Is asthma a vanishing disease? A study to forecast the burden of asthma in 2022

Association of blood lipid profiles and asthma: A bidirectional two-sample Mendelian randomization study

BACKGROUND

Observational studies and meta-analyses have indicated associations between blood lipid profiles and asthma. However, the causal association is unknown. Therefore, this study investigated the causal relationship between blood lipid profiles and asthma using bidirectional Mendelian randomization analysis.

METHODS AND MATERIALS

Our analyses were performed using individual data from the Taiwan Biobank and summary statistics from the Asian Genetic Epidemiology Network (AGEN). The causal estimates between all genetic variants, exposures of interest and asthma were calculated using an inverse-variance weighted method based on Taiwan Biobank data from 24,853 participants (mean age, 48.8 years; 49.8% women). Sensitivity analyses, including the weighted median, MR Egger regression, MR-PRESSO, mode-based estimate, contamination mixture methods, and leave-one-out analysis, were applied to validate the results and detect pleiotropy.

RESULTS

In the inverse-variance weighted (IVW) analyses, we found evidence of a significant causal effect of an increased level of low-density lipoprotein cholesterol on asthma risk (βIVW = 1.338, p = 0.001). A genetically decreased level of high-density lipoprotein cholesterol was also associated with asthma risk (βIVW = -0.338, p = 0.01). We also found that an increased level of total cholesterol was associated with an increased risk of asthma (βIVW = 1.343, p = 0.001). Several sensitivity analyses generated consistent findings. We did not find evidence to support the causality between asthma and blood lipid profiles in either direction.

CONCLUSION

Our results supported the causal relationship between higher levels of LDL cholesterol and total cholesterol and lower levels of HDL cholesterol with an increased risk of asthma.

Pediatric asthma incidence rates in the United States from 1980 to 2017

BACKGROUND

Few studies have examined longitudinal asthma incidence rates (IRs) from a public health surveillance perspective.

OBJECTIVE

Our aim was to calculate descriptive asthma IRs in children over time with consideration for demographics and parental asthma history.

METHODS

Data from 9 US birth cohorts were pooled into 1 population covering the period from 1980 to 2017. The outcome was earliest parental report of a doctor diagnosis of asthma. IRs per 1,000 person-years were calculated.

RESULTS

The racial/ethnic backgrounds of the 6,283 children studied were as follows: 55% European American (EA), 25.5% African American (AA), 9.5% Mexican-Hispanic American (MA) and 8.5% Caribbean-Hispanic American (CA). The average follow-up was 10.4 years (SD = 8.5 years; median = 8.4 years), totaling 65,291 person-years, with 1789 asthma diagnoses yielding a crude IR of 27.5 per 1,000 person-years (95% CI = 26.3-28.8). Age-specific rates were highest among children aged 0 to 4 years, notably from 1995 to 1999, with a decline in EA and MA children in 2000 to 2004 followed by a decline in AA and CA children in 2010 to 2014. Parental asthma history was associated with statistically significantly increased rates. IRs were similar and higher in AA and CA children versus lower but similar in EA and MA children. The differential rates by sex from birth through adolescence principally resulted from a decline in rates among males but relatively stable rates among females.

CONCLUSIONS

US childhood asthma IRs varied dramatically by age, sex, parental asthma history, race/ethnicity, and calendar year. Higher rates in the 0- to 4-year-olds group, particularly among AA/CA males with a parental history of asthma, as well as changes in rates over time and by demographic factors, suggest that asthma is driven by complex interactions between genetic susceptibility and variation in time-dependent environmental and social factors.

Re-Accessing Mental Health Care After Age 18: A Longitudinal Cohort Study of Youth Involved with Community-based Child and Youth Mental Health Agencies in Ontario

OBJECTIVE

About 20-26% of children and youth with a mental health disorder (depending on age and respondent) report receiving services from a community-based Child and Youth Mental Health (CYMH) agency. However, because agencies have an upper age limit of 18-years old, youth requiring ongoing mental health services must "transition" to adult-oriented care. General healthcare providers (e.g., family physicians) likely provide this care. The objective of this study was to compare the likelihood of receiving physician-based mental health services after age 18 between youth who had received community-based mental health services and a matched population sample.

METHOD

A longitudinal matched cohort study was conducted in Ontario, Canada. A CYMH cohort that received mental health care at one of five CYMH agencies, aged 7-14 years at their first visit (N=2,822), was compared to age, sex, region-matched controls (N=8,466).

RESULTS

CYMH youth were twice as likely as the comparison sample to have a physician-based mental health visit (i.e., by a family physician, pediatrician, psychiatrists) after age 18; median time to first visit was 3.3 years. Having a physician mental health visit before age 18 was associated with a greater likelihood of experiencing the outcome than community-based CYMH services alone.

CONCLUSION

Most youth involved in community-based CYMH agencies will re-access services from physicians as adults. Youth receiving mental health services only within community agencies, and not from physicians, may be less likely to receive physician-based mental health services as adults. Collaboration between CYMH agencies and family physicians may be important for youth who require ongoing care into adulthood.

Models for estimating and projecting global, regional and national prevalence and disease burden of asthma: a systematic review

Background

Statistical models are increasingly being used to estimate and project the prevalence and burden of asthma. Given substantial variations in these estimates, there is a need to critically assess the properties of these models and assess their transparency and reproducibility. We aimed to critically appraise the strengths, limitations and reproducibility of existing models for estimating and projecting the global, regional and national prevalence and burden of asthma.

Methods

We undertook a systematic review, which involved searching Medline, Embase, World Health Organization Library and Information Services (WHOLIS) and Web of Science from 1980 to 2017 for modelling studies. Two reviewers independently assessed the eligibility of studies for inclusion and then assessed their strengths, limitations and reproducibility using pre-defined quality criteria. Data were descriptively and narratively synthesised.

Results

We identified 108 eligible studies, which employed a total of 51 models: 42 models were used to derive national level estimates, two models for regional estimates, four models for global and regional estimates and three models for global, regional and national estimates. Ten models were used to estimate the prevalence of asthma, 27 models estimated the burden of asthma – including, health care service utilisation, disability-adjusted life years, mortality and direct and indirect costs of asthma – and 14 models estimated both the prevalence and burden of asthma. Logistic and linear regression models were most widely used for national estimates. Different versions of the DisMod-MR- Bayesian meta-regression models and Cause Of Death Ensemble model (CODEm) were predominantly used for global, regional and national estimates. Most models suffered from a number of methodological limitations – in particular, poor reporting, insufficient quality and lack of reproducibility.

Conclusions

Whilst global, regional and national estimates of asthma prevalence and burden continue to inform health policy and investment decisions on asthma, most models used to derive these estimates lack the required reproducibility. There is a need for better-constructed models for estimating and projecting the prevalence and disease burden of asthma and a related need for better reporting of models, and making data and code available to facilitate replication.

Effects of Rurality and Geographical Distance on Unplanned Emergency Department Utilization for Children With Asthma: A Population Level Retrospective Cohort Study

BACKGROUND

Asthma is a highly prevalent chronic disease among Ontario children; however, the extent to which rural status and distance are associated with unplanned emergency department (ED) use by this population is largely unknown.

OBJECTIVE

To explore the impact of rurality and geographical distance to primary and specialist care services on healthcare utilization by analyzing the use of unplanned ED services.

METHODS

A population level retrospective cohort study of Ontario children ages 5-14 with newly diagnosed asthma was conducted using health administrative data from Institute for Clinical Evaluative Sciences (ICES). Adjusted logistic regression models were used to analyze the association between unplanned ED use with rural status and distance to general practitioner/family physician (GP/FP) and specialist healthcare services, while controlling for confounders.

RESULTS

In total, 19,732 individuals met the inclusion criteria. Individuals who lived in rural locations (OR 2.00, 95% CI 1.64-2.44) and travelled >50 km to a GP/FP (OR 1.25, 95% CI 1.06-1.48) or specialist (OR 1.20, 95% CI 1.05-1.38) were more likely to utilize an ED.

CONCLUSION

Children with asthma utilize healthcare services differently based on rural status and distance to services. To ensure equitable access to care, there is a need to accommodate for these factors in the planning and provision of asthma healthcare services.

Developments in asthma incidence and prevalence in Alberta between 1995 and 2015

BACKGROUND

Asthma is a chronic respiratory disease characterized by reversible bronchoconstriction and airway inflammation. According to Statistics Canada in 2014, 8.1% of Canadians aged 12 and older reported having asthma diagnosed by a health care professional. Therefore, in 2014 there were an estimated 274,661 persons with asthma in Alberta. Most epidemiological studies estimate prevalence and incidence using survey-based data, which has limitations. The Ontario Asthma Surveillance Information System (OASIS) group has developed and validated an algorithm for epidemiologic asthma studies using provincial health databases. In Alberta, there are some studies using provincial databases, but most are restricted to emergency department visits and do not represent the entire asthma population. Using the validated asthma definition for epidemiologic studies, we performed an analysis of the Alberta Health administrative databases to investigate and report province-wide asthma prevalence, incidence and mortality in Alberta from 1995 to 2015.

METHODS

Data from administrative databases, provided by Alberta Health, was analyzed to determine age and sex specific prevalence, incidence and mortality of the asthma population. The population cohort was all individuals residing in the province of Alberta, ages 0 to 99 from 1995-2015. Kendall's Tau coefficient test was used to ascertain whether the observed trends were statistically significant.

RESULTS

Between 1995 and 2015, the age-standardized incidence of asthma decreased by more than 50% in both males and females. Prevalence, however, increased threefold over the 20 years (for both genders) from 3.9 to 12.3% (Tau = 1.00, p < 0.0001) in females and from 3.5 to 11.6% (Tau = 1.00, p < 0.0001) in males. Thus, in 2015 there were 496,927 people with asthma in Alberta. All-cause mortality in the asthma population decreased over time, in both females (Tau = - 0.71, p < 0.0001) and males (Tau = - 0.69, p = 0.0001). For the last several years, all-cause mortality was higher in those with asthma. There were ~ 7 deaths/1000 in the population with asthma versus ~ 5 deaths/1000 in those without asthma.

CONCLUSIONS

The incidence of asthma decreased in both females and males while prevalence continued to increase, although at a slower rate than previously. All-cause mortality in asthma patients was higher than in those without asthma, but both decreased over time.

Evaluating the Clinical Effect of Female Blood Donors of Child-Bearing Age on Maternal and Neonatal Outcomes: A Cohort Study

Iron deficiency is a global problem in women of child-bearing age and is associated with adverse maternal and newborn outcomes. Repeated blood donations deplete iron stores and decrease hemoglobin levels. However, the clinical impact of iatrogenic iron deficiency on mothers and neonates due to blood donation is uncertain. The objective of this study was to assess the association between repeated blood donations in female donors of child-bearing age and the associated risk of adverse maternal and neonatal outcomes. We undertook an observational cohort study of all women who delivered a live or stillborn infant in Ontario, Canada, between 1 January 2010 and 31 March 2012 using birth record data from the Better Outcomes Registry & Network, Canadian Blood Services, and the Institute of Clinical Evaluative Sciences. Only a woman's first pregnancy within the study time frame was included for analysis. We excluded women <18 years or >50 years of age at the time of delivery and multiple birth pregnancies. Data on all female donors who made whole blood donations between 1 January 2007 and 31 March 2012 were obtained from Canadian Blood Services. The primary newborn outcome was diagnosis of a small-for-gestational-age neonate (less than 10th centile). Secondary outcomes were preterm birth, stillbirth, APGAR <4 at 5 minutes, cord pH <7, neonatal death, maternal transfusion, infection, preeclampsia, gestational hypertension, gestational diabetes, placental abruption, and maternal death. Regression models evaluated the effect of repeated donation and the time interval between donations and conception on neonatal and maternal outcomes while adjusting for important clinical and demographic risk factors. A total of 260 037 women delivered live or stillborn singleton infants between 1 January 2010 and 31 March 2012. A total of 7919 (3.0%) women were blood donors, with a mean of 2.43 ± 2.10 lifetime donations. Mean maternal age at the time of delivery for nondonors and donors was 30.30 ± 5.38 and 29.74 ± 4.94 years, respectively. Small for gestational age occurred in 23 706 (9.4%) of neonates born to nondonors and 526 (6.6%) of neonates born to donors. There was a reduction in the risk of small for gestational age with increasing number of lifetime donations (adjusted odds ratio 0.89 [0.86-0.92] per additional donation). For the prespecified secondary outcomes, we observed a reduction in the risk of low birth weight (adjusted odds ratio 0.95 [0.91-0.98] per additional donation). There was no association with other secondary neonatal or maternal outcomes except for maternal hypertension. Proximity of donation to conception had no effect on risk of a small-for-gestational age neonate. Our data suggest that there is no increased risk of deleterious neonatal and maternal outcomes associated with repeated blood donations prior to pregnancy. Although possibly a result of a healthy donor effect, our findings are reassuring to female donors and their children as well as to clinicians and blood system stakeholders seeking to inform policy decisions.

Age, period, and cohort effects on asthma prevalence in Canadian adults, 1994-2011

PURPOSE

To examine the age, period, and cohort effects on asthma prevalence among Canadian adults from 1994/1995 to 2010/2011.

METHODS

Using data from the National Population Health Survey, 13,616 Canadian adults were followed for 16 years. Age was limited to 18-80 years during follow-up. Modified Poisson regression models with generalized estimating equations were used to estimate age, period, and cohort effects on asthma and active asthma prevalence after accounting for sociodemographic factors. Model-based standardization was performed to estimate standardized rates.

RESULTS

Overall asthma prevalence increased from 5% in 1994/1995 to 11% in 2010/2011; decreasing from 12% for 20-year-olds to 6% for 50-60-year-olds and then increased to 8% for 80-year-olds. Individuals aged 20 years had the steepest increase in prevalence between 1994/1995 and 2010/2011. Active asthma prevalence increased from 5% in 1994/1995 to 8% in 2010/2011; decreasing from 8% for 20-year-olds to 5% for 50-60-year-olds and then increased to 6% for 80-year-olds.

CONCLUSIONS

Our findings suggest the presence of age, period, and cohort effects on prevalence of asthma overall and presence of age and period effects on active asthma prevalence in Canadian adults.

Associations between Neighborhood Walkability and Incident and Ongoing Asthma in Children

RATIONALE

Childhood asthma has shown variable associations with children's physical activity. Neighborhood walkability captures community features that promote walking and is protective against some chronic conditions, such as obesity and diabetes.

OBJECTIVES

We evaluated associations between home neighborhood walkability and incident and ongoing childhood asthma.

METHODS

In this population-based cohort study, we used prospectively collected administrative healthcare data for the Province of Ontario housed at the Institute for Clinical Evaluative Sciences. We followed an administrative data cohort of 326,383 Toronto children born between 1997 and 2003, inclusive, until ages 8-15 years. Home neighborhood walkability quintile was measured using a validated walkability index with four dimensions: population density, dwelling density, access to retail and services, and street connectivity. Incident asthma was defined by time of entry into the validated Ontario Asthma Surveillance Information System database, which requires two outpatient visits for asthma within two consecutive years or any hospitalization for asthma and follows children with asthma longitudinally starting at any age. Associations between walkability and incident asthma were examined using Cox proportional hazards models. Associations between ongoing asthma and walkability in each year of life were examined using generalized linear mixed models.

RESULTS

Twenty-one percent of children (n = 69,628) developed incident asthma and were followed longitudinally in the Ontario Asthma Surveillance Information System database. Low birth home neighborhood walkability was associated with an increased incidence of asthma (hazard ratio, 1.11; 95% confidence interval, 1.08-1.14). Among children with asthma, low walkability in a given year of a child`s life was associated with greater odds of ongoing asthma in the same year (odds ratio, 1.12; 95% confidence interval, 1.09-1.14).

CONCLUSIONS

Children living in neighborhoods with low walkability were at increased risk of incident and ongoing asthma. Neighborhood walkability improvement, such as by adding pedestrian paths to improve street connectivity, offers potential strategies to contribute to primary asthma prevention.

Investigating Youth Sport Coach Perspectives of an Asthma Education Module

Physical activity can reduce symptoms and improve wellbeing in people who have asthma, and organized sport is one way for children and youth with asthma to engage in exercise. While asthmatic youth may experience a number of barriers to sport participation, healthy physical and social sport environments supported by coaches can help asthmatic youth athletes maintain long-term engagement in activity. This paper reports results of an assessment of an online coach education tool related to air quality, physical activity, and allergic disease (e.g., asthma). Focus groups with youth team sport coaches in southern Ontario (n = 12 participants) were conducted to explore how users experience the module and short- and medium-term outcomes of implementation. Although coaches perceive the module as relevant, it is considered less valuable in certain contexts (e.g., indoor environments) or when compared with other coach education (e.g., tactical). Although broad asthma management behaviours (e.g., athlete medical forms) were recognized, specific module-identified prevention and management techniques (e.g., the Air Quality Health Index) were less frequently described. Ensuring environment and health coach education emphasizes athlete performance while reducing risk is critical to promoting module application and providing safe and enjoyable youth team sport spaces.

The projected economic and health burden of sub-optimal asthma control in Canada

BACKGROUND

Achieving optimal control is the primary objective of asthma management. However, despite the existence of effective treatments, many patients experience periods of sub-optimal asthma control. The objective of this study was to quantify and project the future economic and health burden of sub-optimal asthma control in Canada.

METHODS

A probabilistic time-in-state model of asthma was created with inputs from published studies on the prevalence of asthma, levels of asthma control, and the impact of asthma control on costs and quality of life. In the primary analysis, we modeled the 20-year total direct costs (in 2014 Canadian dollars) and quality-adjusted life years (QALYs) from 2014 to 2033 in Canada. In the secondary analysis, we also incorporated indirect costs.

RESULTS

The undiscounted projected 20-year direct costs and QALYs lost attributable to sub-optimal asthma control were $24.40 billion and 1.82 million, respectively, from 2014 to 2033. The corresponding discounted values (at 3%) were $18.54 billion and 1.38 million. When indirect costs were considered, the total undiscounted and discounted costs of sub-optimal control were projected to be $280.49 billion, and $213.10 billion, respectively. A 10% reduction in prevalence of sub-optimal control in asthma was associated with 18% reduction in the economic and health burden of asthma over this time period.

DISCUSSION

Sub-optimal asthma control is associated with a substantial economic and health burden. Given that with evidence-based disease management asthma can be controlled in the majority of patients, strategies towards improving asthma management can be associated with a significant return on investment.

TRIAL REGISTRATION

not applicable.

Influences of environmental bacteria and their metabolites on allergies, asthma, and host microbiota

The prevalence of allergic diseases and asthma has dramatically increased over the last decades, resulting in a high burden for patients and healthcare systems. Thus, there is an unmet need to develop preventative strategies for these diseases. Epidemiological studies show that reduced exposure to environmental bacteria in early life (eg, birth by cesarean section, being formula-fed, growing up in an urban environment or with less contact to various persons) is associated with an increased risk to develop allergies and asthma later in life. Conversely, a reduced risk for asthma is consistently found in children growing up on traditional farms, thereby being exposed to a wide spectrum of microbes. However, clinical studies with bacteria to prevent allergic diseases are still rare and to some extent contradicting. A detailed mechanistic understanding of how environmental microbes influence the development of the human microbiome and the immune system is important to enable the development of novel preventative approaches that are based on the early modulation of the host microbiota and immunity. In this mini-review, we summarize current knowledge and experimental evidence for the potential of bacteria and their metabolites to be used for the prevention of asthma and allergic diseases.

Models for estimating and projecting global, regional and national prevalence and disease burden of asthma: protocol for a systematic review

INTRODUCTION

Models that have so far been used to estimate and project the prevalence and disease burden of asthma are in most cases inadequately described and irreproducible. We aim systematically to describe and critique the existing models in relation to their strengths, limitations and reproducibility, and to determine the appropriate models for estimating and projecting the prevalence and disease burden of asthma.

METHODS

We will search the following electronic databases to identify relevant literature published from 1980 to 2017: Medline, Embase, WHO Library and Information Services and Web of Science Core Collection. We will identify additional studies by searching the reference list of all the retrieved papers and contacting experts. We will include observational studies that used models for estimating and/or projecting prevalence and disease burden of asthma regarding human population of any age and sex. Two independent reviewers will assess the studies for inclusion and extract data from included papers. Data items will include authors' names, publication year, study aims, data source and time period, study population, asthma outcomes, study methodology, model type, model settings, study variables, methods of model derivation, methods of parameter estimation and/or projection, model fit information, key findings and identified research gaps. A detailed critical narrative synthesis of the models will be undertaken in relation to their strengths, limitations and reproducibility. A quality assessment checklist and scoring framework will be used to determine the appropriate models for estimating and projecting the prevalence anddiseaseburden of asthma.

ETHICS AND DISSEMINATION

We will not collect any primary data for this review, and hence there is no need for formal National Health Services Research Ethics Committee approval. We will present our findings at scientific conferences and publish the findings in the peer-reviewed scientific journal.

Neurofibromatosis Clinic: A Report on Patient Demographics and Evaluation of the Clinic

BACKGROUND

Neurofibromatosis type 1 (NF1) is a common single-gene disorder. A multidisciplinary approach to the management of NF1 patients is necessitated by the heterogeneity of clinical manifestations. Although multidisciplinary paediatric clinics have been well established, there is a dearth of such resources for adults with NF1. Herein we report our one-year institutional experience with a multidisciplinary adult NF1 clinic.

METHODS

A multidisciplinary team was assembled, and an NF Patient Registry Initiative questionnaire was adapted to collect patient-reported data during clinics. Multiple databases were searched to identify publications pertaining to the experience of other multidisciplinary NF1 clinics focusing on adult patients. Data on patient epidemiology and clinical staff were compared to our data.

RESULTS

A total of 77 patients were scheduled, and 68 attended the clinic, of whom 66 completed the intake questionnaire. The demographic and clinical data from this Canadian population are mostly consistent with previous reports, with some exceptions. Clinical data related to immune system involvement such as asthma, airway/breathing-related difficulties or allergies were striking in our NF1 population. Six relevant published reports of other NF1 clinics were identified. Reports from these studies pertained to periods ranging from 10 to 38 months, and the number of adults assessed ranged from 19 to 177 patients.

CONCLUSIONS

The structure of our clinic and the patient volume are comparable to those of other established centres found in the literature. Our data offer valuable cross-sectional prevalence statistics in the Canadian population. The patient-reported data concerning involvement of the immune system contribute to an emerging recognized medical concern within the NF1 population and warrant further clinical and basic investigation.

Seventy Years of Asthma in Italy: Age, Period and Cohort Effects on Incidence and Remission of Self-Reported Asthma from 1940 to 2010

BACKGROUND

It is well known that asthma prevalence has been increasing all over the world in the last decades. However, few data are available on temporal trends of incidence and remission of asthma.

OBJECTIVE

To evaluate the rates of asthma incidence and remission in Italy from 1940 to 2010.

METHODS

The subjects were randomly sampled from the general Italian population between 1991 and 2010 in the three population-based multicentre studies: ECRHS, ISAYA, and GEIRD. Individual information on the history of asthma (age at onset, age at the last attack, use of drugs for asthma control, co-presence of hay-fever) was collected on 35,495 subjects aged 20-84 and born between 1925-1989. Temporal changes in rates of asthma incidence and remission in relation to age, birth cohort and calendar period (APC) were modelled using Poisson regression and APC models.

RESULTS

The average yearly rate of asthma incidence was 2.6/1000 (3,297 new cases among 1,263,885 person-years). The incidence rates have been linearly increasing, with a percentage increase of +3.9% (95%CI: 3.1-4.5), from 1940 up to the year 1995, when the rates begun to level off. The stabilization of asthma incidence was mainly due to a decrease in the rates of atopic asthma after 1995, while non-atopic asthma has continued to increase. The overall rate of remission was 43.2/1000person-years, and it did not vary significantly across generations, but was associated with atopy, age at asthma onset and duration of the disease.

CONCLUSIONS

After 50 years of a continuous upward trend, the rates of asthma incidence underwent a substantial stabilization in the late 90s. Despite remarkable improvements in the treatment of asthma, the rate of remission did not change significantly in the last seventy years. Some caveats are required in interpreting our results, given that our estimates are based on self-reported events that could be affected by the recall bias.

Farm exposures are associated with lower percentage of circulating myeloid dendritic cell subtype 2 at age 6

BACKGROUND

Early life farm exposures have been shown to decrease the risk of allergic diseases. Dendritic cells (DCs) may mediate asthma-protective effect of farm exposures as they play an important role in the development of immunity and tolerance. Our aim was to investigate whether the numbers and phenotypes of circulating DCs at age 6 are associated with farming, asthma, and atopy in a selected sample of French and Finnish children from the PASTURE study.

METHODS

We studied 82 farm and 86 nonfarm children with and without asthma. Using flow cytometry, BDCA1+ CD11c+ myeloid DC1s (mDC1), BDCA3+(high) mDC2s and BDCA2+ plasmacytoid DCs (pDCs) were identified and expressions of CD86, immunoglobulin-like transcript 3 (ILT3) and ILT4 were analyzed. Questionnaires were used to assess prenatal and lifetime patterns of farm exposures and to define asthma. Atopic sensitization was defined by specific IgE measurements.

RESULTS

The percentage of mDC2 cells was lower in farm children (0.033 ± 0.001) than in nonfarm children (0.042 ± 0.001; P = 0.008). Similar associations were found between mDC2 percentage and prenatal (P = 0.02) and lifetime exposure to farm milk (P = 0.03) and stables (P = 0.003), but these associations were not independent from farming. Asthma was positively associated with ILT4 + mDCs (P = 0.04) and negatively with CD86 + pDCs (P = 0.048) but only in nonfarm children.

CONCLUSIONS

Inverse association between farm exposure and mDC2 percentage suggest that this DC subset may play a role in farm-related immunoregulation.