reduction in all-cause mortality was largely due to the decreased number of cardiovascular deaths. The receipt of inhaled steroids within 30 days of death was protective, but this was not the case for greater time intervals. CONCLUSIONS: Therapy with ICSs reduced mortality in COPD patients; the effect was particularly notable for cardiovascular death and was short term in that it was dependent on recent exposure.

The effects of a smoking cessation intervention on 14.5-year mortality: a randomized clinical trial.

BACKGROUND: Randomized clinical trials have not yet demonstrated the mortality benefit of smoking cessation. OBJECTIVE: To assess the long-term effect on mortality of a randomly applied smoking cessation program. DESIGN: The Lung Health Study was a randomized clinical trial of smoking cessation. Special intervention participants received the smoking intervention program and were compared with usual care participants. Vital status was followed up to 14.5 years. SETTING: 10 clinical centers in the United States and Canada. PATIENTS: 5887 middle-aged volunteers with asymptomatic airway obstruction. MEASUREMENTS: All-cause mortality and mortality due to cardiovascular disease, lung cancer, and other respiratory disease. INTERVENTION: The intervention was a 10-week smoking cessation program that included a strong physician message and 12 group sessions using behavior modification and nicotine gum, plus either ipratropium or a placebo inhaler. RESULTS: At 5 years, 21.7% of special intervention participants had stopped smoking since study entry compared with 5.4% of usual care participants. After up to 14.5 years of follow-up, 731 patients died: 33% of lung cancer, 22% of cardiovascular disease, 7.8% of respiratory disease other than cancer, and 2.3% of unknown causes. All-cause mortality was significantly lower in the special intervention group than in the usual care group (8.83 per 1000 person-years vs. 10.38 per 1000 person-years; P = 0.03). The hazard ratio for mortality in the usual care group compared with the special intervention group was 1.18 (95% CI, 1.02 to 1.37). Differences in death rates for both lung cancer and cardiovascular disease were greater when death rates were analyzed by smoking habit. LIMITATIONS: Results apply only to individuals with airway obstruction. CONCLUSION: Smoking cessation intervention programs can have a substantial effect on subsequent mortality, even when successful in a minority of participants.

Latitude, birth date, and allergy.

BACKGROUND: The space and time distribution of risk factors for allergic diseases may provide insights into disease mechanisms. Allergy is believed to vary by month of birth, but multinational studies taking into account latitude have not been conducted. METHODS AND FINDINGS: A questionnaire was distributed in 54 centres to a representative sample of 20- to 44-y-old men and women mainly in Europe but also including regions in North Africa, India, North America, Australia, and New Zealand. Data from 200,682 participants were analyzed. The median prevalence of allergic rhinitis was 22%, with a substantial variation across centres. Overall, allergic rhinitis decreased with geographical latitude, but there were many exceptions. No increase in prevalence during certain winters could be observed. Also, no altered risk by birth month was found, except borderline reduced risks in September and October. Effect estimates obtained by a multivariate analysis of total and specific IgE values in 18,085 individuals also excluded major birth month effects and confirmed the independent effect of language grouping. CONCLUSION: Neither time point of first exposure to certain allergens nor early infections during winter months seems to be a major factor for adult allergy. Although there might be effects of climate or environmental UV exposure by latitude, influences within language groups seem to be more important, reflecting so far unknown genetic or cultural risk factors.

Utilization of healthcare resources in obstructive sleep apnea syndrome: a 5-year follow-up study in men using CPAP.

STUDY OBJECTIVES: Patients with untreated obstructive sleep apnea syndrome (OSAS) have higher healthcare utilization than matched controls. However, the long-term impact of continuous positive airway pressure (CPAP) use on healthcare utilization is unknown. DESIGN: Retrospective observational cohort study. SUBJECTS: There were 342 eligible men with OSAS and matched controls on whom there were utilization data for 5 years prior to initial OSAS diagnosis and for the 5 years on CPAP treatment of the cases. INTERVENTIONS: Patients were treated with CPAP. RESULTS: Patients with OSAS were typical cases (mean +/- SD): age, 48.2 +/- 0.6 years; body mass index, 35.6 +/- 0.4 kg/m2; Epworth Sleepiness Scale score, 14.2 +/- 0.3; apnea-hypopnea index, 47.1 +/- 1.8 events per hour. The number of physician visits were higher by 3.46 +/- 0.2 (95% confidence interval [CI]: 2.57 to 4.36) in cases in the year before diagnosis, compared with the fifth year before diagnosis, then decreased over the next 5 years by 1.03 +/- 0.49 (95% CI: -1.99 to -0.07)(P<.0001). Physician fees, in Canadian dollars, were higher by dollars 148.65 +/- dollars 27.27 (95% CI: 95.12 to 202.10) in cases in the year before diagnosis, compared with the fifth year before diagnosis, and then decreased over the next 5 years by dollars 13.92 +/- dollars 27.94(95%CI: -68.68 to 40.83)(P=.0009). Preexisting ischemic heart disease at the time of OSAS diagnosis predicted about a 5-fold increase in healthcare utilization between the second and fifth year of treatment. CONCLUSIONS: Treatment of OSAS reversed the trend of increasing healthcare utilization seen prior to diagnosis. Preexisting ischemic heart disease results in a negative impact on healthcare utilization. CPAP results in a long-term health benefit, as measured by the use of healthcare services.

Diagnoses received by narcolepsy patients in the year prior to diagnosis by a sleep specialist.

STUDY OBJECTIVES: Narcolepsy is a neurological disorder whose clinical features include excessive daytime sleepiness, hypnagogic hallucinations, cataplexy, sleep paralysis, and disrupted nocturnal sleep. It has been shown that there may be quite a long interval between the onset of symptoms, and the correct diagnosis. We tested the hypothesis that given their severe symptomatology, these patients would have been diagnosed more often with a variety of psychiatric and neurologic conditions than controls in the year prior to confirmation of their narcolepsy diagnosis. DESIGN: Using the Province of Manitoba Health database, we compared the diagnoses made in the year prior to initial sleep disorder center evaluation of 77 patients with narcolepsy (33 males, 44 females) and 1,155 matched control subjects from the general population. SETTING: Sleep disorders center in University-based teaching hospital PARTICIPANTS: N/A. INTERVENTIONS: N/A. MEASUREMENTS AND RESULTS: Patients were much more likely than controls to be diagnosed with mental disorders (Odds ratio (OR) = 4.0645; 95% confidence limit (CL) = 2.4671-6.6962; p<0.0001) and nervous system disorders (OR= 5.0495; CL = 3.0606 -8.3309; p<0.0001) and there was a trend towards more injuries in these patients (OR =1.6316; CL = 0.9857-2.7007; p=0.0514). We found that cases were statistically much more likely than controls to have received a diagnosis for neurotic disorders (17% of cases), depression (16%), personality disorders (3%) and adjustment reaction (4%). Although the cases had twice as many doctor visits as the controls (9.3 +/- 0.97 (sem) vs. 4.8 +/- 0.17 p<0.0001), only 38% of them had received a diagnosis of narcolepsy in the year prior to sleep specialist evaluation. Neurologists had the highest "success rate" for correct diagnosis: neurologists diagnosed narcolepsy in 55% of the cases they had seen. The other medical practitioners diagnosed narcolepsy in a much smaller percentage of the cases they had seen: 23.5% for internists (excluding neurologists), 21.9% for general practitioners, 11.1% for psychiatrists, and 0% for pediatricians. CONCLUSIONS: In the year prior to documentation of narcolepsy in a sleep disorders center, patients with narcolepsy were diagnosed with a wide variety of mental and neurologic disorders. Our findings are supportive of either the coexistence of these disorders in narcolepsy patients or a high frequency of missed diagnosis by their clinicians. The latter may help explain the very long interval between onset of symptoms and correct diagnosis.

Risk of physician-diagnosed asthma in the first 6 years of life.

OBJECTIVE: The objective of this cohort study was to determine if complications of pregnancy and labor, characteristics at birth, and exposure to infections influence the incidence of asthma in the first 6 years of life. DESIGN: We identified all children born between 1980 and 1990 in the Province of Manitoba, Canada. We used records of physician contacts (inpatient and outpatient) and services of the universal provincial health insurance plan to follow up 170,960 children from birth to the age of 6 years to identify the first diagnosis of asthma. Information on mothers and siblings was also obtained to determine family history of disease and exposure to infections. RESULTS: During the study period, a diagnosis of asthma was made in 14.1% of children by the age of 6 years. The incidence was higher in boys than in girls, in those with family history of allergic diseases. It was higher in urban than in rural areas, and lowest in those born in winter. Asthma was more likely in those with low birth weight and premature birth. Certain congenital abnormalities and complications of pregnancy and labor also increased the risk of asthma. The risk of asthma increased with maternal age. Both upper and lower respiratory infections increased the risk of subsequent asthma, and this effect was more important than exposure to familial respiratory infections, which also tended to increase asthma risk. The risk of asthma decreased with the number of siblings when siblings had a history of allergic disorders. CONCLUSIONS: In addition to genetic influences, intrauterine and labor conditions are determinants of asthma. Exposure to both upper and lower respiratory tract infections increases the risk; these infections do not explain the protective effect associated with the increasing number of siblings.

What are obstructive sleep apnea patients being treated for prior to this diagnosis?

BACKGROUND: Patients with obstructive sleep apnea syndrome (OSAS) use health-care resources at higher rates than control subjects for years prior to diagnosis. Although obesity and certain cardiovascular disorders are more common in OSAS patients, the precise cause of increased health-care utilization is unclear. OBJECTIVES: To examine the causes of increased utilization, and what patients with OSAS were being treated for prior to this diagnosis. METHODS: We compared the records of 773 patients with OSAS to those of age-, gender-, geographic-, and physician-matched control subjects from the general population. RESULTS: We found that sleep apnea patients used 23 to 50% more resources (defined by physician fees, physician visits, and hospital nights) in the 5 years prior to diagnosis than did control subjects. We examined the diagnoses made and found that apnea patients are at higher risk for hypertension (odds ratio [OR], 2.5; 95% confidence interval [CI], 2.0 to 3.3), congestive heart failure (OR, 3.9; 95% CI, 1.7 to 8.9), cardiac arrhythmias (OR, 2.2; 95% CI, 1.2 to 4.0), cardiovascular disease (OR, 2.6; 95% CI, 2.0 to 3.3), chronic obstructive airways disease (OR, 1.6; 95% CI, 1.2 to 2.0), and depression (OR, 1.4; 95% CI, 1.0 to 1.9). To control for the confounding effects of obesity and to determine the independent effects of body mass index (BMI), gender, age, degree of hypoxemia, apnea-hypopnea index, and sleepiness in the 773 patients, we performed a logistic regression analysis with the dependent variable being diagnosis, and a linear regression analysis with the dependent variable being measures of health-care utilization. Age and BMI were significant independent predictors of most cardiovascular diagnoses and arthropathy. Male gender predicted ischemic heart disease (OR, 2.98; 95% CI, 1.36 to 6.54), and female gender was predictive of chronic obstructive airways disease (OR, 2.63; 95% CI, 1.85 to 3.72) and depression (OR, 2.24; 95% CI, 1.45 to 3.44). The best model predicting health-care utilization measures was comprised of age, gender, and BMI, and explained 9%, 14%, and 8% of the variability in physician fees, number of physician claims, and number of physician visits, respectively. CONCLUSION: Of all comorbid diagnoses, significantly increased utilization was found for cardiovascular disease and especially hypertension in the OSAS patients.

Geographic and gender variability in the prevalence of bronchial responsiveness in Canada.

OBJECTIVES: Geographic variability in reported prevalences of asthma worldwide could in part relate to interpretation of symptoms and diagnostic biases. Bronchial responsiveness measurements provide objective evidence of a common physiologic characteristic of asthma. We measured bronchial responsiveness using the standardized protocol of the European Community Respiratory Health Survey (ECRHS) in six sites in Canada, and compared prevalences across Canada with international sites. DESIGN: Samples of 3,000 to 4,000 adults aged 20 to 44 years were randomly selected in Vancouver, Winnipeg, Hamilton, Montreal, Halifax, and Prince Edward Island, and a mail questionnaire was completed by 18,616 individuals (86.5%). Preselected random subsamples (n = 2,962) attended a research laboratory for examination including more detailed questionnaires, lung function testing including methacholine challenge, and skin testing with 14 allergens. RESULTS: Prevalences of bronchial hyperresponsiveness, measured as cumulative dose of methacholine required to produce a 20% fall from the post-saline solution FEV1 < or = 1 mg, ranged from 4.9% (95% confidence interval [CI], 1.6 to 8.5) in Halifax to 22.0% (95% CI, 18.1 to 26.0) in Hamilton (median, 10.7%). In all Canadian sites, bronchial hyperresponsiveness was more prevalent in women than in men. Neither the geographic nor gender differences were accounted for by differences in age, smoking, skin test reactivity, or baseline FEV1. Geographic- and gender-related variability changed little when only bronchial hyperresponsiveness associated with asthma-like symptoms was considered. CONCLUSIONS: A wide variability in bronchial responsiveness can occur within one country, almost as wide as the range found across all international sites participating in the ECRHS study and not explained by differences in gender, smoking, skin test reactivity, and FEV1. While gender variability in the prevalence of bronchial responsiveness is likely due to hormonal and immunologic factors, geographic variability is likely to result from environmental factors.

Tuberculous lymphadenitis in Manitoba: incidence, clinical characteristics and treatment.

BACKGROUND: Tuberculous lymphadenitis (TBL) is an important form of extrapulmonary tuberculosis (TB). Recent studies have shown an increase in TBL in Canada. OBJECTIVES: To determine the incidence of TBL in Manitoba and to identify the characteristics associated with its presentation, diagnosis and treatment METHODS: Population data from the Manitoba Health Population Registry, the First Nations and Inuit Health Branch of Health Canada, and Statistics Canada were used to calculate incidence. Case characteristics and outcomes were determined by a systematic, retrospective review of all cases between January 1, 1990 and December 31, 2000. RESULTS: One-hundred forty seven cases of TBL were identified during the study period; 77% confirmed by culture; 68% women. TBL was found in Canadian-born/nonstatus Aboriginal (12%), status Aboriginal (29%) and foreign-born (59%) populations. Incidence of TBL was 1.17 per 100,000 person years (95% CI 0.98 to 1.36). The highest incidence was in status Aboriginals over 65 years (16.85 per 100,000 person years; 95% CI 3.37 to 30.33). TBL is seen most often in Western Pacific women. The most common presentation was a single, enlarged cervical node (80%). No atypical mycobacterium was found. Drug resistance occurred in 13% of cases and only in the foreign-born. Cure rates (81%) were influenced by comorbidity and burden of TB disease. Relapse occurred in 8.1 per 1000 person years of follow-up (95% CI 1.7 to 23.7). CONCLUSIONS: Respiratory physicians, who manage the majority of TB disease in Canada, need to remain aware that TB is an important and treatable cause of enlarged lymph nodes.

Diagnosing asthma: the fit between survey and administrative database.

BACKGROUND: Standard methods for population studies of asthma include surveying population samples using questionnaires and examining people in laboratories. These procedures are extremely expensive. It would be helpful if, at least for some purposes, they could be replaced by cheaper techniques with adequate validity. OBJECTIVES: To determine agreement between survey and database in regard to the prevalence of asthma. METHODS: Responses to survey questions about asthma symptoms in the past 12 months were linked to physician claims in the Manitoba Population Health Repository. RESULTS: The overall agreement was moderate (k=0.45 to 0.50) and increased if two years of physician claims were studied (k=0.55 to 0.59); studying additional years had no further effect on agreement. Sex and smoking did not significantly affect the kappa scores. CONCLUSIONS: There were several plausible reasons for discrepancies. Symptoms recorded on the survey were intrinsically different from those recorded for physician visits. Physicians also used other respiratory codes instead of asthma, and survey participants did not see a physician every year for asthma. The estimates of prevalence derived from the survey and the administrative database included two overlapping groups of people. In each, the diagnosis of asthma seems justifiable, although the agreement between the two groups was only moderate to substantial. Both methods are useful, although they are useful for different purposes. Health care utilization estimates may be particularly useful for studying trends over time.