Association between the First Occurrence of Asthma and Residential Greenness in Children and Teenagers in Taiwan.

Chia-Jung Hsieh,Chun-Chieh Tseng,Rong-Hwa Jan,Pei-Ying Yu,Chun-Ju Tai,Tzai-Hung Wen,Shyang-Woei Lin

doi:10.3390/ijerph16122076

Abstract

Green spaces have benefits but may also increase the risk of allergic disease. This study examined the association between the first occurrence of asthma and greenness exposure in children and teenagers. We conducted a 1:1 matched case-control study matched by sex, age, and the first diagnosis year with 7040 eligible subjects from a systematic sampling cohort database in Taiwan from 2001 to 2013. A normalized difference vegetation index (NDVI) value ≥0.4 was used as the criterion to determine the green space. The green cover images were then transformed to the green coverage rate in the township surrounding the residential areas of the asthma and control subjects. Conditional logistic regression analyses demonstrated that a significantly increased risk of asthma in preschool children was associated with the surrounding greenness after adjusting for urbanization level, frequency of healthcare provider visits, mean township family income, CO, NOx, and PM2.5. The risk of asthma occurrence increased significantly with increasing greenness exposure (p-trend < 0.05). Nevertheless, exposure to the highest greenness levels (81–100%) was not associated with a significantly higher risk of asthma occurrence than was exposure to the lowest values (0–20%) of greenness. This study suggests that green space design should consider more effective methods of reducing the allergy impact.

Highlights

Asthma is the most prevalent childhood chronic airway disease
Our findings suggest that the effect of green coverage on asthma occurrence is neither absolutely positive nor negative
This study demonstrates that the risk of a first asthma occurrence is significantly associated with higher levels of greenness exposure in preschool children

Summary

Introduction

Asthma is the most prevalent childhood chronic airway disease. In Taiwan, the prevalence of asthma is 5.1% in the general population; the prevalence rate can be twice that percentage or even higher in children [1]. The main etiology of asthma in children is not fully understood and still needs clarification. With regard to environmental risk factors, a variety of allergens such as pollens, molds, and dust mites can trigger asthma [2]. Several studies have indicated that the increasing asthma prevalence is associated with urban air pollutants, especially long-term exposure to carbon monoxide (CO) [3], nitrogen oxides (NOx ) [3,4], and particulate matter 2.5 (PM2.5 ) [5]. Green environments are often associated with benefits such as reducing heat, noise, and air pollution exposure [6]; exposure to greenness may induce some

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