A scoping review of asthma and machine learning.

OBJECTIVE: The objective of this study was to determine the extent of machine learning (ML) application in asthma research and to identify research gaps while mapping the existing literature. DATA SOURCES: We conducted a scoping review. PubMed, ProQuest, and Embase Scopus databases were searched with an end date of September 18, 2020. STUDY SELECTION: DistillerSR was used for data management. Inclusion criteria were an asthma focus, human participants, ML techniques, and written in English. Exclusion criteria were abstract only, simulation-based, not human based, or were reviews or commentaries. Descriptive statistics were presented. RESULTS: A total of 6,317 potential articles were found. After removing duplicates, and reviewing the titles and abstracts, 102 articles were included for the full text analysis. Asthma episode prediction (24.5%), asthma phenotype classification (16.7%), and genetic profiling of asthma (12.7%) were the top three study topics. Cohort (52.9%), cross-sectional (20.6%), and case-control studies (11.8%) were the study designs most frequently used. Regarding the ML techniques, 34.3% of the studies used more than one technique. Neural networks, clustering, and random forests were the most common ML techniques used where they were used in 20.6%, 18.6%, and 17.6% of studies, respectively. Very few studies considered location of residence (i.e. urban or rural status). CONCLUSIONS: The use of ML in asthma studies has been increasing with most of this focused on the three major topics (>50%). Future research using ML could focus on gaps such as a broader range of study topics and focus on its use in additional populations (e.g. location of residence).Supplemental data for this article is available online at http://dx.doi.org/ .

Personal and early life factors associated with new-onset asthma, remission, and persistence of asthma in a 2-year follow-up of schoolchildren.

OBJECTIVE: The natural course of childhood asthma, after its onset, is characterized by periods of persistence, relapse and remission. To investigate personal and early life factors associated with new-onset asthma, persistence and remission among children. METHODS: The study was conducted in the province of Saskatchewan, Canada. Children in grades Kindergarten to Grade 8 (ages 5-14 years) participated in a cross-sectional study in 2013. In 2015, we approached those who gave consent in 2013 to be re-contacted, creating a prospective cohort. Data were collected using questionnaires in both years. Participants in 2013 who also had data in 2015 (25%: n = 324/1,348) had their asthma status reclassified and longitudinal descriptors were applied: "no asthma", "new-onset asthma", "persistent" or "remission". Personal and early life factors associations with asthma outcomes in 2015 were evaluated. RESULTS: Among those without asthma in 2013 (n = 245), the incidence of new-onset asthma in 2015 was 7.2%. Among those with asthma in 2013 (n = 79), 47.1% had remission and 52.9% had persistent asthma in 2015. Parental history of asthma (adjusted odds ratio (aOR): 4.99; 95% confidence interval (CI): 1.88-28.27), early life respiratory infection (aOR: 1.92; 95%CI: 1.47-7.88), early life allergy [aOR: 6.39; 95%CI: 1.34-30.58) and early life infection (aOR: 4.99; 95%CI: 1.19-20.93) were associated with new onset asthma. Similarly, while parental history of asthma (aOR: 1.13; 95%CI: 0.29-4.34), early life respiratory infection (aOR: 2.71; 95%CI: 0.70-10.45), and early life ear infection (aOR: 1.34; 95%CI: 0.36-5.05) were also positively association with persistent asthma, the associations were not statistically significant. CONCLUSION: Parental history of asthma, early life respiratory infection and allergy might not only influence the onset of childhood asthma but also be associated with asthma persistence.

Are Dietary Factors Associated with Lung Function in Canadian Adults?

Purpose: The purpose of this study was to explore the impact of dietary factors and biomarkers on lung function among Canadian adults (18-79 years). Methods: Our data source was the Canadian Health Measures Survey Cycle-3, which included 3397 adults. The household and clinic questionnaires and physical measures were used to assess individual dietary factors, modified Mediterranean Diet Scores, and biomarkers. Results: The overall mean percent predicted values for FVC and FEV1 were 97% and 95%, respectively. While somewhat inconsistent between outcomes, higher lung function was associated with bean, grain, milk, fruit, and vegetable consumption, whereas lower lung function was associated with egg and potato consumption. Among the biomarkers, vitamin D, chloride, total serum protein, and red blood cell folate were associated with higher lung function, whereas C-reactive protein and vitamin B12 was associated with lower lung function. Conclusion: Our study provides support for an association between some dietary factors and lung function, though not entirely consistent between a specific dietary factor and the outcomes studied (FVC, FEV1, FVC/FEV1, and FEF25%-75%). The associations between a specific biomarker and lung function were more consistent (i.e., observed with a larger number of lung function outcomes) than were the dietary factors.

Asthma diagnosis among children along an urban-rural gradient.

OBJECTIVE: Studies have reported lower asthma prevalence in rural compared to urban areas. While environmental factors have mostly been implicated for these differences, the lower asthma prevalence could also be linked to asthma under-diagnosis in rural children. We investigate if rural children experience under-diagnosis of asthma more compared to urban children. METHODS: In 2013, we conducted a cross-sectional survey of schoolchildren across an urban-rural gradient in Saskatchewan, Canada. The participants formed sampling frame for future studies. In 2015, we approached those who gave consent in 2013 for further testing, repeated the survey, and conducted clinical testing. Based on survey responses, children were classified into "no asthma," "at-risk-for-asthma," and "diagnosed asthma." We then classified asthma status as either "no asthma" or "probable asthma" based on a validated asthma algorithm. RESULTS: The study population of 335 schoolchildren (aged 7-17 years) comprised of 73.4% from large urban, 13.7% from small urban, and 12.8% from rural areas. Proportion with report of physician-diagnosed asthma was 28.5% (Large urban), 34.8% (Small urban), and 20.9% (Rural). Mean percent predicted FEV1 and FEF25%-75% were lower in rural compared to small urban and large urban children (p < 0.05). Among those not classified as with "diagnosed asthma" by the survey, the algorithm further identified presence of asthma in 5.5% large urban, 8.1% small urban, and 18.8% rural children (p = 0.03). CONCLUSION: The study revealed evidence of asthma underdiagnosis in rural areas and further supports the use of objective measures in addition to symptoms history when investigating asthma across urban-rural gradients.

The association between endotoxin in house dust with atopy and exercise-induced bronchospasm in children with asthma.

BACKGROUND: Studies have reported protective and adverse associations between microbial exposure and childhood asthma. However, among children with asthma the relationships between endotoxin and exercise-induced bronchospasm (EIB) is less clear. OBJECTIVE: We investigated the association between exposure to endotoxin in house dust with atopy and EIB in children with asthma. METHODS: A cross-sectional survey was conducted among schoolchildren (aged 7-17 years) in the province of Saskatchewan, Canada. A subpopulation with asthma (n = 116) were identified from 335 participants using a validated asthma algorithm. We determined atopy among the asthma subpopulation by skin prick testing (SPT) while EIB was evaluated using exercise challenge testing (ECT). Dust samples were collected from mattress and play area floors, and endotoxin was measured in dust extracts. Logistic regression analyses were used to explore associations between endotoxin with atopy and EIB. RESULTS: Among the 116 children with asthma, 99 completed SPT and all had completed ECT. Of these, 71/99 (71.7%) were atopic and 26/116 (22.4%) had EIB. Exposure to high play area endotoxin concentration [adjusted odds ratio (aOR) = 0.15, 95% CI: 0.03-0.85] and load (aOR = 0.11, 95% CI: 0.02-0.73) were negatively associated with atopy. In contrast, EIB was positively associated with high mattress endotoxin concentration (aOR = 6.01, 95% CI: 1.20-30.13). CONCLUSION: Indoor microbial endotoxin exposure has varied associations with atopy and exercise-induced bronchospasm among children with asthma.

Predictors of Physical Activity Levels in Community-Dwelling Older Adults: A Multivariate Approach Based on a Socio-Ecological Framework.

The purpose of this study was to explore cross-sectional relationships between self-reported physical activity (PA) and personal, social, and environmental factors in community-dwelling adults aged 50 years and older. Accounting for clustering by neighborhood, generalized estimating equations were used to examine associations between selected correlates and the Physical Activity Scale for the Elderly (PASE) score while adjusting for confounders. Data for 601 participants were analyzed: 79% female, 37% married, mean age 76.8 (± 8.7) years, mean PASE score 112.6 (± 64.8). Age, living in seniors' housing, using nursing/home care services, receiving encouragement to be active, and having benches available in the neighborhood were inversely associated with PASE. Self-efficacy, SF-12 score, PA barriers, social support, and the presence of trails showed positive associations. Several personal, social, and environmental factors associated with PA were identified. The inverse association between PA and living in seniors' housing units should be considered when developing PA programs for older adults.

Prevalence, risk factors, and clinical outcomes of atopic and nonatopic asthma among rural children.

BACKGROUND: Because of time and cost constraints, objective classification of atopic and nonatopic asthma has been limited in large epidemiologic studies. However, as we try to better understand exposure-outcome associations and ensure appropriate treatment of asthma, it is important to focus on phenotype-defined asthma classification. OBJECTIVE: To compare atopic and nonatopic asthma in rural children with regard to risk factors and clinical outcomes. METHODS: We conducted a cross-sectional study in rural Saskatchewan, Canada, in 2011. Parents of 6- to 14-year-old children completed a health and exposure survey. Skin prick tests were completed in a subsample of 529 children. Asthma was based physician diagnosis. Asthma status was defined as no asthma, nonatopic asthma, and atopic asthma. RESULTS: Asthma prevalence was 14.7% of which 32.1% of cases were atopic. After adjustment, early respiratory illness and a family history of asthma were predictors of childhood asthma, regardless of atopic status (P < .05). Being overweight and having a dog in the home were associated with an increased risk of nonatopic asthma (P < .05). A mother with a history of smoking increased the risk of atopic asthma (P = .01). Compared with those with nonatopic asthma, in the past 12 months, children with atopic asthma were more likely to report a sneezy, runny, or blocked nose or have shortness of breath (odds ratio >2), whereas those with nonatopic asthma were more likely to have parents who missed work (odd ratio >3). Those with nonatopic asthma had significantly lower forced expiratory volume in 1 second compared w2ith those with atopic asthma. CONCLUSION: Exposures may contribute differentially to atopic and nonatopic asthma and result in differential clinical presentation or burden. The study of these characteristics is important for etiologic understanding and management decisions.

Childhood asthma, asthma severity indicators, and related conditions along an urban-rural gradient: a cross-sectional study.

BACKGROUND: Asthma prevalence is generally lower in rural locations with some indication of an urban-rural gradient. However, among children with asthma, certain rural exposures thought to protect against the development of asthma could aggravate the condition. We examined childhood asthma prevalence and related conditions along an urban-rural gradient and also examined the characteristics of those with asthma along the urban-rural gradient. METHODS: In 2013 we completed a cross-sectional survey of 3509 children aged 5-14 years living in various population densities of Saskatchewan, Canada. Location of dwelling was identified as belonging to one of the following population densities: large urban region (approximately 200,000), small urban (approximately 35,000), or rural (small town of <1,500 or farm dweller). Physician-diagnosed asthma and asthma-related symptoms were ascertained from responses in the parental-completed questionnaires. RESULTS: Of the study population, 69% lived in a large urban region, 11% lived in a small urban centre and 20% were rural dwellers. Overall, asthma prevalence was 19.6% with differences in asthma prevalence with differences between locations (large urban = 20.7%; small urban = 21.5%; rural = 15.1%; p = 0.003). After adjustment for potential confounders, the association between location of dwelling and asthma remained significant. Despite a lower prevalence of asthma in the rural area, the prevalence and risk of ever wheeze and having more than 3 wheezing episodes in the past 12 months among those who reported asthma, was higher in rural locations after adjustment for potential confounders. CONCLUSIONS: The results of this study support the evidence of a difference in childhood asthma prevalence between urban and rural locations and that once a child has asthma, certain rural exposures may aggravate the disease.

Prevalence and associated risk factors of chronic bronchitis in First Nations people.

BACKGROUND: Inadequate housing, low family income, household smoking, personal smoking status, and poor schooling are some of the conditions that have been significantly associated with the prevalence and incidence of chronic bronchitis. The aim of the current study was to determine the prevalence of chronic bronchitis (CB) and associated risk factors among First Nations people. METHODS: An interviewer-administered survey was conducted as part of the First Nations Lung Health Project in 2012 and 2013 with 874 individuals from 406 households in two First Nations communities located in the province of Saskatchewan, Canada. The questionnaire collected information on individual and contextual determinants of health and a history of ever diagnosed with CB (outcome variable) from the two communities participating in the First Nations Lung Health Project. Clustering effect within households was adjusted using Generalized Estimating Equations. RESULTS: The prevalence of CB was 8.9% and 6.8% among residents (18 years and older) of community A and community B respectively and was not significantly different. CB prevalence was positively associated with odour or musty smell of mildew/mould in the house [OR adj (95% CI) = 2.33 (1.21, 4.50)], allergy to house dust [3.49 (1.75, 6.97)], an air conditioner in home [2.33 (1.18, 4.24)], and increasing age [0.99 (0.33, 2.95), 4.26 (1.74, 10.41), 6.08 (2.58, 14.33)]. An interaction exposure to environmental tobacco smoke in the house*body mass index showed that exposure to household smoke increased the risk of CB for overweight and obese participants (borderline). Some of the variables of interest were not significantly associated with the prevalence of CB in multivariable analysis, possibly due to small numbers. CONCLUSIONS: Our results suggest that significant determinants of CB were: increasing age; odour or musty smell of mildew/mould in the house; allergy to house dust; and, body mass index. Modifiable risk factors identified were: (i) community level-housing conditions (such as mould or mildew in home, exposure to environmental tobacco smoke in house); and, (ii) policy level-remediation of mould, and obesity. TRIAL REGISTRATION: Not applicable.

Early farm residency and prevalence of asthma and hay fever in adults.

BACKGROUND: Asthma and hay fever have been found to be both positively and negatively associated with farming lifestyles in adulthood. Lack of congruency may depend upon early life exposure. OBJECTIVE: To assess the importance of different periods of farm residency for asthma and hay fever in an adult Canadian population. METHODS: We conducted a questionnaire survey in rural Saskatchewan, Canada. We assessed a history of asthma and hay fever with five categories of farm residency that were mutually exclusive: first year of life only, currently living on a farm, both first year of life and currently living on a farm, other farm living, and no farm living. Generalized estimating equations were used to adjust for clustering effects of adults within households. RESULTS: Of the 7148 responding, 30.6% had an early farm living experience only, 34.4% had both early and current farm living experiences, while 17.4% had never lived on a farm. The overall prevalence of ever asthma and hay fever was 8.6% and 12.3%, respectively, and was higher in women. Sex modified the associations between ever asthma and hay fever with farm residency variables whereby women had a decreased risk for both asthma [adjusted odds ratio (ORadj): 0.67, 95% confidence interval (CI):0.47-0.96] and hay fever (ORadj: 0.60, 95% CI: 0.44-0.83) with an early farm exposure only. Men currently living on a farm without an early farm exposure had an increased risk for ever asthma (ORadj: 1.82, 95% CI: 1.02-3.24). CONCLUSION: Farm residency in the first year of life shows a protective effect for adult asthma and hay fever that appears to differ by sex.

Prevalence and determinants of atopy and allergic diseases among school-age children in rural Saskatchewan, Canada.

BACKGROUND: There have been few investigations of farming-related activities or specific characteristics resulting in the associations between those exposures and atopic disease. OBJECTIVE: To study the associations between farm-associated exposures and atopic diseases. METHODS: As part of a longitudinal study of lung health in rural residents, a cross-sectional baseline study was conducted in rural Saskatchewan, Canada. This included an initial survey phase followed by a clinical testing phase. A subsample of 584 children (grades 1-8) completed skin prick testing to assess atopic status. Atopy was defined as a positive reaction to any of 6 allergens (local grasses, wheat dust, cat dander, house dust mite, Alternaria species, or Cladosporium species) of at least 3 mm compared with the negative control. RESULTS: Of those who completed clinical testing, the prevalence of atopy was 19.4%, that of hay fever was 8.8%, and that of eczema was 27.4%. Based on skin prick testing, sensitization was highest for cat dander (8.6%) followed by local grasses (8.2%) and house dust mite (5.1%). After adjustment for potential confounders, home location (farm vs non-farm) was not associated with atopic status. However, livestock farming was protective against atopy (adjusted odds ratio 0.38, 95% confidence interval 0.17-0.88). In contrast, current residence on a farm was associated with an increase in the likelihood of hay fever in these children (adjusted odds ratio 3.68, 95% confidence interval 1.29-10.45). Also, regular farming activities in the past year were associated with an increased risk of hay fever. CONCLUSION: In children, livestock exposure has a protective effect on skin prick test positivity, whereas farm living and activities increase the risk of hay fever.

Asthma incidence and risk factors in a national longitudinal sample of adolescent Canadians: a prospective cohort study.

BACKGROUND: Estimates of asthma incidence and its possible determinants in adolescent populations have rarely been obtained using prospective designs. We sought to identify socio-demographic and other patterns in the incidence of asthma among Canadian adolescents and to examine possible behavioural and environmental determinants of asthma incidence using longitudinal analyses. METHODS: We used data from the National Population Health Survey (NPHS), a nationally representative longitudinal survey of Canadians. All persons aged 12-18 years without asthma at baseline were followed up to a maximum of 12 years. The outcome was a reported diagnosis of asthma during the follow-up period. Analyses were weighted to the population and bootstrapping procedures were used to estimate variances. RESULTS: Participants (n = 956) represented 2,038,890 adolescents of whom 293,450 (14.4%) developed asthma over the 21,274,890 person-years of follow-up. Overall, the incidence of asthma was 10.2 per 1000 person-years. In adjusted Cox regression analysis, being female (HR = 2.13, 95% CI = 1.26-3.62, p = 0.005) and being exposed to passive smoking (HR = 2.06, 95% CI = 1.27-3.34, p = 0.003) were associated with the development of asthma while no statistically significant associations were identified for rural residence, being overweight, and other health behaviours. There was also an apparent cohort effect among girls where girls who were older at baseline reported being diagnosed with asthma more over the follow-up than their younger counterparts. This was not observed among males. CONCLUSIONS: Asthma prevention initiatives for adolescents should target girls and focus on smoking exposures. The role that differential diagnostic patterns play in these observations should be investigated to more accurately assess the incidence of asthma.

Factors contributing to risks for pediatric asthma in rural Saskatchewan.

BACKGROUND: Rural children have lower reported rates of asthma compared with urban children. Although reasons for these differences remain unclear, 3 possible explanations exist: (1) environmental differences, (2) variations in health care access, and (3) variations in health risk behaviors. OBJECTIVE: We investigated asthma among children living on farms and in small towns and its potential determinants, including personal, behavioral, and environmental factors. METHODS: School children (n = 842, ages 6-13; participation rate = 72.0%) were involved in a 2003 cross-sectional study. Their parents completed a lung health survey that included questions about asthma, asthma-like symptoms, and potential determinants of asthma (demographic, environmental, health risk behaviors). Participating children were classified into farm dwellers (live on farm or acreage) and small town dwellers. Multiple logistic regression was used to investigate the association between asthma and wheeze with demographic, environmental, and behavioral exposures with simultaneous adjustment for confounders. RESULTS: Asthma and wheeze prevalence was not significantly different between farm and small town areas (current asthma: 16% vs 13%, respectively; current wheeze: 27% vs 21%, respectively) and followed consistent patterns. Factors associated with diagnosed asthma were dampness (odds ratio [OR] = 1.85; 95% confidence interval [CI] = 1.08-3.17), with enrollment in daycare found to be protective (OR = 0.53; 95% CI = 0.33-0.85). Being obese or overweight was associated with wheeze (OR = 1.77; 95% CI = 1.06-2.97). CONCLUSION: Given the differences between areas and the associations between environmental risk factors and obesity with asthma and wheeze, the study findings support environment and health risk behavior explanations for the observed geographic variations.

Endotoxin as a determinant of asthma and wheeze among rural dwelling children and adolescents: a case-control study.

BACKGROUND: The association between endotoxin exposure and asthma is complex and has been associated with rural living. We examined the relationship between domestic endotoxin and asthma or wheeze among rural school-aged children (6-18 years) and assessed the interaction between endotoxin and other characteristics with these outcomes. METHODS: Between 2005 and 2007 we conducted a case-control study of children 6-18 years in the rural region of Humboldt, Canada. Cases (n = 102) reported doctor-diagnosed asthma or wheeze in the past year. Controls (n = 208) were randomly selected from children without asthma or wheeze. Data were collected to ascertain symptoms, asthma history and indoor environmental exposures (questionnaire), endotoxin (dust collection from the play area floor and child's mattress), and tobacco smoke exposure (saliva collection). Statistical testing was completed using multiple logistic regression to account for potential confounders and to assess interaction between risk factors. A stratified analysis was also completed to examine the effect of personal history of allergy. RESULTS: Among children aged 6-12 years, mattress endotoxin concentration (EU/mg) and load (EU/m2) were inversely associated with being a case [odds ratio (OR) = 0.44, 95% confidence interval (CI) = 0.20-0.98; and OR = 0.38, 95% CI = 0.20-0.75, respectively]. These associations were not observed in older children or with play area endotoxin. CONCLUSIONS: Our results suggest that endotoxin exposure might be protective for asthma or wheeze. The protective effect is found in younger school-aged, non-allergic children. These results may help explain the inconsistencies in previous studies and suggest that the protective effects of endotoxin in the prevention of atopy and asthma or wheeze are most effective earlier in life.

Urban-rural differences in asthma prevalence among young people in Canada: the roles of health behaviors and obesity.

BACKGROUND: Asthma prevalence has been reported to be lower in rural regions, but the reasons for this are not known. OBJECTIVE: To confirm the existence of an urban-rural geographic gradient in asthma prevalence among Canadian youths and to evaluate whether this gradient was mediated by health behaviors. METHODS: Cross-sectional data from 4,726 Canadian youth (grades 6-10) were collected during the 2001-02 Health Behaviour in School-Aged Children survey. Geographic region was categorized as metro (urbanized), non-metro but adjacent to metro, and rural. Asthma was defined via self-report of doctors' diagnoses and at least 1 of: (1) asthma symptoms or (2) a health care visit for asthma in the past year. Health behaviors (diet and physical activity) as well as obesity were also assessed. RESULTS: Asthma prevalence was lowest in rural regions (metro = 17.7%, non-metro-adjacent = 15.6%, rural = 14.8%). A lower risk of asthma was associated with rural region (adjusted odds ratio [OR] = 0.76, 95% CI = 0.61-0.95) and living in non-metro-adjacent regions (adjusted OR = 0.81, 95% CI = 0.65-1.01). Health behaviors and obesity status did not mediate the association between geographic region and asthma. Being overweight or obese, having a high physical activity level, and exposure to passive smoking independently elevated the risk of asthma, whereas increased consumption of whole milk or vegetables were each protective. CONCLUSIONS: Although asthma prevalence among youth was lower in rural areas, this association was not mediated by health behaviors or obesity. Other exposures, likely environmental, are the logical mechanisms through which rural geographic status is related to lower asthma prevalence.

Relationship of endotoxin and tobacco smoke exposure to wheeze and diurnal peak expiratory flow variability in children and adolescents.

BACKGROUND AND OBJECTIVE: The relationship between endotoxin exposure and asthma severity (wheeze and airways obstruction) is not well described. The effects of endotoxin and tobacco smoke exposure on self-reported wheeze and diurnal PEF variability (DV-PEF) were examined in children aged 6-18 years with asthma or wheeze. METHODS: A cross-sectional study was performed in a rural area. From this study, children who reported wheeze in the previous 12 months or a physician diagnosis of asthma (n = 98) were selected for a case-control study. These subjects, who were the basis for the present analysis, completed: (i) a home environmental assessment, including dust collection to measure endotoxin levels: (ii) a clinic visit, including saliva collection to measure cotinine levels; and (iii) 2 week monitoring of twice daily symptom records, including wheeze, and PEF to calculate DV-PEF. RESULTS: Among these children, 22.4% reported wheeze during the monitoring period. Greater DV-PEF was associated with higher endotoxin loads in play areas (P < 0.05). The association between salivary cotinine levels and high DV-PEF was modified by gender. In females, higher cotinine levels were associated with an increased risk of high DV-PEF compared with lower cotinine levels (P < 0.05), but this was not observed among males. CONCLUSIONS: Higher endotoxin exposure was associated with greater DV-PEF among children with asthma or wheeze. While previous studies have suggested that endotoxin exposure protects against the development of asthma, individuals with the disease should avoid high exposure levels to limit exacerbations. The effect of tobacco smoke exposure on lung health may differ between male and female children.

Atopy risk among school-aged children in relation to early exposures to a farm environment: A systematic review.

BACKGROUND AND OBJECTIVES: Childhood atopy is a complex condition with both a genetic and an environmental component. This systematic review will explore the current understanding of the importance of early life exposures to a farm in the development of atopy measured by objective markers of skin prick testing, and specific IgE measurements in school age children. METHODS: A systematic review was performed. RESULTS: Among 7285 references identified, 14 studies met the inclusion criteria (13 cross-sectional studies and 1 case-control study). The results were fairly consistent in that early farm-related exposures can protect children from becoming atopic at school age. In general, there was heterogeneity in the assessment of outcomes and exposures. CONCLUSIONS: Early-life farm exposures are associated with a protective effect on childhood atopy as assessed by objective markers. Future work should focus on understanding specific farm exposures that may important in these associations between atopy and farm exposures in children.

The course of asthma: A population-based 10-year study examining asthma remission in children diagnosed with asthma in preschool.

BACKGROUND: The natural course of asthma may differ depending on the age of onset. OBJECTIVE: To investigate predictors of asthma remission with a focus on the age of asthma onset. METHODS: The study was a retrospective birth cohort of children with asthma in Saskatchewan, Canada. Using the Saskatchewan Ministry of Health databases, we identified children with a diagnosis of asthma in the first 6 years of life and who had at least 10 years of follow-up after diagnosis (n = 22 563). Of these, we included 6393 children either with persistent asthma (≥1 physician visit or hospitalization for asthma [PVHA] during each year of follow-up) and those who had remission (had PVHA in the first year after diagnosis but at some point during the follow-up no longer received PVHA until end of the study). We used survival analysis to examine associations between remission and age of asthma onset. RESULTS: Of the study participants, 87.2% had early-onset (≤3 years) and 12.8% had late-onset (4-6 years) asthma. Over the 10-years of follow-up, the rate of asthma remission was 37 per 100 person-years. Early-onset asthma (hazard ratio [HR] = 1.10; 95%confidence interval [CI]: 1.01-1.20), being female (HR = 1.12; 95%CI: 1.07-1.18), living in a rural (HR = 1.20; 95%CI: 1.14-1.27) and medium urban (HR = 1.16; 95%CI: 1.08-1.26) location were positively associated with remission while history of atopy decreased likelihood of remission (HR = 0.73; 95%CI: 0.54-0.97). CONCLUSION: Most children with asthma experienced remission, especially those with the onset of symptoms within the first 3 years of life.