The asthma epidemic and our artificial habitats

Parental occupations and risk for Crohn's disease in children

BACKGROUND AND OBJECTIVES

Lacunae exist on the identity of specific environmental risk factors that associate with Crohn's disease (CD). We hypothesized that indirect exposures acquired via the parents' occupation may confer susceptibility.

METHODS

A case-control study based on children diagnosed with CD (prior to age 20) at a tertiary care gastroenterology clinic in Montreal, Canada was carried out. Population- and hospital-based controls without IBD were selected. Information on occupations held by the parents was acquired from interview. Jobs were coded using the Canadian National Occupational Classification for Statistics. Associations were examined using logistic regression accounting for potential confounders. Odds ratios (OR) and corresponding 95% confidence intervals (CI) were estimated.

RESULTS

A total of 466 cases and 335 controls were studied. The mean (±SD) age of the cases (12.4 ± 3.2) was slightly higher than controls (10.5 ± 4.9). Gender and ethnicity were equally distributed between the groups. Logistic regression analysis suggested that children whose fathers worked as retail salespersons/sales clerks [odds ratio (OR) 3.6, 95% confidence interval (CI) 1.2-11.1], and whose mothers worked as administrative secretaries (OR 3.2, 95% CI 1.6-6.4), were more likely to be at risk for CD. Mothers who worked as either early childhood educators (OR 2.3, 95% CI 0.85-6.2) or as clerks (OR 2.8, 95% CI 0.8-9.9) also appeared to confer risks, but these associations were statistically not significant.

CONCLUSION

Parental occupations related to 'social mixing' that can potentially enhance exposure to infectious agents, appear to confer higher risk for CD in children.

Role of Janus Kinase 3 in Predisposition to Obesity-associated Metabolic Syndrome

Obesity, a worldwide epidemic, is a major risk factor for the development of metabolic syndrome (MetS) including diabetes and associated health complications. Recent studies indicate that chronic low-grade inflammation (CLGI) plays a key role in metabolic deterioration in the obese population. Previously, we reported that Jak3 was essential for mucosal differentiation and enhanced colonic barrier functions and its loss in mice resulted in basal CLGI and predisposition to DSS induced colitis. Since CLGI is associated with diabetes, obesity, and metabolic syndrome, present studies determined the role of Jak3 in development of such conditions. Our data show that loss of Jak3 resulted in increased body weight, basal systemic CLGI, compromised glycemic homeostasis, hyperinsulinemia, and early symptoms of liver steatosis. Lack of Jak3 also resulted in exaggerated symptoms of metabolic syndrome by western high-fat diet. Mechanistically, Jak3 was essential for reduced expression and activation of Toll-like receptors (TLRs) in murine intestinal mucosa and human intestinal epithelial cells where Jak3 interacted with and activated p85, the regulatory subunit of the PI3K, through tyrosine phosphorylation of adapter protein insulin receptor substrate (IRS1). These interactions resulted in activation of PI3K-Akt axis, which was essential for reduced TLR expression and TLR associated NFκB activation. Collectively, these results demonstrate the essential role of Jak3 in promoting mucosal tolerance through suppressed expression and limiting activation of TLRs thereby preventing intestinal and systemic CLGI and associated obesity and MetS.

Lifestyle domains as determinants of wheeze prevalence in urban and rural schoolchildren in Ecuador: cross sectional analysis

BACKGROUND

The acquisition of a modern lifestyle may explain variations in asthma prevalence between urban and rural areas in developing countries. However, the effects of lifestyle on asthma have been investigated as individual factors with little consideration given to the effects of lifestyle as a set of attributes. The aim of the present study was to identify modern lifestyle domains and assess how these domains might explain wheeze prevalence in urban and rural areas.

METHODS

We analysed data from cross-sectional studies of urban and rural schoolchildren in Esmeraldas Province, Ecuador. Variables were grouped as indicators of socioeconomic factors, sedentarism, agricultural activities and household characteristics to represent the main lifestyle features of the study population. We used multiple correspondence analyses to identify common lifestyle domains and cluster analysis to allocate children to each domain. We evaluated associations between domains and recent wheeze by logistic regression.

RESULTS

We identified 2-3 lifestyle domains for each variable group. Although wheeze prevalence was similar in urban (9.4%) and rural (10.3%) schoolchildren, lifestyle domains presented clear associations with wheeze prevalence. Domains relating to home infrastructure (termed transitional, rudimentary, and basic urban) had the strongest overall effect on wheeze prevalence in both urban (rudimentary vs. basic urban, OR = 2.38, 95% CI 1.12-5.05, p = 0.024) and rural areas (transitional vs. basic urban, OR = 2.02, 95% CI 1.1-3.73, p = 0.024; rudimentary vs. basic urban, OR = 1.88, 95% CI 1.02-3.47, p = 0.043). A high level of sedentarism was associated with wheeze in the rural areas only (OR = 1.64, 95% CI 1.23-2.18, p = 0.001).

CONCLUSIONS

We identified lifestyle domains associated with wheeze prevalence, particularly living in substandard housing and a high level of sedentarism. Such factors could be modified through programmes of improved housing and education. The use of lifestyle domains provides an alternative methodology for the evaluation of variations in wheeze prevalence in populations with different levels of development.

Association of vitamin D with respiratory outcomes in Canadian children

BACKGROUND/OBJECTIVES

Vitamin D modifies airway inflammation and appears to be important in building immunity against respiratory infections, and so is potentially beneficial in asthma. However, to date results from studies investigating the relationship of vitamin D with respiratory outcomes are inconsistent. The objective of this study was to determine the association of vitamin D with current wheeze, ever asthma and lung function.

SUBJECTS/METHODS

Data on 1213 children aged 6-12 years, from the Canadian Health Measures Survey, were considered for the study. Serum 25-hydroxy vitamin D (25(OH)D) levels were categorized into three categories: ⩽49 nmol/l (low); 50-74 nmol/l (moderate); and ⩾75 nmol/l (high).

RESULTS

Children in the low and high 25(OH)D categories were more likely to report current wheeze in comparison to those in the moderate category (odds ratio (OR): 3.26, 95% confidence interval (CI): 1.16-9.17 and OR: 2.14, 95% CI: 1.07-4.28, respectively). The results for the association between 25(OH)D levels and ever asthma were similar to those observed for current wheeze, except that a significant association was observed only in the lower category. The rate of increase in forced expiratory volume in one second and forced vital capacity with age was greater in the moderate category.

CONCLUSIONS

Children in both low and high 25(OH)D categories had increased risk of current wheeze and reduced rate of change in lung function with age in comparison to the moderate category, raising the possibility of a U-shaped association between vitamin D levels and respiratory health. Clearer guidelines for optimal vitamin D levels are required to improve respiratory health in children.

A review of epidemiological studies of asthma in Ghana

CONTEXT/BACKGROUND

The last few decades have witnessed a rise in the global prevalence of asthma with a number of risk factors being linked to this increase. Although there is insufficient data on the prevalence of asthma in Ghana, a few studies conducted in this country have shed light on the disease aetiology and associated risk factors.

EVIDENCE ACQUISITION

The purpose of this review is to explore the literature on epidemiological studies on asthma carried out in Ghana and how these findings fit into the wider context of observations from other countries.

RESULTS

Asthma research in Ghana has focused mainly on children between the ages of 5-16 years with one published study that included adults. Different markers for the disease have been used such as clinician-diagnosed asthma, exercise-induced bronchospasm (EIB) as well as questionnaire-derived symptoms of asthma. Factors found to be associated with asthma in Ghana include atopic sensitisation to environmental allergens, inner-city residence and socioeconomic differences. Other implicated factors are family history of asthma, sib-ship position, breast-feeding duration and helminth infections.

CONCLUSIONS

Future research in Ghana must establish the burden of disease among all age-groups as well as clearly differentiate between allergic and non-allergic asthma. Studies are also needed to examine the role of environmental air pollutants on the disease's pathogenesis.

Socio-demographic disparities of childhood asthma

Childhood asthma is particularly prevalent among disadvantaged children and is associated with greater functional consequences. This study described factors associated with childhood asthma in a sample of Latino and non-Latino children. Data were from baseline measures of 791 parent and child dyads involved in a childhood obesity prevention study. Parents completed a self-administered survey assessing childhood factors, demographics, acculturation and child asthma diagnosis. Multivariate mixed effects logistic regression analyses tested for correlates of child asthma and ethnicity interactions. Children were 4-10 years old, half were female, 86.0 percent were US-born and 45.7 percent were overweight or obese. The prevalence of childhood asthma was 11.5 percent. In multivariate analyses, the odds of childhood asthma were greater among children of non-Latino descent (OR = 4.1, CI: 1.8, 9.2), who had health insurance (OR = 11.1, CI: 2.7, 46.4), were male (OR = 1.8; CI: 1.1, 3.1) and born pre-term (OR = 3.0, CI: 1.4, 6.3). This study supports socio-demographic disparities in childhood asthma and evidence of their independent effects.

Environmental epigenetics of asthma: an update

Asthma, a chronic inflammatory disorder of the airway, is influenced by interplay between genetic and environmental factors now known to be mediated by epigenetics. Aberrant DNA methylation, altered histone modifications, specific microRNA expression, and other chromatin alterations orchestrate a complex early-life reprogramming of immune T-cell response, dendritic cell function, macrophage activation, and a breach of airway epithelial barrier that dictates asthma risk and severity in later life. Adult-onset asthma is under analogous regulation. The sharp increase in asthma prevalence over the past 2 or 3 decades and the large variations among populations of similar racial/ethnic background but different environmental exposures favors a strong contribution of environmental factors. This review addresses the fundamental question of whether environmental influences on asthma risk, severity, and steroid resistance are partly due to differential epigenetic modulations. Current knowledge on the epigenetic effects of tobacco smoke, microbial allergens, oxidants, airborne particulate matter, diesel exhaust particles, polycyclic aromatic hydrocarbons, dietary methyl donors and other nutritional factors, and dust mites is discussed. Exciting findings have been generated by rapid technological advances and well-designed experimental and population studies. The discovery and validation of epigenetic biomarkers linked to exposure, asthma, or both might lead to better epigenotyping of risk, prognosis, treatment prediction, and development of novel therapies.

Effects of the indoor environment on the fraction of exhaled nitric oxide in school-aged children

BACKGROUND

The fractional concentration of exhaled nitric oxide (FeNO) appears to be a good marker for airway inflammation in children with asthma.

OBJECTIVE

To evaluate the effect of environmental exposures on exhaled nitric oxide in a community sample of children.

METHODS

The relationship among exhaled nitric oxide, underlying disease and home environmental exposures was examined using questionnaire data and measurement of exhaled nitric oxide in a cross-sectional study of 1135 children that included healthy children, and children with allergies and/or asthma who were attending grades 4 through 6 in Windsor, Ontario.

RESULTS

Among healthy children, there was a positive association between FeNO and occupancy (P<0.02). Compared with forced air and hot water radiant heat, electric baseboard heating was associated with a significant increase of FeNO in healthy children (P=0.007) and children with allergies (P=0.043). FeNO was not associated with environmental tobacco smoke exposure or reported surface mold. The presence of pet dog(s), but not cats, was associated with a significantly lower FeNO in healthy children (P<0.001) and in children with reported allergies (P<0.001).

CONCLUSIONS

The type of heating system, but not previously reported environmental tobacco smoke or mold exposure appears to affect exhaled nitric oxide in children. Exposure to different types of pets may have disparate effects on airway inflammation.

Why are some children with early onset of asthma getting better over the years?--diagnostic failure or salutogenetic factors

Among children earlier having been identified with a hospital or primary care diagnosis of asthma at least once between 0-7 years of age, almost 40 % of their parents reported in the ISAAC-questionnaire as never having had asthma (NA). These are further analysed and compared with the persisting asthma cases (A) in this study. All these children's medical records were scrutinized concerning their asthma diagnose retrospectively.The aim of this study was to analyse possible factors related to the outcome in an Asthma diagnosis reassessment by parental questionnaire at the age of ten of the children earlier having been identified with a hospital or primary health care diagnosis of asthma at least once between 0-7 years of age in a total birth-year cohort in a defined Swedish geographical area.A multiple logistic analysis revealed four significant and independent factors associated to the improvement/non-report of asthma at the age of ten. These factors were; not having any past experiences of allergic symptoms (p<0.0001), only having one or two visits at the hospital for asthma diagnosis in the 0-7 interval (p=0.001), not living in a flat but a villa at the age of ten (p=0.029) and no previous perception of mist or mould damage in the house (p=0.052).In the early postnatal stage, obstructive and bronchospastic symptoms typical of asthma may be unspecific, and those cases not continuing to persisting disease tend to have identifiable salutogenetic factors of constitutional rather than environmental nature, namely, an overall reduced allergic predisposition.

Point-counterpoint. The triumph of the null hypothesis: epidemiology in an age of change

The recent confusion concerning the relation between hormone replacement therapy and cardiovascular disease has stirred a new wave of debate about the value and future of epidemiology. Opponents of epidemiology suggest an ever-diminishing role in an age of small risks and complex diseases, yet proponents are not in consensus about how to adapt their discipline to the challenges associated with ageing societies and changing disease patterns. While epidemiology is likely to be increasingly called upon to make sense of the risks involved with these changes, wading into this era with a mindset and tools that were derived from epidemiology's 'golden era' of tackling major risk factors, has created more confusion than understanding. Increasingly, we need to downsize epidemiology to what is testable, measurable, and relevant, based on robust methodology and public health rationale. Applying an evolutionary perspective, that views health problems of modernity as a manifestation of the mismatch between our ancient genes and hi-tech lifestyles, can provide guidance for a 21st century research agenda.

Helicobacter pylori-infection status and childhood living conditions are associated with signs of allergic diseases in an occupational population

This study assessed the hypothesis that Helicobacter pylori infection and specific living conditions in childhood are associated with allergic outcomes. A cross-sectional survey containing retrospective questions concerning childhood was performed in an occupational population in 2001. This survey included self-administered questionnaire data and stool tests. An inverse association between positive H. pylori infection status and physician diagnosis of allergy/12 month period of anti-allergic medication was observed in a logistic regression model, adjusted for potential confounders (age, sex, nationality, smoking status and education of the participant) (OR 0.26, 95% CI: 0.08-0.84). In addition, childhood living conditions were associated with H. pylori infection status and signs of allergies. In line with the "hygiene hypothesis" our model supports an inverse association between early childhood infection with H. pylori and allergic disease in adulthood.

Childhood obesity: are we missing the big picture?

Childhood obesity is increasing worldwide, raising alarm about future trends of cardiovascular disease, diabetes and cancer. This article discusses what may underlie our failure to respond effectively to the obesity epidemic, and presents a wider perspective for future research and public health agendas. So far targeting individual-level determinants and clinical aspects of childhood obesity has produced limited success. There is growing interest in understanding the wider determinants of obesity such as the built environment (e.g. walkability), social interactions, food marketing and prices, but much needs to be learned. Particularly, we need to identify distal modifiable factors with multiple potential that would make them attractive for people and policymakers alike. For example, walking-biking-friendly cities can reduce obesity as well as energy consumption, air pollution and traffic delays. Such agenda needs to be driven by strong evidence from research involving multi-level influences on behaviour, as well as the study of wider politico-economic trends affecting people's choices. This article highlights available evidence and arguments for research and policy needed to curb the obesity epidemic. The upstream approach underlying these arguments aims to make healthy choices not only the most rational, but also the most feasible and affordable.

Increasing body mass index from age 5 to 14 years predicts asthma among adolescents: evidence from a birth cohort study

BACKGROUND

Obesity and asthma are common disorders, and the prevalence of both has increased in recent decades. It has been suggested that increases in the prevalence of obesity might in part explain the increase in asthma prevalence. This study aims to examine the prospective association between change in body mass index (BMI) z-score between ages 5 and 14 years and asthma symptoms at 14 years.

METHODS

Data was taken from the Mater University Study of Pregnancy and its outcomes (MUSP), a birth cohort of 7223 mothers and children started in Brisbane (Australia) in 1981. BMI was measured at age 5 and 14 years. Asthma was assessed from maternal reports of symptoms at age 5 and 14 years. In this study analyses were conducted on 2911 participants who had information on BMI and asthma at both ages.

RESULTS

BMI z-score at age 14 and the change in BMI z-score from age 5 to 14-years were positively associated with asthma symptoms at age 14 years, whereas BMI z-score at age 5 was not associated with asthma at age 14. Adjustment for a range of early-life exposures did not substantially alter these findings. The association between change in BMI z-score with asthma symptoms at 14 years appeared stronger for male subjects compared with female subjects but there was no statistical evidence for a sex difference (P=0.36).

CONCLUSIONS

Increase in BMI z-score between age 5 and 14 years is associated with increased risk of asthma symptoms in adolescence.

The environment and risk factors for atopy

Atopy is the genetic potential to manifest the trinity of classic allergic diseases--atopic dermatitis, allergic rhinitis, and asthma. All have been observed to have increased over the past several decades. The interplay of the genetics of atopy with various environmental exposures may manifest itself in the form of allergic phenotypes or paradoxically may actually suppress the allergic response. The hygiene hypothesis offers an explanation of why certain environmental exposures early in life may suppress or activate clinical disease. Primary prevention is directed at preventing the clinical manifestations of atopy by suppressing or delaying the onset of allergic sensitivity. Studies of primary prevention have brought mixed results. Secondary prevention is directed at reducing or removing triggers in the environment of the sensitized individual. Secondary prevention measures directed at one allergen have not proven successful. Comprehensive intervention programs dealing with both allergens and other potential triggers appear beneficial.

Another explanation for the low allergy rate in the rural Alpine foothills

A low allergy rate in coal and wood heated homes has been described in the small villages in the Alpine foothills and subsequently found to be associated with the farming environment. This was interpreted within the framework of the hygiene hypothesis but there are also alternative explanations. Lower air pollution could be one reason, which is, however, unlikely since the differences between the Bavarian countryside and the Munich municipal area were only weak. There could be genetic differences between the urban and rural population by previous isolation or by self-selection. The potential drop-out of allergy genes, however, will also not explain the absent increase of allergies in two generations. More likely, other lifestyle factors are important. Dietary habits are different in farmers and a less frequent vitamin D supplementation of newborns (otherwise expected to be allergy promoting) has been shown recently. The underlying cause for the "non-allergic farm child" remains speculative until the transfer of any farm-associated factor is leading to a similar risk reduction in the general population.