Residential environmental risk factors for childhood asthma prevalence in metropolitan and semirural cities in Korea

Housing typologies and asthma: a scoping review

Asthma is related to triggers within the home. Although it is recognised that triggers likely occur due to characteristics of housing, these characteristics have not been comprehensively reviewed, and there is a paucity of housing-focused interventions to reduce asthma and asthma symptoms. Following five steps identified by Arksey and O'Malley, we conducted a scoping review of published evidence on the associations between asthma and housing characteristics. We searched three electronic databases (PubMed, Scopus, Web of Science), identifying 33 studies that met our inclusion criteria. Through an iterative approach, we identified nine housing characteristics relevant to asthma onset or exacerbation, categorised as relating to the surrounding environment (location), the house itself (dwelling), or to conditions inside the home (occupancy). We conceptualise these three levels through a housing typologies framework. This facilitates the mapping of housing characteristics, and visualises how they can cluster and overlap to exacerbate asthma or asthma symptoms. Of the three levels in our framework, associations between asthma and locational features were evidenced most clearly in the literature reviewed. Within this category, environmental pollutants (and particularly air pollutants) were identified as a potentially important risk factor for asthma. Studies concerning associations between dwelling features and occupancy features and asthma reported inconsistent results, highlighting the need for greater research in these areas. Interpreting housing-related asthma triggers through this framework paves the way for the identification and targeting of typologies of housing that might adversely affect asthma, thus addressing multiple characteristics in tandem rather than as isolated elements.

Risk factors of asthma in the Asian population: a systematic review and meta-analysis

Background and objective

An increasing trend of asthma prevalence was observed in Asia; however, contributions of environmental and host-related risk factors to the development of this disease remain uncertain. This study aimed to perform a systematic review and meta-analysis for asthma-associated risk factors reported in Asia.

Methods

We systematically searched three public databases (Web of Science, PubMed, and Scopus) in Feb 2021. We only included articles that reported environmental and host-related risk factors associated with asthma in the Asian population. Random-effect meta-analyses were conducted for frequently reported asthma-associated risk factors to provide an overall risk estimate of asthma development.

Results

Of 4030 records obtained from public databases, 289 articles were selected for review. The most frequently reported asthma-associated risk factor was the family history of allergy-related conditions. The random-effect asthma risk estimates (pooled odds ratio, OR) were 4.66 (95% confidence interval (CI): 3.73–5.82) for the family history of asthma, 3.50 (95% CI: 2.62–4.67) for the family history of atopy, 3.57 (95% CI: 3.03–4.22) for the family history of any allergic diseases, 1.96 (95% CI: 1.47–2.61) for the family history of allergic rhinitis, and 2.75 (95% CI: 1.12–6.76) for the family history of atopic dermatitis. For housing-related factors, including the presence of mold, mold spots, mold odor, cockroach, water damage, and incense burning, the random-effect pooled OR ranged from 1.43 to 1.73. Other risk factors with significant pooled OR for asthma development included male gender (1.30, 95% CI: 1.23–1.38), cigarette smoke exposure (1.44, 95% CI: 1.30–1.60), cigarette smoking (1.66, 95% CI: 1.44–1.90), body mass index (BMI)–related parameters (pooled OR ranged from 1.06 to 2.02), various types of air pollution (NO₂, PM10, and O₃; pooled OR ranged from 1.03 to 1.22), and pre- and perinatal factors (low birth weight, preterm birth, and cesarean section; pooled OR ranged from 1.14 to 1.32).

Conclusions

The family history of asthma was the most frequently reported risk factor for asthma development in Asia with the highest risk estimate for asthma development. This suggests a major role of the genetic component in asthma pathogenesis. Further study on asthma genetics is required to improve the current understanding of asthma etiology.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40101-021-00273-x.

Trends in the Prevalence of Childhood Asthma in Seoul Metropolitan City, Korea: The Seoul Atopy ∙ Asthma-friendly School Project

Objectives

The project Seoul Atopy ∙ Asthma-friendly School investigated the current status of childhood asthma to enable formulation of a preventative policy. We evaluated the current prevalence of childhood asthma in Seoul and its trends and related factors.

Methods

The project was conducted annually from 2011 to 2016 and involved around 35 000 children aged 1-13 years. Based on the International Study of Asthma and Allergies in Childhood guidelines, the survey involved parents. The associations of the particulate matter (PM₁₀) concentration, and the number of days on which the daily air quality guidance level was exceeded in the 25 districts of Seoul, with the prevalence of asthma were assessed.

Results

The age-standardized asthma prevalence in 2011 and 2016 was 6.74 and 4.02%, respectively. The prevalence of lifetime asthma treatment and treatment during the last 12 months tended to decrease from 2011 to 2016. Asthma treatment was significantly correlated with the number of days on which the daily air quality guidance level was exceeded, but not with the PM₁₀ concentration.

Conclusions

This study reports the prevalence of asthma among children in Seoul and confirmed the relationship between childhood asthma and known risk factors in a large-scale survey.

Time trends of the prevalence of allergic diseases in Korea: A systematic literature review

The prevalence of allergic diseases has increased dramatically in recent decades, and are now considered major chronic diseases at the global level. The increasing burden of allergic diseases has led to numerous worldwide and local researchers to investigate the time trends in its prevalence and identify its driving factors. Environmental changes such as urbanization and industrialization have been suggested to explain the increasing prevalence, but recent reports from Western countries suggest that this prevalence has reached a plateau or even possibly, started to decrease. However, such environmental changes are still occurring in many Asia-Pacific countries, including Korea, and it is speculated that the peak in allergy epidemics has yet to come. The present systematic literature review aimed to explore the time trends in the prevalence of allergic diseases in Korea and to identify the unmet needs for facilitating further studies.

Does urban extent from satellite images relate to symptoms of asthma, rhinoconjunctivitis and eczema in children? A cross-sectional study from ISAAC Phase Three

OBJECTIVE

The relationship between urbanisation and the symptom prevalence of asthma, rhinoconjunctivitis and eczema is not clear, and varying definitions of urban extent have been used. Furthermore, a global analysis has not been undertaken. This study aimed to determine whether the symptom prevalence of asthma, rhinoconjunctivitis and eczema in centres involved in the International Study of Asthma and Allergies in Childhood (ISAAC) were higher in urban than rural centres, using a definition of urban extent as land cover from satellite data.

METHODS

A global map of urban extent from satellite images (MOD500 map) was used to define the urban extent criterion. Maps from the ISAAC centres were digitised and merged with the MOD500 map to describe the urban percentage of each centre. We investigated the association between the symptom prevalence of asthma, rhinoconjunctivitis and eczema and the percentage of urban extent by centre.

RESULTS

A weak negative relationship was found between the percentage of urban extent of each ISAAC centre and current wheeze in the 13-14-year age group. This association was not statistically significant after adjusting for region of the world and gross national income. No other relationship was found between urban extent and symptoms of asthma, rhinoconjunctivitis and eczema.

CONCLUSIONS

In this study, the prevalence of symptoms of asthma, rhinoconjunctivitis and eczema in children were not associated with urbanisation, according to the land cover definition of urban extent from satellite data. Comparable standardised definitions of urbanisation need to be developed so that global comparisons can be made.

Socioeconomic and sociodemographic factors related to allergic diseases in Korean adolescents based on the Seventh Korea Youth Risk Behavior Web-based Survey: a cross-sectional study

Background

Various international reports have shown that socioeconomic and sociodemographic variables are correlated with allergic diseases; however, little is known about how these variables affect Korean adolescents. This study was conducted to identify socioeconomic and sociodemographic risk factors for allergic diseases in Korean adolescents to provide information for preventing and managing such conditions.

Methods

Data from the 2011 Korea Youth Risk Behavior Web-based Survey (KYRBWS-VII) of 75,643 adolescents were used. An anonymously administered online survey was conducted to collect dependent variable information on perceived sexes, residence, family affluence (Family Affluence Scale; FAS), parental education levels, subjective academic achievement, obesity, drinking and smoking. The independent variables were asthma, allergic rhinitis and atopic dermatitis. Multivariate logistic regression was used to analyze the correlations between the dependent and independent variables.

Results

Low subjective academic achievement, obesity, drinking and smoking were risk factors for asthma. High FAS, parental bachelor’s degree and high subjective academic achievement were risk factors for allergic rhinitis. Finally, high FAS, maternal bachelor’s degree and high subjective academic achievement were risk factors for atopic dermatitis.

Conclusion

We found that high socioeconomic status (SES) was a risk factor for allergic diseases in Korean adolescents. We propose that the greater access to medical services and immunization (e.g., hygiene hypothesis) afforded by high SES influenced the prevalence of allergic diseases. Thus, as the Korean economy develops further, the prevalence of allergic diseases is likely to increase. Controlling harmful behavioral risk factors, such as drinking and smoking, may help to prevent adolescent allergic diseases.

Operational definitions of asthma in recent epidemiological studies are inconsistent

OBJECTIVE

The best combination of questions to define asthma in epidemiological asthma studies is not known. We summarized the operational definitions of asthma used in prevalence studies and empirically assess how asthma prevalence estimates vary depending on the definition used.

METHODS

We searched the Thomson Reuters ISI Web of knowledge and included (1) cross-sectional studies (2) on asthma prevalence (3) conducted in the general population and (4) containing an explicit definition of asthma. The search was limited to the 100 most-cited papers or published since January 2010. For each paper, we recorded the asthma definition used and other variables. Then we applied the definitions to the data of the Portuguese National Asthma survey (INAsma) and of the 2005-2006 National Health and Nutrition Examination Survey (NHANES) computing asthma prevalence estimates for the different definitions.

RESULTS

Of 1738 papers retrieved, 117 were included for analysis. Lifetime asthma, diagnosed asthma and current asthma were defined in 8, 12 and 29 different ways, respectively. By applying definitions of current asthma on INAsma and NHANES data, the prevalence ranged between 5.3%-24.4% and 1.1%-17.2%, respectively.

CONCLUSIONS

There is considerable heterogeneity in the definitions of asthma used in epidemiological studies leading to highly variable estimates of asthma prevalence. Studies to inform a standardized operational definition are needed. Meanwhile, we propose a set of questions to be reported when defining asthma in epidemiological studies.

Minimal difference in the prevalence of asthma in the urban and rural environment

Multiple risk factors can be modified to decrease asthma incidence. It is important to understand early risks to decrease exposure to harmful conditions in the environment that can trigger asthma which may not be clinically evident in children until they reach adulthood. A retrospective literature review of articles on the prevalence of asthma in the urban versus rural environment was initiated in order to understand the effect of the environment on asthma. The urban-living effect is a global problem in the face of growing population, industrialization and pollution. The socioeconomic dichotomy in the urban versus rural environment also affects access and quality of health care.

Articles reviewed had differences in the urban versus rural prevalence of asthma. However, further analysis of specific risk factors and socioeconomic trends that increased susceptibility to asthma was the same in these studies. Some rural areas may have similar environmental and socioeconomic issues that place them at the same risk for the development of asthma as their urban counterparts.

Urban locations generally tend to have the prototype environment that can lead to the predisposition of asthma. Ultimately, the incidence of asthma can be decreased if these environmental and socioeconomic issues are addressed. However, every effort is needed from the level of the individual to the community at large.

A GIS-based assessment of environmental influences on allergy development in children

This study aims to assess potential environmental influences on allergy development in children. Based on a parent-completed questionnaire survey administered in Hong Kong in 2003 in accordance with the International Study of Asthma and Allergies in Childhood protocol, the prevalence and incidence of asthma and rhinoconjunctivitis of 508 preschool children aged 4 to 6 years in Yuen Long District were determined and a range of indoor and outdoor environmental factors were assessed. Exposure to moisture and mold in the first year of life increased the risk of asthma (adjusted odds ratio [aOR] = 2.56; 95% confidence interval [CI] = 1.40-4.68) and rhinoconjunctivitis (aOR = 2.09; 95% CI = 1.15-3.80). Current maternal smoking was also associated with a higher prevalence of asthma (aOR = 2.00; 95% CI = 1.04-3.84). No association was observed between outdoor traffic-related air pollutants and the prevalence of the allergic conditions. Indoor home environments had a stronger influence on allergy development, whereas exposure to traffic-related external environment gave a variable effect, the significance of which would be difficult to be substantiated.