Etiology and pathogenesis of airway disease in children and adults from rural communities

Regional PM2.5 and asthma morbidity in an agricultural community: a panel study

BACKGROUND

Elevated pediatric asthma morbidity has been observed in rural US communities, but the role of the ambient environment in exacerbating rural asthma is poorly understood.

OBJECTIVES

To investigate associations between particulate matter less than 2.5 μm in diameter (PM2.5) and pediatric asthma exacerbations in an agricultural community of Washington State.

METHODS

School-aged children with asthma (n=58) were followed for up to 25 months with repeated measures of respiratory health. Asthma symptoms and quick-relief medication use were assessed biweekly through phone administered surveys (n=2023 interviews). In addition, subjects used home peak flow meters on a daily basis to measure forced expiratory volume in one second (FEV1) (n=7830 measurements). Regional PM2.5 was measured at a single air monitor located centrally in the study region. To assess relationships between PM2.5 and these outcomes we used linear regression with generalized estimating equations, adjusting for meteorological and temporal confounders. Effect modification by atopy was explored as well.

RESULTS

An interquartile increase (IQR) in weekly PM2.5 of 6.7 μg/m(3) was associated with an increase in reported asthma symptoms Specific symptoms including wheezing, limitation of activities, and nighttime waking displayed the strongest associations. FEV1 as a percent of predicted decreased by 0.9% (95%CI: -1.8, 0.0) for an IQR increase in PM2.5 one day prior, and by 1.4% (95%CI: -2.7, -0.2) when restricted to children with atopic asthma.

CONCLUSIONS

This study provides evidence that PM2.5 in an agricultural setting contributes to elevated asthma morbidity. Further work on identifying and mitigating sources of PM2.5 in the area is warranted.

Phospholipase A(2) activation by poultry particulate matter is mediated through extracellular signal-regulated kinase in lung epithelial cells: regulation of interleukin-8 release

The mechanisms of poultry particulate matter (PM)-induced agricultural respiratory disorders are not thoroughly understood. Hence, it is hypothesized in this article that poultry PM induces the release of interleukin-8 (IL-8) by lung epithelial cells that is regulated upstream by the concerted action of cytosolic phospholipase A2 (cPLA2) and extracellular signal-regulated kinase (ERK). To test this hypothesis, the widely used cultured human lung epithelial cells (A549) were chosen as the model system. Poultry PM caused a significant activation of PLA2 in A549 cells, which was attenuated by AACOCF3 (cPLA2 inhibitor) and PD98059 (ERK-1/2 upstream inhibitor). Poultry PM induced upstream ERK-1/2 phosphorylation and downstream cPLA2 serine phosphorylation, in a concerted fashion, in cells with enhanced association of ERK-1/2 and cPLA2. The poultry PM-induced cPLA2 serine phosphorylation and IL-8 release were attenuated by AACOCF3, PD98059, and by transfection with dominant-negative ERK-1/2 DNA in cells. The poultry PM-induced IL-8 release by the bone marrow-derived macrophages of cPLA2 knockout mice was significantly lower. For the first time, this study demonstrated that the poultry PM-induced IL-8 secretion by human lung epithelial cells was regulated by cPLA2 activation through ERK-mediated serine phosphorylation, suggesting a mechanism of airway inflammation among poultry farm workers.

Indoor and outdoor particulate matter and endotoxin concentrations in an intensely agricultural county

The objectives of this study were to characterize rural populations' indoor and outdoor exposure to particulate matter (PM)(10), PM(2.5), and endotoxin and identify factors that influence these concentrations. Samples were collected at 197 rural households over five continuous days between 2007 and 2011. Geometric mean (GM) indoor PM(10) (21.2 μg/m(3)) and PM(2.5) (12.2 μg/m(3)) concentrations tended to be larger than outdoor PM(10) (19.6 μg/m(3)) and PM(2.5) (8.2 μg/m(3)) concentrations (PM(10) P=0.086; PM(2.5) P<0.001). Conversely, GM outdoor endotoxin concentrations (1.93 EU/m(-3)) were significantly larger than indoor (0.32 EU/m(3); P<0.001). Compared with measurements from previous urban studies, indoor and outdoor concentrations of PM(10) and PM(2.5) in the study area tended to be smaller, whereas ambient endotoxin concentrations measured outside rural households were 3-10 times larger. Contrary to our initial hypothesis, seasonality did not have a significant effect on mean ambient PM(10) concentrations; however, endotoxin concentrations in the autumn were almost seven times larger than winter. Excluding home cleanliness, the majority of agricultural and housing characteristics evaluated were found to be poorly associated with indoor and outdoor particulate and endotoxin concentrations.

Regulating the Regulators: microRNA and Asthma

One obstacle to developing an effective therapeutic strategy to treat or prevent asthma is that the fundamental causes of asthma are not totally understood. Asthma is thought to be a chronic T_H2 immune-mediated inflammatory disease. Epigenetic changes are recognized to play a role in the initiation and maintenance of a T_H2 response. MicroRNAs (miRNAs) are key epigenetic regulators of gene expression, and their expression is highly regulated, therefore, deregulation of miRNAs may play an important role in the pathogenesis of asthma. Profiling circulating miRNA might provide the highest specificity and sensitivity to diagnose asthma; similarly, correcting potential defects in the miRNA regulation network may lead to new therapeutic modalities to treat this disease.

Birth outcomes across three rural-urban typologies in the Finger Lakes region of New York

PURPOSE

The study is a descriptive, population-based analysis of birth outcomes in the New York State Finger Lakes region designed to determine whether perinatal outcomes differed across 3 rural typologies.

METHODS

Hospital birth data for the Finger Lakes region from 2006 to 2007 were used to identify births classified as low birthweight (LBW), small for gestational age (SGA), and preterm delivery (PTD). Maternal residences were defined using 3 existing ZIP code-level rural-urban typologies: Census Bureau ZIP codes, Rural-Urban Commuting Area codes, and Primary Service Areas. Within each typology, rural maternal characteristics and birth outcomes were compared to those in urban areas using multivariable logistic regression models.

FINDINGS

In bivariate analyses, rurality was associated with LBW and SGA for all typologies, whereas PTD was associated with residence in the Census Bureau typology only. After controlling for demographic characteristics, births to mothers in the most rural level of the Census Bureau typology and to all rural mothers in the Rural-Urban Commuting Area (RUCA) and Primary Service Area typologies were more likely to be LBW and PTD. SGA was not consistently associated with residence across typologies.

CONCLUSIONS

The typologies produced similar results for these outcomes, although effects were of greater magnitude in the RUCA and Primary Service Area typologies than in the Census Bureau typology. Comparison across typologies can have practical implications for researchers and policy makers interested in understanding the dynamics of rurality and birth outcomes in their regions.

Airborne cow allergen, ammonia and particulate matter at homes vary with distance to industrial scale dairy operations: an exposure assessment

BACKGROUND

Community exposures to environmental contaminants from industrial scale dairy operations are poorly understood. The purpose of this study was to evaluate the impact of dairy operations on nearby communities by assessing airborne contaminants (particulate matter, ammonia, and cow allergen, Bos d 2) associated with dairy operations inside and outside homes.

METHODS

The study was conducted in 40 homes in the Yakima Valley, Washington State where over 61 dairies operate.

RESULTS

A concentration gradient was observed showing that airborne contaminants are significantly greater at homes within one-quarter mile (0.4 km) of dairy facilities, outdoor Bos d 2, ammonia, and TD were 60, eight, and two times higher as compared to homes greater than three miles (4.8 km) away. In addition median indoor airborne Bos d 2 and ammonia concentrations were approximately 10 and two times higher in homes within one-quarter mile (0.4 km) compared to homes greater than three miles (4.8 km) away.

CONCLUSIONS

These findings demonstrate that dairy operations increase community exposures to agents with known human health effects. This study also provides evidence that airborne biological contaminants (i.e. cow allergen) associated with airborne particulate matter are statistically elevated at distances up to three miles (4.8 km) from dairy operations.

Antigen sensitization influences organophosphorus pesticide-induced airway hyperreactivity

BACKGROUND

Recent epidemiologic studies have identified organophosphorus pesticides (OPs) as environmental factors potentially contributing to the increase in asthma prevalence over the last 25 years. In support of this hypothesis, we have demonstrated that environmentally relevant concentrations of OPs induce airway hyperreactivity in guinea pigs.

OBJECTIVES

Sensitization to allergen is a significant contributing factor in asthma, and we have shown that sensitization changes virus-induced airway hyperreactivity from an eosinophil-independent mechanism to one mediated by eosinophils. Here, we determine whether sensitization similarly influences OP-induced airway hyperreactivity.

METHODS

Nonsensitized and ovalbumin-sensitized guinea pigs were injected subcutaneously with the OP parathion (0.001-1.0 mg/kg). Twenty-four hours later, animals were anesthetized and ventilated, and bronchoconstriction was measured in response to either vagal stimulation or intravenous acetylcholine. Inflammatory cells and acetylcholinesterase activity were assessed in tissues collected immediately after physiologic measurements.

RESULTS

Ovalbumin sensitization decreased the threshold dose for parathion-induced airway hyperreactivity and exacerbated parathion effects on vagally induced bronchoconstriction. Pretreatment with antibody to interleukin (IL)-5 prevented parathion-induced hyperreactivity in sensitized but not in nonsensitized guinea pigs. Parathion did not increase the number of eosinophils in airways or the number of eosinophils associated with airway nerves nor did it alter eosinophil activation as assessed by major basic protein deposition.

CONCLUSIONS

Antigen sensitization increases vulnerability to parathion-induced airway hyperreactivity and changes the mechanism to one that is dependent on IL-5. Because sensitization to allergens is characteristic of 50% of the general population and 80% of asthmatics (including children), these findings have significant implications for OP risk assessment, intervention, and treatment strategies.

Impact of traffic flow on the asthma prevalence among school children in Lima, Peru

OBJECTIVE

To estimate the impact of traffic flow on the prevalence of asthma among school children of 6 to 7 and 13 to 14-years of age.

METHODS

A cross-sectional study consisting of 5,917 children selected in schools of the Cone Norte of Lima, Peru.

RESULTS

For the 6- to 7-year age group the prevalence of medical diagnosis of asthma according to the traffic flow index was 8.6% (CI: 6.8-10.8), 10.3% (CI: 8.4-12.4), and 15.3% (CI:13.3-17.5) at low, medium and high, respectively, and for the 13- to 14-year age group, 11.9% (CI: 9.4-14.6), 13.3% (CI: 11.6-15.2), and 17.1% (CI: 14.7-19.6).

CONCLUSIONS

For both groups, the prevalence of asthma was significantly related to traffic flow density.

The impact of spirometry on pediatric asthma diagnosis and treatment

Research has shown that spirometry is underutilized in the clinical setting. This study profiles the use of spirometry in an asthma management program at an inner-city community health clinic. Eligible subjects included 56 children who presented with an acute asthma exacerbation. Physicians recorded patient diagnosis before and after viewing spirometry. Bivariate and multivariate analysis was used to determine associations between symptoms and forced expiratory volume in 1 second (FEV1). Physicians changed 30.4% of patients' treatment plans after viewing spirometry results. Wheezing was significantly associated with FEV1 in bivariate analysis; however, multivariate modeling failed to identify significant relationships. The use of spirometry influenced patient diagnosis and treatment.

Asthma care and management before an emergency department visit in children in western Michigan: how well does care adhere to guidelines?

OBJECTIVES

Asthma is one of the more common reasons for children's visits to the emergency departments (EDs). Many studies show that the level of asthma care and self-management in children before an ED visit for asthma is often inadequate; however, most of these studies have been conducted in the inner cities of large urban areas. Our objectives were to describe asthma care and management in children treated for asthma in 3 EDs located in an urban, suburban, or rural setting.

METHODS

We studied a prospective patient cohort consisting of children aged 2 to 17 years who presented with an acute asthma exacerbation at 3 EDs in western Michigan. An in-person questionnaire was administered to the parent or guardian during the ED visit. Information was collected on demographics; asthma history; usual asthma care; frequency of symptoms during the last 4 weeks; current asthma treatment, management, and control; and past emergency asthma care. A telephone interview conducted 2 weeks after the ED visit obtained follow-up information. The 8 quality indicators of asthma care and management were defined based on recommendations from national guidelines.

RESULTS

Of 197 children, 70% were enrolled at the urban site, 18% at the suburban site, and 12% at the rural site. The average age was 7.9 years; 60% were male, and 33% were black. At presentation, nearly half (46%) of the children had mild intermittent asthma, 20% had mild persistent asthma, 15% had moderate persistent asthma, and 19% had severe persistent asthma. One quarter of the children had been hospitalized for asthma, and two thirds had at least 1 previous ED visit in the past year. At least 94% had health insurance coverage and 95% reported having a primary care provider. Less than half of the children had attended at least 2 scheduled asthma appointments with their regular asthma care provider in the past year. Although only 5% of the subjects reported that the ED was their only source of asthma care, at least 30% reported that they always went directly to the ED when they needed urgent asthma care. Only 3 in 5 children possessed either a spacer or a peak-flow meter, whereas approximately 2 in 5 reported having a written asthma action plan. Among those with persistent asthma, there was considerable evidence of undertreatment, with 36% not on either an inhaled corticosteroid or a suitable long-term control medication. Only 20% completed a visit with their regular asthma care provider within 1 week of their ED visit.

CONCLUSIONS

Despite very high levels of health care coverage and access to primary care, the overall quality of asthma care and management fell well short of that recommended by national guidelines.

Asthma among rural Minnesota adolescents

This study examined the prevalence of and risk factors for wheezing and asthma in rural Minnesota adolescents. A survey querying about wheezing, asthma, farm residence, and other respiratory-related factors was administered to all 9th to 11th grade students (N = 13,490) in a stratified, random sample of high schools in rural Minnesota. Nearly one in 8 (12.6%) students reported ever-diagnosed asthma, and 9.2% reported current asthma. Students living on farms reported less wheezing and asthma than rural non-farm students. Obesity and smoking were associated with wheezing and asthma in all rural adolescents. Asthma rates increased with age among girls and may be largely accounted for by simultaneous increases in smoking rates. Despite the apparent protective effect of farm residence, asthma remains a significant public health issue among rural Minnesota adolescents.

Asthma in rural America

OBJECTIVES

To examine current trends of asthma prevalence, diagnosis, and utilization of care in rural areas, increase awareness about asthma disease burden, and provide general recommendations for improving care in this setting.

DATA SOURCES

MEDLINE searches were conducted for articles published from 1966 onward, with human subjects and the English language as descriptors. Other terms used included undiagnosed frequent wheezing, hygiene hypothesis, atopic sensitization, endotoxin, telemedicine, and asthma prevalence and care in rural or urban areas.

STUDY SELECTION

Review and original research studies that reported on asthma care in rural areas were selected for evaluation.

RESULTS

Contrary to common belief, evidence suggests that asthma prevalence of rural and urban youth is comparable in the United States and may indeed be higher in rural areas. Data are not available to determine prevalence rates for rural adults in the United States. This review presents data suggesting that the utilization of asthma care among rural and urban residents may not be comparable. Rural residents are confronted with certain barriers to care that are not as common in the urban setting. These include lack of health care insurance, geographic obstacles to obtaining care, inability of getting suitable appointments, scarcity of health care professionals, and poor access to information about asthma.

CONCLUSIONS

Current literature suggests that asthma in rural areas may be underdiagnosed and deserves additional study. Improving formal and continuing education of health care professionals, compensating for health care shortages by using existing resources, and facilitating patient support and education are some of the ways to address the special needs faced by rural residents.

Mechanisms of organophosphate insecticide-induced airway hyperreactivity

It has been suggested that pesticide exposure may be a contributing factor underlying the increased incidence of asthma in the United States and other industrialized nations. To test this hypothesis, airway hyperreactivity was measured in guinea pigs exposed to chlorpyrifos, a widely used organophosphate pesticide. Electrical stimulation of the vagus nerves caused frequency-dependent bronchoconstriction that was significantly potentiated in animals 24 h or 7 days after a single subcutaneous injection of either 390 mg/kg or 70 mg/kg of chlorpyrifos, respectively. Mechanisms by which chlorpyrifos may cause airway hyperreactivity include inhibition of acetylcholinesterase (AChE) or dysfunction of M3 muscarinic receptors on airway smooth muscle or of autoinhibitory M2 muscarinic receptors on parasympathetic nerves in the lung. AChE activity in the lung was significantly inhibited 24 h after treatment with 390 mg/kg of chlorpyrifos, but not 7 days after injection of 70 mg/kg of chlorpyrifos. Acute exposure to eserine (250 microg/ml) also significantly inhibited lung AChE but did not potentiate vagally induced bronchoconstriction. Neuronal M2 receptor function was tested using the M2 agonist pilocarpine, which inhibits vagally induced bronchoconstriction in control animals. In chlorpyrifos-treated animals, pilocarpine dose-response curves were shifted significantly to the right, demonstrating decreased responsiveness of neuronal M2 receptors. In contrast, chlorpyrifos treatment did not alter methacholine-induced bronchoconstriction, suggesting that chlorpyrifos does not alter M3 muscarinic receptor function on airway smooth muscle. These data demonstrate that organophosphate insecticides can cause airway hyperreactivity in the absence of AChE inhibition by decreasing neuronal M2 receptor function.

Organic dust toxic syndrome: a review

Because of differences in presentation, clinical course, diagnostic testing, treatments, prognosis, followup requirements and prevention strategies between ODTS, hypersensitivity pneumonitis, oxides of nitrogen and other pulmonary exposure-related illnesses, it is important for poison centers and clinicians to obtain appropriate elements of history, physical examination, and laboratory data that will allow an accurate diagnosis.

Chemical predictors of wheeze among farmer pesticide applicators in the Agricultural Health Study

Pesticides may contribute to respiratory symptoms among farmers. Using the Agricultural Health Study, a large cohort of certified pesticide applicators in Iowa and North Carolina, we explored the association between wheeze and pesticide use in the past year. Self-administered questionnaires contained items on 40 currently used pesticides and pesticide application practices. A total of 20,468 applicators, ranging in age from 16 to 88 years, provided complete information; 19% reported wheezing in the past year. Logistic regression models controlling for age, state, smoking, and history of asthma or atopy were used to evaluate associations between individual pesticides and wheeze. Among pesticides suspected to contribute to wheeze, paraquat, three organophosphates (parathion, malathion, and chlorpyrifos), and one thiocarbamate (S-ethyl-dipropylthiocarbamate [EPTC] ) had elevated odds ratios (OR). Parathion had the highest OR (1.5, 95% confidence interval [CI] 1.0, 2.2). Chlorpyrifos, EPTC, paraquat, and parathion demonstrated significant dose-response trends. The herbicides, atrazine and alachlor, but not 2,4-D, were associated with wheeze. Atrazine had a significant dose-response trend with participants applying atrazine more than 20 days/year having an OR of 1.5 (95% CI 1.2,1.9). Inclusion of crops and animals into these models did not significantly alter the observed OR. These associations, though small, suggest an independent role for specific pesticides in respiratory symptoms of farmers.

Managing asthma within the context of the rural family

The purpose of this qualitative study was to describe the experiences of rural families caring for children with asthma. The chief caregivers from six rural families were interviewed about the family's daily experiences in living with asthma, their knowledge of asthma triggers, and strategies for managing asthma. Parental knowledge about asthma and asthma management strategies was quite good. The cost of asthma regimens and school policies about medications were major barriers to better control. Other management strategies were directed at maintaining normality of family life.

Role of rural school nurses in asthma management

Environmental, socioeconomic, psychological and familial factors in rural communities predispose children to asthma. This is not only the case in the US but also in the UK, New Zealand and other Western countries. Asthma prevalence ranges from 2.2 to 15%. Because children spend at least 6 hours of their day in school, school health personnel must be attentive to, and skilled in managing the needs and issues faced by children with asthma while at school. Rural school nurses or their deputies need to advise children with asthma about avoiding aeroallergens from hay, smoke, dust, grain in silos and animal dander from cattle and sheep. In the case of children with asthma in rural areas, symptoms may be accepted as long as the child can go to school and play. Parents in rural areas may not believe in routine preventive care for asthma as part of public health practice. Rural nurses need to be aware of current asthma guidelines and apply the concepts to prevention. They need to be proactive and engage in primary, secondary and tertiary prevention. Rural school nurses can begin by using existing resources and adapting these resources for use in rural school environments. Worldwide asthma education is fundamental to asthma patient management.