Biomedical subjects

J Manfreda

Publications and source records attributed to J Manfreda.

At least 37 records · Page 2Linked to original sources

PubMed1999

Upper airway resistance syndrome: effect of nasal dilation, sleep stage, and sleep position.

BACKGROUND: The upper airway resistance syndrome (UARS) is one of the mild variants of obstructive sleep disordered breathing. Nasal obstruction is proposed as one of the mechanisms that lowers intrapharyngeal pressure and hence increases airway collapsibility. OBJECTIVE: We evaluated the effect of external nasal dilation and sleep position on sleep in UARS. METHOD: A double blind, randomized, controlled study with a crossover design (using therapeutic and placebo dilators) was conducted in 18 consecutive patients with UARS. Each patient had two overnight sleep studies one to two weeks apart. Cardiorespiratory parameters (AHI, percentage of time that SaO2 was more than 2% below awake [desaturation time] and mean overnight heart rate), sleep architecture (sleep stages, sleep efficiency, and arousal index), and body position were determined. RESULTS: Application of the external nasal dilator resulted in a significant increase in the nasal cross-sectional area (p < 0.001). Treatment reduced stage 1 sleep (as a percent of total sleep time) from 8.6 +/- 0.8% to 7.1 +/- 0.7 (SEM), p = 0.034). Desaturation time was significantly lower with treatment (12.2 +/- 2.2% on placebo versus 9.1 +/- 1.3 on treatment, p = 0.04). There were no additional significant effects on the cardiorespiratory parameters, sleep architecture, or MSLT when the entire night was examined. Controlling for interactions of sleep stage and position and treatment we found that treatment reduced desaturation time (p = 0.03) but not AHI or arousal index. AHI was significantly lower in the lateral position compared to the supine (p = 0.0001) and in NREM sleep compared to REM (p = 0.001). Desaturation time was significantly lower on the lateral compared to the supine position (p = 0.002) and in NREM sleep compared to REM (p = 0.006). Arousal index was highly dependent on sleep stage (p = 0.0001): the index was higher in stage 2 compared to slow wave sleep and REM. Sleep position and treatment had no significant effect on arousals. CONCLUSIONS: External nasal dilation reduced stage 1 sleep, an indirect marker of disrupted sleep, and desaturation time. There were no additional effects on sleep architecture or sleep disordered breathing. Both sleep position and sleep stage had a significant effect on sleep disordered breathing in UARS.

Airway Resistance↗

PubMed1999

Health care utilization in the 10 years prior to diagnosis in obstructive sleep apnea syndrome patients.

Obstructive sleep apnea syndrome (OSAS) patients may have symptoms for years prior to recognition of their disorder, or they may be treated for the associated comorbidities. We hypothesized that such patients would be heavy consumers of health care resources for several years prior to diagnosis. We therefore compared health service utilization for a 10-year interval prior to diagnosis of 181 OSA patients to those of randomly selected age-, gender-, and geographically matched controls from the general population. OSAS patients used approximately twice as many health care services (as defined by physician claims and overnight stays in hospital) in the 10 years prior to their initial diagnostic evaluation for apnea. Physician claims for the OSA patients totaled $686,365 ($3972 per patient), compared to $356,376 ($1969 per patient) for the controls for the 10-year period examined in this study. Use of health services was significantly higher in 7 of 10 years prior to diagnosis. The OSAS patients also had more overnight hospitalizations: they spent 1118 nights (6.2 per patient) in hospital vs 676 nights (3.7 per patient) for controls in the decade prior to diagnosis. We conclude that by the time patients are finally diagnosed for sleep apnea, they have already been heavy users of health services for several years. It is possible that our findings reflect not OSAS per se, but the presence of some of the risk factors that predispose to OSAS, such as obesity, alcohol usage and perhaps tobacco consumption.

Canada↗

PubMed1999

Breast-feeding and environmental tobacco smoke exposure.

BACKGROUND: Exposure to environmental tobacco smoke is associated with adverse effects in infants and children. OBJECTIVE: To explore whether an increase in urinary cotinine fumarate level is caused by ingested nicotine and cotinine in breast-feeding infants. METHODS: We studied newborns at risk for developing asthma and allergies based on a strong family history. We measured urinary cotinine levels in the infants as a measure of environmental tobacco smoke exposure and cotinine levels in the breast milk of breast-feeding mothers. RESULTS: Of 507 infants, urinary cotinine levels during the first 2 weeks of life were significantly increased in infants whose mothers smoked. Breast-fed infants had higher cotinine levels than non-breast-fed infants, but this was statistically significant (P<.05) only if mothers smoked. Urinary cotinine levels were 5 times higher in breast-fed infants whose mothers smoked than in those whose mothers smoked but did not breast-feed. CONCLUSIONS: Mothers should be encouraged to not smoke, and parents must be advised of the potential respiratory and systemic risks of environmental tobacco smoke exposure to their child, including the potential for future addiction to smoking.

Breast Feeding↗

PubMed1999

Umbilical cord blood mononuclear cell proliferative response to house dust mite does not predict the development of allergic rhinitis and asthma.

BACKGROUND: Cord blood mononuclear cells (CBMNCs) have been found to proliferate when stimulated with food or inhalant allergens. The significance of this finding is not known. OBJECTIVES: We sought to determine the factors associated with proliferation of CBMNCs when stimulated with house dust mite (HDM) allergen and to determine whether proliferation of CBMNCs is associated with subsequent development of HDM sensitization and development of allergic rhinitis and asthma. METHODS: Cord blood was taken from infants at high risk for having asthma and allergic diseases who were recruited for a primary prevention study in which infants were randomized into the intervention or the control group. CBMNCs were stimulated with HDM allergen and PHA as a positive control. Infants were assessed at 12 and 24 months for health outcome. RESULTS: When stimulated with HDM allergen, 29.7% of infants had a stimulation index (SI) of 2 or greater. There were no differences in the levels of cord blood IgE and cotinine, maternal smoking, immediate skin test reactivity, maternal IgE, and maternal exposure to HDM allergen between those with an SI of 2 or greater and those with an SI of less than 2. Infants with an SI of less than 2 had a significantly higher proportion of mothers with a history of asthma. No differences in the incidence of "asthma" and rhinitis without cold at 12 months and cumulative prevalence at 24 months were seen between the 2 groups. None of the infants had skin test reactions to HDM allergen. CONCLUSION: The negative association between HDM allergen-induced proliferation of CBMNCs and maternal mite allergen exposure and health outcomes at 12 and 24 months raises the issue of the significance of CBMNC proliferation.

Allergens↗

PubMed1999

Exposure and sensitization to cat dander: asthma and asthma-like symptoms among adults.

BACKGROUND: Several pets, such as cats, dogs, and rodents, are known to produce allergens. Despite the clinical and laboratory evidence that exposure to pets can cause bronchoconstriction in sensitized subjects, the results of population studies have been contradictory. OBJECTIVES: The purpose of this study was to investigate the relationship between cat ownership and the prevalence of asthma, asthma-like symptoms, and bronchitic symptoms among subjects 20 to 44 years of age in Vancouver, Canada and to determine whether sensitization is responsible for such an association. METHODS: Two thousand nine hundred ninety-nine (88%) randomly selected subjects responded to a mail questionnaire. Of these, 504 participated in laboratory examination, including allergy skin testing. RESULTS: One thousand nineteen study responders (34%) were pet owners at the time of the study (current owners). Current pet owners were found to have a higher prevalence of current asthma, asthma-like symptoms, and bronchitic symptoms compared with those without pets. Cat owners had significantly higher risk of having current asthma and asthma-like symptoms. In the subset who had allergic skin tests, we found that those who were allergic to cat dander had a significantly higher risk of current asthma than those not allergic to cat dander and not owning a cat. CONCLUSION: This study provides evidence that sensitization to cat dander is a more important risk factor for current asthma and asthma-like symptoms than cat ownership itself.

Adult↗

PubMed1998

The effect of age on risk factors for ischemic heart disease: the Manitoba Follow-Up Study, 1948-1993.

PURPOSE: The purpose of this paper is to determine the age-specific relationships between risk factors at age 40 through 75 years and ischemic heart disease (IHD), and to determine the effects of aging on these relationships in a cohort of 3983 Canadian males. METHODS: The Manitoba Follow-Up Study is the prospective investigation of cardiovascular disease as it develops in a cohort of 3983 young men. Over a period of 45 years, from 1948 to 1993, 1094 study members (27%) developed clinical evidence of IHD. Blood pressure, body weight, smoking, and presence of diabetes mellitus have been recorded at regular intervals throughout the follow-up period. Using measurements from examinations every 5 years between ages 40 and 75 years, age-specific Cox proportional hazard models were fit to relate these risk factors to IHD. RESULTS: The adjusted relative risk of IHD for systolic blood pressure, diastolic blood pressure and smoking were found to significantly (p < 0.001) decline with advancing age. The adjusted relative risk for body mass index and presence of diabetes mellitus for ischemic heart disease did not vary with age (p > 0.05). After age 65 years, these risk factors were of little value for the prediction of IHD. CONCLUSIONS: The relative risk and statistical significance of blood pressure and smoking, as risk factors for IHD, decline with age.

Adult↗

PubMed1998

M. tuberculosis molecular variation in CNS infection: evidence for strain-dependent neurovirulence.

OBJECTIVE: To determine the molecular diversity among Mycobacterium tuberculosis isolates associated with central nervous system tuberculosis (CNS TB) in a defined cohort of HIV uninfected patients. DESIGN/METHODS: A retrospective analysis was performed of clinical and laboratory data for all patients with CNS TB diagnosed in Manitoba, Canada, between 1979 and 1996. Restriction fragment-length polymorphisms (RFLP) of archival isolates of M. tuberculosis from CNS TB patients were determined and interpreted against the frequency of different isolates from all TB patients in the years 1992 to 1996. RESULTS: Among 2,334 patients with active TB, CNS TB was diagnosed in 42 (1.8%); meningitis with or without tuberculoma in 76%; and tuberculoma alone in 24%. CNS TB patients were significantly more likely to be young (<40 years old), female, and of Aboriginal origin. Morbidity (fixed/recurrent CNS deficit) rate was 29% and mortality rate was 26%. An adverse outcome, either morbidity or mortality, was significantly more common in those with meningitis. RFLP analysis of isolates (n=19) from CNS TB patients revealed 13 distinct restriction patterns with a predominance of the type 1 pattern (n=6). The frequency of type 1 restriction pattern was significantly greater in patients with CNS TB compared to all TB patients in Manitoba. CONCLUSIONS: CNS TB continues to have a high morbidity and mortality despite modern methods of detection and treatment. Although several strains of M. tuberculosis cause CNS TB, the current study suggests that the occurrence of CNS TB may be strain-dependent.

Adult↗

PubMed1998

Respiratory symptoms in a susceptible population due to burning of agricultural residue.

STUDY OBJECTIVES: To identify characteristics associated with respiratory symptoms due to an episode of air pollution. DESIGN: Mail survey. SETTING: In October 1992, the population of the city of Winnipeg was exposed to elevated levels of particulate matter (total and <10 microm size), carbon monoxide, nitrogen dioxide, and volatile organic compounds due to smoke from adjacent fields where farmers were burning agricultural residue (straw and stubble). PARTICIPANTS: We surveyed 428 participants in the ongoing Lung Health Study (35 to 64 years old, both sexes) with mild to moderate airways obstruction (mean FEV1 percent predicted 73+/-12%), and a high level of airways hyperreactivity (23% of men and 37% of women). RESULTS: While 37% of subjects were not bothered by smoke at all, 42% reported that symptoms (cough, wheezing, chest tightness, shortness of breath) developed or became worse due to the air pollution episode and 20% reported that they had breathing trouble. Those with symptoms were more likely to be female than male and were more likely to be ex-smokers than smokers. Subjects with asthma and chronic bronchitis were also more likely affected. The degree of airways obstruction and the level of bronchial hyperresponsiveness were not associated with increased susceptibility. CONCLUSIONS: Gender, smoking habit, and respiratory symptoms but not bronchial hyperresponsiveness or the degree of airways obstruction are factors influencing susceptibility to symptoms due to air pollution in adult smokers and former smokers.

Adult↗

PubMed1998

Pulmonary tuberculosis treated with directly observed therapy: serial changes in lung structure and function.

OBJECTIVES: (1) To correlate structure (CT) with function in pulmonary tuberculosis (TB), and (2) to describe the evolution of structural and functional abnormalities when pulmonary TB is treated with directly observed therapy. SUBJECTS AND METHODS: Twenty-five patients with drug-susceptible pulmonary TB, 15 cavitary and 10 noncavitary, were studied prospectively. Conventional CT and pulmonary function testing (spirometry, diffusing capacity, and arterial blood gases) were performed at baseline, and after 1 and 6 months of directly observed therapy. RESULTS: All but one patient with noncavitary miliary TB had CT evidence of endobronchial disease, and all patients with cavitary disease had coexistent reduced lung attenuation, the latter presumably a result of gas trapping, hypoxic vasoconstriction, and vascular injury. Functional impairment was minimal and in proportion to the number of diseased segments and cavitary volume. Bronchiectasis was significantly more likely to complicate cavitary than noncavitary disease (64 vs 11%; p<0.05). CONCLUSIONS: CT findings correlate well with function in pulmonary TB. Physiologic data were consistent with the concept that pulmonary TB is an endobronchial disease that causes parallel reductions in ventilation and perfusion. This concurrent involvement of both airways and contiguous pulmonary blood supply offers an explanation for the minimal respiratory limitation experienced by these patients despite often extensive lung disease. Supervised therapy of drug-susceptible disease results in minimal structural and functional residua.

Adult↗

PubMed1997

Income level and asthma prevalence and care patterns.

Manitoba has a universally accessible health-care system that records physician contacts and hospitalizations in such a way that they can be ascribed to individuals. We examined the prevalence of physician-diagnosed asthma, bronchitis, and airways obstruction (total respiratory morbidity [TRM]) in Winnipeg in 1988 and 1992, using place of residence to divide people into quintiles according to average family income. Physician office visits, hospitalizations, and consultation referrals were each examined. Three age groups: 0 to 14 yr, 15 to 34 yr, and > or = 35 yr were studied. The prevalence of TRM was greater in low- than in high-income quintiles. Asthma prevalence was unrelated to income in the younger age groups; in the older group asthma was more common in low-income groups, but was less strongly related to income than was TRM. Asthma prevalence increased over the years studied, but the increase was not related to income level. There was some evidence of income-related diagnostic bias in that low-income patients were more likely to be labeled with a related diagnosis in addition to asthma than were high-income patients. Low-income patients had more physician contacts than did high-income patients. In terms of physician office visits, care continuity did not differ among income quintiles. Low-income quintiles had more hospitalizations than did high-income quintiles, and differences were larger than could be accounted for by diagnostic bias; asthma was probably more severe in low-income quintiles. High-income quintiles had more consultation referrals than did low-income quintiles.

Adolescent↗

PubMed1997

Disseminated tuberculosis with and without a miliary pattern on chest radiograph: a clinical-pathologic-radiologic correlation.

SETTING: Province of Manitoba, Canada. OBJECTIVE: To describe the characteristics of disseminated tuberculosis (TBD) with and without a miliary pattern on chest radiograph, to determine the mortality, and to identify the demographic and clinical features associated with survival. DESIGN: A retrospective case review. RESULTS: Of 2013 cases of active tuberculosis reported to the Provincial Tuberculosis Registry between January 1979 and December 1993, 56 had disseminated disease. The odds of developing TBD were significantly higher in females. Compared to those with a miliary pattern (n = 42), those without a miliary pattern on chest radiograph (n = 14) were significantly more likely to have a risk factor for tuberculosis (86% vs 52%, P < 0.05) and to die (86% vs 21%, P < 0.001). The diagnosis of TBD was significantly more likely to be made at postmortem in non-miliary compared to miliary patients (43% vs 5%, P < 0.05). Amongst patients with a miliary pattern, the presence of one or more risk factors for tuberculosis was associated with a significantly higher mortality (P < 0.05). Meningitis was very uncommon and did not determine the outcome. CONCLUSION: Disseminated tuberculosis patients without a miliary pattern on chest radiograph have an extremely high mortality rate; those with a miliary pattern may also succumb, especially if co-morbid with a condition known to increase the risk of tuberculosis.

Adult↗

PubMed1996

Effect of application of benzyl benzoate on house dust mite allergen levels.

BACKGROUND: Several acaricides have become available for reducing house dust mite allergen levels. OBJECTIVE: The purpose of this study was to assess whether the use of benzyl benzoate (Acarosan) provides additional benefit to the usual mite control measures including encasement of mattress and pillows with vinyl covers. METHODS: A randomized controlled trial was carried out in 26 homes (14 control versus 12 treatment) of asthmatic patients in two cities (Vancouver and Winnipeg). The control group had the usual house dust mite control measures including the use of vinyl covers for mattresses and pillows while the treatment group had application of benzyl benzoate to mattresses and carpets in the bedroom and the most commonly used room, in addition to the above control measures. Mite allergen levels were measured 3 months and immediately before, 1 week, and 1 and 3 months after the application of house dust mite control measures. Patients kept diary cards on asthma symptoms and peak expiratory flow rates morning and evening one month before and three months after the onset of mite allergen control measures. RESULTS: A reduction of mite allergen level was found in mattress samples in both groups, statistically significant at all times in the treatment group and at one and three months in the control group. Mite allergen levels on floor carpets also showed progressive reduction in both groups, but were significantly different in the treatment group (compared with controls) at 1 week, and were lower compared with baseline in the treatment group up to 3 months. No significant changes in asthma symptoms, peak expiratory flow rates, spirometric measurements, or bronchial hyperresponsiveness were observed among treatment or control group subjects. CONCLUSION: The addition of benzyl benzoate to conventional house dust mite control measures resulted in a significant reduction in floor carpet dust mite levels that persisted for 3 months. The results of this study should be confirmed in a larger and longer study.

Adult↗

PubMed1996

Changes in peak flow, symptom score, and the use of medications during acute exacerbations of asthma.

Changes in symptom score and peak expiratory flow (PEF) and the use of medications during the first acute exacerbation of asthma were studied in 41 patients and matched controls who took part in a panel study. An acute exacerbation was defined as the presence of at least one of the following: any unscheduled physician visit, visit to an emergency room, or hospitalization for treatment of asthma; a decrease in PEF by 30% from the patient's best reading; an increase in asthma symptoms during the day and night for over 48 h and not responding to usual medications; and the commencement or doubling of the dose of oral or inhaled steroids for any of the foregoing reasons. Data from -9 to -7 d before the onset of an acute exacerbation were taken as the baseline data, with which the values of the subsequent 14 d were compared. Significant increases in symptoms occurred before a significant reduction in PEF. None of the patients had a decrease of more than 30% in PEF before the onset of symptoms. Daily variation in PEF was not significantly increased from the baseline. Our results suggest that PEF monitoring is not as sensitive as a symptom diary for revealing acute exacerbations of asthma, and that a 30% decrease in PEF is too stringent a criterion for defining an acute exacerbation.

Acute Disease↗

PubMed1996

Risk of preschool asthma: incidence, hospitalization, recurrence, and readmission probability.

Asthma is one of the most common chronic illnesses in childhood. Increases in hospitalization rates have occurred in several countries. The cumulative risk of asthma requiring medical attention was 11.7% for males and 7.0% for females aged 0-4 in Manitoba, Canada, for the cohort of children born in 1984/1985. The cumulative risk of hospitalization for males was nearly twice that of females (2.1% vs. 1.1%). Disease onset was most likely at age 1 year. The risk of rehospitalization or return physician visit for asthma increased significantly with the number of prior hospitalizations and physician visits, respectively, which may reflect both the persistence of asthma and the difficulty of developing an effective disease management strategy.

Age of Onset↗

PubMed1995

Tracking of blood pressure over a 40-year period in the University of Manitoba Follow-up Study, 1948-1988.

High blood pressure is a well-recognized, modifiable, cardiovascular disease risk factor. Tracking of blood pressure was examined in the University of Manitoba Follow-up Study, a cohort of 3,983 men followed over a 40-year period, between 1948 and 1988. Blood pressure measurements recorded over time in these men, prior to the development of ischemic heart disease, were used in this analysis. Two approaches to tracking were used; correlation analysis and the quantification of the likelihood for a man whose blood pressure was in either the top or bottom quintile to remain in the extreme end of the distribution at later measurement. For ages 25-75 years and for intervals between blood pressure measurement ranging from 5 to 35 years, significant evidence for tracking was found. The strongest evidence for tracking was in middle age, 45-55 years. Strength of tracking decreased with increasing time between measurements. This analysis suggests that men at highest risk for hypertension can be identified at a young age. Hence, strategies for prevention of cardiovascular complications can be targeted in early adulthood.

Adult↗

PubMed1995

The natural history of atrial fibrillation: incidence, risk factors, and prognosis in the Manitoba Follow-Up Study.

PURPOSE: Atrial fibrillation is a common arrhythmia associated with increased cardiovascular morbidity and mortality. This study was undertaken to identify the natural history of this condition, including risk factors for its development, and outcome. PATIENTS AND METHODS: The incidence of atrial fibrillation among 3,983 male air crew recruits observed continuously for 44 years was calculated based on person-years of observation. Age and 23 variables were examined to identify risk factors for atrial fibrillation. Controlling for age and 9 prognostic variables, the effect of atrial fibrillation on 8 outcomes was examined. Analysis of risk factors for atrial fibrillation and outcome after atrial fibrillation was based on a Cox proportional hazard model using time-dependent covariates. RESULTS: Of the 3,983 study members, 299 (7.5%) developed atrial fibrillation during 154,131 person-years of observation. The incidence rose with age from less than 0.5 per 1,000 person-years before age 50 to 9.7 per 1,000 person-years after age 70. Risk for atrial fibrillation was increased with myocardial infarction (relative risk [RR] 3.62), angina (RR 2.84), and ST-T wave abnormalities in the absence of ischemic heart disease (RR 2.21). The RR for atrial fibrillation was strongest at the onset of ischemic heart disease and diminished over time. The rate of atrial fibrillation was 1.42 times increased in men with a history of hypertension. Congestive heart failure, valvular heart disease, and cardiomyopathy were important but uncommon risk factors. Atrial fibrillation independently increased the risk for stroke (RR 2.07) and congestive heart failure (RR 2.98). Total mortality rate was increased 1.31 times; cardiovascular mortality including and excluding fatal stroke were also increased (RR 1.41 and 1.37, respectively). CONCLUSIONS: The incidence of atrial fibrillation in men increases with advancing age. Clinical cardiac abnormalities, particularly recent ischemic heart disease and hypertension, are strongly associated with increased risk for atrial fibrillation. Atrial fibrillation increases morbidity and mortality, but the magnitude of the increase may be less than previously reported.

Adult↗

PubMed1995

Clinical significance of nontuberculous mycobacteria isolates in a Canadian tertiary care center.

To determine the epidemiology and clinical features of disease due to nontuberculous mycobacteria (NTM) in our institution, we reviewed the medical records of all patients from whom NTM isolates were recovered from 1988 to 1990 to extract selected clinical and laboratory data. On the basis of the likelihood of infection, patients were classified as having definite, probable, or unlikely NTM disease as defined by published guidelines. Of 80 patients who met the inclusion criteria, 17 had definite NTM disease, and 23 had probable NTM disease. No differences in age, sex, presence of underlying pulmonary or nonpulmonary disease, or chest radiographic abnormalities were noted between patients with and without NTM disease. More than 85% of all definite or probable cases were caused by Mycobacterium avium complex, Mycobacterium kansasii, and Mycobacterium fortuitum complex. The diagnosis of NTM disease was often delayed or missed, which resulted in unsatisfactory management of patients. There is a need to educate physicians about the diagnosis and management of NTM infections.

Academic Medical Centers↗

PubMed1995

House dust mite allergen levels in two cities in Canada: effects of season, humidity, city and home characteristics.

The homes of 120 patients with asthma, 57 in Vancouver and 63 in Winnipeg, were studied. The characteristics of the homes were assessed by a questionnaire. Dust samples were collected and the indoor relative humidity was measured four times during the year covering all four seasons in both cities. Mite allergen levels were determined using monoclonal antibodies against Der p I and Der f I by the ELISA method. The mean levels of both mite allergens in mattress and floor samples in the homes in Vancouver and in Winnipeg were relatively low for all seasons. Mite allergen levels were found to be associated with city, season and individual home differences. They were significantly higher in Vancouver than in Winnipeg. Der p I and Der f I in mattress samples in both cities and Der f I in floor samples in Vancouver, varied by season. The indoor relative humidity level in the homes in Vancouver were also significantly higher than those in Winnipeg. There was, however, no significant association between the levels of indoor relative humidity and the levels of mite allergens after adjusting for variations in city, season and individual home. Although individual home differences were highly associated with mite allergen levels, only a few home characteristics were found to be related to mite allergen levels such as the type and the age of the home, the type of heating, the use of feather pillows and the number of occupants in the homes. Whether low levels of mite allergens are partially responsible for the relatively low prevalence of childhood asthma in Canada remains to be investigated.

Allergens↗