Winter Season Temperature Drops and Sulfur Dioxide Levels Affect on Exacerbation of Refractory Asthma in South Korea: A Time-Trend Controlled Case-Crossover Study Using Soonchunhyang Asthma Cohort Data

Association between cold weather, influenza infection, and asthma exacerbation in adults in Hong Kong

Despite a conspicuous exacerbation of asthma among patients hospitalized due to influenza infection, no study has attempted previously to elucidate the relationship between environmental factors, influenza activity, and asthma simultaneously in adults. In this study, we examined this relationship using population-based hospitalization records over 22 years. Daily numbers of hospitalizations due to asthma in adults of 41 public hospitals in Hong Kong during 1998-2019 were obtained. The data were matched with meteorological records and air pollutant concentrations. We used type-specific and all-type influenza-like illness plus (ILI+) rates as proxies for seasonal influenza activity. Quasi-Poisson generalized additive models together with distributed-lag non-linear models were used to examine the association. A total of 212,075 hospitalization episodes due to asthma were reported over 22 years. The cumulative adjusted relative risk (ARR) of asthma hospitalizations reached 1.15 (95 % confidence interval [CI], 1.12-1.18) when the ILI+ total rate increased from zero to 20.01 per 1000 consultations. Compared with the median temperature, a significantly increased risk of asthma hospitalization (cumulative ARR = 1.10, 95 % CI, 1.05-1.15) was observed at the 5^th percentile of temperature (i.e., 14.6 °C). Of the air pollutants, oxidant gas was significantly associated with asthma, but only at its extreme level of concentrations. In conclusion, cold conditions and influenza activities are risk factors to asthma exacerbation in adult population. Influenza-related asthma exacerbation that appeared to be more common in the warm and hot season, is likely to be attributable to influenza A/H3N2. The heavy influence of both determinants on asthma activity implies that climate change may complicate the asthma burden.

Seasonal differences in the effects of local concentrations of atmospheric substances and meteorological elements on asthma exacerbation of children in metropolitan area, Korea: A 13-year retrospective single-center study

Purpose

Air pollutants contribute to asthma exacerbation, and the types of air pollutants involved in acute asthma exacerbation may differ depending on climate and environmental conditions. This study aimed to identify factors affecting asthma exacerbation in each of the four seasons so that to prevent acute asthma exacerbation and to establish effective treatment strategies for each season.

Methods

Pediatric patients aged 0-18 years old hospitalized or admitted to the emergency room for asthma exacerbation at Hanyang University Guri Hospital between January 1, 2007, and December 31, 2019 were recruited. The number of asthma exacerbations comprised the total number of patients admitted to the emergency room or hospitalized for asthma and treated with systemic steroids. The association between the number of asthma exacerbations/week and average concentrations of atmospheric substances and meteorological elements in that week were analyzed. Multiple linear regression analyses were performed to examine the association between various atmospheric variables and the number of asthma exacerbations.

Results

The number of asthma exacerbations was found to be associated with the concentration of particulate matter with an aerodynamic diameter of ≤10 μm in that week in autumn. No atmospheric variables exhibited an association in other seasons.

Conclusions

Air pollutants and meteorological factors affecting asthma exacerbation vary by season. Moreover, their effects may change via their interaction with each other. The results of this study suggest that it will be helpful to establish differentiated measures for each season to prevent asthma exacerbation.

Association between ambient sulfur dioxide pollution and asthma mortality: Evidence from a nationwide analysis in China

There is a lack of research on the effects of acute exposure to ambient sulfur dioxide (SO2) on mortality caused by asthma, especially nationwide research in China. To explore the acute effect of exposure to ambient SO2 on asthma mortality using nationwide dataset in China from 2015 to 2020 and further evaluate the associations in subgroups with different geographical and demographic characteristics. We used data from China's Disease Surveillance Points system with 29,553 asthma deaths in China during 2015-2020. The exposure variable was the daily mean concentrations of SO2 from the ChinaHighSO2 10 km × 10 km daily grid dataset. Bilinear interpolation was used to estimate each individual's exposure to air pollutants and meteorological variables. We used a time-stratified case crossover design at the individual level to analyze the exposure response relationship between short-term exposure to SO2 and asthma mortality. Stratified analyses were carried out by sex, age group, marital status, warm season and cold season, urbanicity and region. Significant associations between short-term exposure to ambient SO2 and increased asthma mortality were found in this nationwide study. The excess risk (ER) for each 10 μg/m3 increase in SO2 concentrations at lag07 was 7.78 % (95 % CI, 4.16-11.52 %). Season appeared to significantly modify the association. The associations were stronger in cold season (ER 9.78 %, 95 % CI:5.82 -13.89 %). The association remained consistent using different lag periods, adjusting for other pollutants, and in the analysis during pre-Corona Virus Disease 2019 (COVID-19) period. Our study indicates increased risk of asthma mortality with acute exposures to SO2 in Chinese population. The current study lends support for greater awareness of the harmful effect of SO2 in China and other countries with high SO2 pollution.

Cold temperature and sudden temperature drop as novel risk factors of asthma exacerbation: a longitudinal study in 18 Chinese cities

BACKGROUND

Few studies have explored the role of ambient temperature in asthma exacerbation.

OBJECTIVE

We aimed to explore the association of temperature with diurnal peak expiratory flow (PEF) variation and asthma exacerbation.

METHOD

We developed a longitudinal study among asthmatic adults in 18 Chinese cities. Subjects recorded PEF in dynamic pulmonary function monitoring from 2017 to 2020. Linear mixed-effect model and generalized additive model with distributed non-linear models were used to assess the effect of temperature and temperature change between neighboring days (TCN) on diurnal PEF variation and the risk of asthma exacerbation.

RESULT

We evaluated a total of 79,217 daily PEF monitoring records from 4467 adult asthmatic patients. There were significant increase of diurnal PEF variation and higher risk of asthma exacerbation with cold and sudden temperature drop. Compared with the referent temperature (99th percentile, 32 °C), exposure to moderate cold (25th percentile, 3 °C) and extreme cold (2.5th percentile, -7 °C) was associated with elevations of 1.28% and 1.16% in diurnal PEF variation over lag 0-2 days, respectively. The odds ratios of asthma exacerbation (determined by diurnal PEF variation >20%) at the two temperature cutoffs were 1.68 and 1.73. A sudden temperature drop (2.5th percentile of TCN, -5 °C) was associated with 1.13% elevation in diurnal PEF variation, and with increased risk of asthma exacerbation (odd ratio = 1.50) over lag 0-4 days.

CONCLUSION

This large multicenter study provided the first-hand empirical evidence that cold temperature and a temperature drop may increase the risk of asthma exacerbation.

Systemic Disorders Closely Associated with Malocclusion in Late Adolescence: A Review and Perspective

Oral diseases such as dental caries and periodontal disease are reported to be associated with various systemic diseases such as heart disease, respiratory disease, diabetes, rheumatism, and metabolic syndrome, thus increasing the importance of prevention and early treatment [...].

Outdoor air pollution and the risk of asthma exacerbations in single lag0 and lag1 exposure patterns: a systematic review and meta-analysis

Objective: To synthesize evidence regarding the relationship between outdoor air pollution and risk of asthma exacerbations in single lag0 and lag1 exposure patterns.Methods: We performed a systematic literature search using PubMed, Embase, Cochrane Library, Web of Science, ClinicalTrials, China National Knowledge Internet, Chinese BioMedical, and Wanfang databases. Articles published until August 1, 2020 and the reference lists of the relevant articles were reviewed. Two authors independently evaluated the eligible articles and performed structured extraction of the relevant information. Pooled relative risks (RRs) and 95% confidence intervals (CIs) of lag0 and lag1 exposure patterns were estimated using random-effect models.Results: Eighty-four studies met the eligibility criteria and provided sufficient information for meta-analysis. Outdoor air pollutants were associated with increased risk of asthma exacerbations in both single lag0 and lag1 exposure patterns [lag0: RR (95% CI) (pollutants), 1.057(1.011, 1.103) (air quality index, AQI), 1.007 (1.005, 1.010) (particulate matter of diameter ≤ 2.5 μm, PM_2.5), 1.009 (1.005, 1.012) (particulate matter of diameter, PM₁₀), 1.010 (1.006, 1.014) (NO₂), 1.030 (1.011, 1.048) (CO), 1.005 (1.002, 1.009) (O₃); lag1:1.064(1.022, 1.106) (AQI), 1.005 (1.002, 1.008) (PM_2.5), 1.007 (1.004, 1.011) (PM₁₀), 1.008 (1.004, 1.012) (NO₂), 1.025 (1.007, 1.042) (CO), 1.010 (1.006, 1.013) (O₃)], except SO₂ [lag0: RR (95% CI), 1.004 (1.000, 1.007); lag1: RR (95% CI), 1.003 (0.999, 1.006)]. Subgroup analyses revealed stronger effects in children and asthma exacerbations associated with other events (including symptoms, lung function changes, and medication use).Conclusion: Outdoor air pollution increases the asthma exacerbation risk in single lag0 and lag1 exposure patterns.Trial registration: PROSPERO, CRD42020204097. https://www.crd.york.ac.uk/.Supplemental data for this article is available online at https://doi.org/10.1080/02770903.2021.2008429 .

Effects of air temperature on the number of ambulance calls for asthma during cold season in Nur-Sultan- the second coldest capital in the world

Deleterious effect of cold on overall mortality is well-established. We studied associations between the air temperature and the number f ambulance calls for asthma in Nur-Sultan, Kazakhstan – the second coldest capital in the world. Daily counts of ambulance calls for asthma in Nur-Sultan for the cold seasons (October-March) 2006–2010 were obtained from the Municipal Ambulance Station. Associations between the number of calls and mean and minimum apparent temperatures (average for lags 0–15) were studied using first-order Poisson auto-regression models controlling for wind speed and effects of month, year, weekends and holidays. Altogether, there were 7373 ambulance calls for asthma during the study period. An inverse association between minimum apparent temperature and the number of calls was observed for the age-group 60 years and older. A decrease of the minimum apparent temperature by 1°C was associated with an increase in the number of calls by 1.7% (95% CI: 0.1%-3.3%) across the whole temperature spectrum. No associations in other age groups were found. Our results suggest an inverse association between the average 15-day lag minimum apparent temperature and the number of ambulance calls during the cold season in Nur-Sultan, but this is limited to the oldest age-group.

Effects of Air Pollutants on Airway Diseases

Air pollutants include toxic particles and gases emitted in large quantities from many different combustible materials. They also include particulate matter (PM) and ozone, and biological contaminants, such as viruses and bacteria, which can penetrate the human airway and reach the bloodstream, triggering airway inflammation, dysfunction, and fibrosis. Pollutants that accumulate in the lungs exacerbate symptoms of respiratory diseases such as asthma and chronic obstructive pulmonary disease (COPD). Asthma, a heterogeneous disease with complex pathological mechanisms, is characterized by particular symptoms such as shortness of breath, a tight chest, coughing, and wheezing. Patients with COPD often experience exacerbations and worsening of symptoms, which may result in hospitalization and disease progression. PM varies in terms of composition, and can include solid and liquid particles of various sizes. PM concentrations are higher in urban areas. Ozone is one of the most toxic photochemical air pollutants. In general, air pollution decreases quality of life and life expectancy. It exacerbates acute and chronic respiratory symptoms in patients with chronic airway diseases, and increases the morbidity and risk of hospitalization associated with respiratory diseases. However, the mechanisms underlying these effects remain unclear. Therefore, we reviewed the impact of air pollutants on airway diseases such as asthma and COPD, focusing on their underlying mechanisms.

Climatic factors are associated with asthma prevalence: An ecological study using English quality outcomes framework general practitioner practice data

Asthma is a complex disease with multiple environmental factors proposed to contribute to aetiology. Geographical analyses can shed light on the determinants of asthma. Ultraviolet radiation has been associated with asthma prevalence in past ecological studies. We have increased the detail of examining the association between asthma and ultraviolet radiation with addition of the variables of temperature, relative humidity and precipitation. An ecological study was designed to investigate meteorological factors associated with asthma prevalence in England. Data from the 2005 quality outcomes framework were used to determine the prevalence of asthma in primary care in England. This information was supplemented with indicators of obesity and smoking of the General Practitioner practice and population (by age and sex), deprivation and ethnicity at lower super output level from the 2001 and 2011 census. Annual mean meteorological data was attained from the Met Office and Joint Research Centre. We used a multiple linear regression to examine individual and multiple climatic factors through a principal components analysis. We tested for an association with asthma prevalence, after taking into account the spatial autocorrelation of the data. Asthma prevalence from general practice surgeries in England was 5.88% (95% CI 5.83 to 5.92). In the highest ultraviolet radiation weighted by the pre-vitamin D action spectrum (UV_vitd) quartile (2.12 to 2.50 kJ/m²/day), asthma had a 5% reduction in prevalence; compared to the lowest quartile here (0.95 (95% CI 0.92 to 0.98)). Similar reductions were found in the higher temperature 0.93 (95% CI 0.90 to 96). The opposite was found with relative humidity 1.09 (95% CI 1.05 to 1.12). A combination of high temperature and UVvitd highlighted postcode districts in the South East of England with a climate beneficial to low asthma prevalence. The South West of England represented a climate which had both beneficial and detrimental associations with asthma development. Climate is associated with asthma prevalence in England. Understanding the contribution of multiple climatic factors and the relationship with the indoor environment could help to explain the population distribution of asthma.

Temperature changes between neighboring days and childhood asthma: a seasonal analysis in Shanghai, China

Few evidences are available about the impact of temperature variation on childhood asthma in different seasons. This study aimed to assess the influence of temperature changes between neighboring days (TCN) on the exacerbation of asthma among children. Daily outpatient visits for childhood asthma (DOVCA) were collected from 17 main hospitals in Shanghai, China, from 2016 to 2018. A quasi-Poisson regression combined with distributed lagged nonlinear models was employed to estimate the association between TCN and asthma visits in cool or warm seasons, after controlling for short- and long-term trends, day of week, holidays, daily mean temperature, daily mean relative humidity, and air pollutants. The TCN varied from - 9.6 to 6.7 °C. The relationship between TCN and DOVCA greatly varied by season. In warm seasons, positive TCN (temperature rise) was associated with higher risks of asthma outpatient visits and negative TCN (temperature drop) was associated with lower risks; the associations were present on lag 1 day and lasted for 2 weeks; the cumulative relative risk of childhood asthma over 0 to 14 days was 1.98 (95% confidence interval: 1.42, 2.76) and 0.31 (95% confidence intervals: 0.21, 0.44) comparing a TCN of 2.5 °C (5th percentile) and - 3.2 °C (95th percentile) with 0 °C, respectively. In cool seasons, neither negative nor positive TCN showed significant risks. In conclusion, temperature rise might increase the risk of childhood asthma exacerbation and temperature drop might decrease the risks in warm seasons. There were no statistically significant influences in cool seasons.

A Multifactorial Evaluation of the Effects of Air Pollution and Meteorological Factors on Asthma Exacerbation

In the real world, dynamic changes in air pollutants and meteorological factors coexist simultaneously. Studies identifying the effects of individual pollutants on acute exacerbation (AE) of asthma may overlook the health effects of the overall combination. A comprehensive study examining the influence of air pollution and meteorological factors is required. Asthma AE data from emergency room visits were collected from the Taiwan National Health Insurance Research Database. Complete monitoring data for air pollutants (SO₂; NO₂; O₃; CO; PM_2.5; PM₁₀) and meteorological factors were collected from the Environmental Protection Agency monitoring stations. A bi-directional case-crossover analysis was used to investigate the effects of air pollution and meteorological factors on asthma AE. Among age group divisions, a 1 °C temperature increase was a protective factor for asthma ER visits with OR = 0.981 (95% CI, 0.971–0.991) and 0.985 (95% CI, 0.975–0.994) for pediatric and adult patients, respectively. Children, especially younger females, are more susceptible to asthma AE due to the effects of outdoor air pollution than adults. Meteorological factors are important modulators for asthma AE in both asthmatic children and adults. When studying the effects of air pollution on asthma AE, meteorological factors should be considered.

Effects of air pollution on moderate and severe asthma exacerbations

Background: Few studies have evaluated the impact of air pollution levels on the severity of exacerbations. Thus, we compared the relative risks posed by air pollutant levels on moderate and severe exacerbations.Methods: Exacerbation episodes of 618 from 143 adult asthmatics were retrospectively collected between 2005 and 2015 in a tertiary hospital of Korea. Air pollution GPS data for the location closest to each patient's home were obtained from the national ambient monitoring station. The relative impacts of air pollutants on asthma exacerbations were evaluated via a time-trend controlled symmetrical, bidirectional, case-crossover design using conditional logistic regression models on the day of the exacerbation (T-0) and up to 3 days before the exacerbation (T-1-T-3).Results: Overall asthma exacerbation were associated with O₃ levels in summer and winter (OR: 1.012[1.003-1.02] and 1.009[1.003-1.016]), SO₂ levels in spring and summer (OR: 1.009[1-1.018] and 1.02[1.006-1.035]) and NO₂ levels in winter (OR: 1.007[1.003-1.011]). Analyses of the temporal relationship between O₃ concentrations and exacerbations demonstrated that 63.2% of episodes in the summer occurred when the O₃ concentrations on T-1 were significantly higher than those on control days, while 51% of exacerbation episodes in the winter occurred. Severe and moderate exacerbations were similarly associated with O₃ levels in winter (OR: 1.012 [1.003-1.02] vs. 1.01 [0.999-1.021], p > 0.05) and in summer (OR: 1.006 [1.002-1.009] vs. 1.009 [1.003-1.016], p > 0.05).Conclusions: Asthma exacerbations may be associated with the seasonal elevation of O₃, SO₂ and NO₂ levels in summer and winter with the similar relative risk between moderate and severe exacerbations.

The association between pollutant levels and asthma-related emergency department visits in the Bronx after the World Trade Center attacks

Objective: To examine the potential impact of the World Trade Center (WTC) attacks on asthma-related emergency department visits (AREDV) in the New York City borough of the Bronx. Methods: We obtained daily nitrogen dioxide (NO₂), sulfur dioxide (SO₂) and ozone (O₃) values from the National Climatic Data Center's collection station in the Bronx from 1999 and 2002, a year before and after the WTC attacks. We compared daily AREDV and pollutant levels between 1999 and 2002 using the Wilcoxon signed rank sum test. We considered each season separately due to seasonal variations of AREDV and pollutants. We then used multiple linear regression models to assess the relationships between the changes in AREDV and the changes in pollutants from 1999 to 2002 in each season. Results: There were statistically significant increases from 1999 to 2002 in the daily NO₂ in the summer. Significant increases for daily SO₂ and O₃ values from 1999 to 2002 occurred in all seasons. Significant increases occurred in daily AREDV values in the spring and fall. Multiple linear regression analyses showed that increases in the daily O₃ values were significantly associated with increases in AREDV from 1999 to 2002 in the summer season. Conclusion: We observed a possible association between the WTC attacks and significant increases in O₃ and SO₂ for all seasons, and NO₂ for the summer. AREDV significantly increased following the WTC attacks. Increases in daily O₃ values were significantly associated with increases in AREDV in the summer season.

Association between the Ratio of FEV₁ to FVC and the Exposure Level to Air Pollution in Neversmoking Adult Refractory Asthmatics Using Data Clustered by Patient in the Soonchunhyang Asthma Cohort Database

Using real-world cases, asthma-related clinical data were clustered by patient; 5% of all asthmatics were found to have refractory asthma (RA) with a relatively low lung function (forced expiratory volume in 1 s/forced vital capacity (FEV₁/FVC) less than 80%). Using a multilevel study design for clustered spirometry data observed between 2005 and 2014, we evaluated the association between changes in the ratio of FEV₁ to FVC and variations in acute exposure to air pollution. We analyzed 2310 episodes of RA from 214 neversmoking patients. In spring, a 1 µg/m³ increase in concentration of particles ≤10 μm (PM10) on Lag 1 significantly reduced the ratio by 0.4% (95% confidence interval (CI): 0.1⁻0.7%) after adjusting for sex, age, body mass index (BMI), and total Immunoglobulin E (IgE) level. Unit (ppb) increase in SO₂ concentration on Lag 3 and 4 in fall and on Lag 6 in winter significantly reduced the ratio by 2 to 3% (p < 0.05). We found that acute exposure to PM10 in spring or SO₂ in fall or winter were positively associated with lung function drop indicating necessity of control strategies of target air pollutant source by season to protect susceptible population.

Temperature drop and the risk of asthma: a systematic review and meta-analysis

The relationship between asthma and temperature changes remains controversial. The aim of this study was to investigate the association between temperature changes and the risk of asthma. A total of 26 studies (combined total number of subjects N > 26 million), covering 13 countries and Costa Rica, were identified by using a series of keywords in different combinations and searching the papers in PubMed, EMBSEA, Web of Science, MEDLINE, AIM, LILACS, and WPRIM before February 2016. Most of the papers were published in English. Random-effects meta-analyses were performed to evaluate the effect of temperature drop on risk of asthma. Several secondary analyses were also calculated based on stratification for different age, season, latitude, and region on risk of asthma. The odds ratio (OR) estimate between temperature drop and asthma was 1.05 (95% CI 1.02, 1.08) in the meta-analysis. For children, the overall OR was 1.09 (95% CI 1.03, 1.15). Dose-effect analyses showed stronger associations in asthma risk for each 1°1 °C decrement in short-term temperature (OR 1.055, 95% CI 1.00, 1.11). Further stratifications showed that winter (OR 1.03, 95% CI 1.01, 105) and low latitude (OR 1.72, 95% CI 1.23, 2.41) have a statistically significant association with the increased risk of asthma. Exposure of people to short-term temperature drop (per 1 °C decrement) was significantly associated with the risk of lower respiratory tract infections (LRTI) with asthma (OR 1.02, 95% CI 1.00, 1.04). Results suggest an adverse effect of temperature drop on asthma risk, especially in children and low-latitude areas. It may be opportune to consider the preventive actions against temperature drop, including simple face masks, to decrease the risk of asthma.

Urban air pollution and meteorological factors affect emergency department visits of elderly patients with chronic obstructive pulmonary disease in Taiwan

Both air pollution and meteorological factors in metropolitan areas increased emergency department (ED) visits from people with chronic obstructive pulmonary disease (COPD). Few studies investigated the associations between air pollution, meteorological factors, and COPD-related health disorders in Asian countries. This study aimed to investigate the relationship between the environmental factors and COPD-associated ED visits of susceptible elderly population in the largest Taiwanese metropolitan area (Taipei area, including Taipei city and New Taipei city) between 2000 and 2013. Data of air pollutant concentrations (PM₁₀, PM_2.5, O₃, SO₂, NO₂ and CO), meteorological factors (daily temperature, relative humidity and air pressure), and daily COPD-associated ED visits were collected from Taiwan Environmental Protection Administration air monitoring stations, Central Weather Bureau stations, and the Taiwan National Health Insurance database in Taipei area. We used a case-crossover study design and conditional logistic regression models with odds ratios (ORs), and 95% confidence intervals (CIs) for evaluating the associations between the environmental factors and COPD-associated ED visits. Analyses showed that PM_2.5, O₃, and SO₂ had significantly greater lag effects (the lag was 4 days for PM_2.5, and 5 days for O₃ and SO₂) on COPD-associated ED visits of the elderly population (65-79 years old). In warmer days, a significantly greater effect on elderly COPD-associated ED visits was estimated for PM_2.5 with coexistence of O₃. Additionally, either O₃ or SO₂ combined with other air pollutants increased the risk of elderly COPD-associated ED visits in the days of high relative humidity and air pressure difference, respectively. This study showed that joint effect of urban air pollution and meteorological factors contributed to the COPD-associated ED visits of the susceptible elderly population in the largest metropolitan area in Taiwan. Government authorities should review existing air pollution policies, and strengthen health education propaganda to ensure the health of the susceptible elderly population.

Clinical Characteristics of Exacerbation-Prone Adult Asthmatics Identified by Cluster Analysis

PURPOSE

Asthma is a heterogeneous disease characterized by various types of airway inflammation and obstruction. Therefore, it is classified into several subphenotypes, such as early-onset atopic, obese non-eosinophilic, benign, and eosinophilic asthma, using cluster analysis. A number of asthmatics frequently experience exacerbation over a long-term follow-up period, but the exacerbation-prone subphenotype has rarely been evaluated by cluster analysis. This prompted us to identify clusters reflecting asthma exacerbation.

METHODS

A uniform cluster analysis method was applied to 259 adult asthmatics who were regularly followed-up for over 1 year using 12 variables, selected on the basis of their contribution to asthma phenotypes. After clustering, clinical profiles and exacerbation rates during follow-up were compared among the clusters.

RESULTS

Four subphenotypes were identified: cluster 1 was comprised of patients with early-onset atopic asthma with preserved lung function, cluster 2 late-onset non-atopic asthma with impaired lung function, cluster 3 early-onset atopic asthma with severely impaired lung function, and cluster 4 late-onset non-atopic asthma with well-preserved lung function. The patients in clusters 2 and 3 were identified as exacerbation-prone asthmatics, showing a higher risk of asthma exacerbation.

CONCLUSIONS

Two different phenotypes of exacerbation-prone asthma were identified among Korean asthmatics using cluster analysis; both were characterized by impaired lung function, but the age at asthma onset and atopic status were different between the two.

Emergency Department Visits for Asthma Exacerbation due to Weather Conditions and Air Pollution in Chuncheon, Korea: A Case-Crossover Analysis

Purpose

This retrospective study was conducted to estimate the effects of climate factors and air pollution on asthma exacerbations using a case-crossover analysis.

Methods

Patients who visited the emergency department (ED) of 2 university hospitals in Chuncheon for asthma exacerbations from January 1, 2006, to December 31, 2011, were enrolled. Daily average data for meteorological factors (temperature, daily temperature range, relative humidity, wind speed, atmospheric pressure, presence of rain, solar irradiation, and presence of fog) and the daily average levels of gaseous air pollutants (SO₂, NO₂, O₃, CO, and PM₁₀) were obtained. A case-crossover analysis was performed using variables about the weather and air pollution at 1-week intervals between cases and controls before and after ED visits.

Results

There were 660 ED visits by 583 patients with asthma exacerbations. Low relative humidity (lag 1 and 2) and high wind speed (lag 1, 2, and 3) were associated with ED visits for asthma. Fog (lag 2) showed protective effects against asthma exacerbations in Chuncheon (risk increase: -29.4% [95% CI=-46.3% to -7.2%], P=0.013). These relationships were stronger in patients ≤19 years old than in those >60 years old. High levels of ambient CO (lag 1, 2, and 3) and NO₂ (lag 2 and 3) were associated with decreased ED visits for asthma. However, there were no significant relationships among levels of ambient CO or NO₂ and asthma exacerbations after adjusting for wind speed and relative humidity.

Conclusions

High wind speed and low humidity were associated with an increased risk of asthma ED visits. Fog was associated with a decreased risk of asthma ED visits after controlling for seasonal variations in weather and air pollution.

Association between children's forced vital capacity and long-term exposure to local ambient temperature in China: A national cross-sectional survey

It is well documented that short-term exposure to extreme ambient temperature is associated with respiratory disorder. However, few studies have assessed the long-term effect of temperature on children's lung function. The present study aimed to investigate the association between long-term exposure to local ambient temperature and children's forced vital capacity (FVC) in China. We analyzed the FVC data of 71,768 children from the 2010 Chinese National Survey on Students' Construction and Health (CHNSCH), and local annual average ambient temperature, relative humidity, air pollutants data from China Meteorological Administration and Ministry of Environment Protection of China. Generalized additive model (GAM) with non-linear function was used to examine the effect of ambient temperature on children's FVC. The results showed that low temperature was significantly associated with decrease of FVC in Chinese children within certain temperature range while adjusting for individual characteristics, socioeconomic conditions, air pollutants and relative humidity. The largest alteration of FVC related to the annual average temperature difference among cities from 20.4°C to 4.5°C was observed, being 242.7ml (95%CI: 220.0, 265.3) decrease in FVC. The similar association was found in both physically active and inactive children, while the largest alteration of FVC related to the temperature difference reached 329.1ml (95%CI: 296.7, 361.6) in physically active children and 290.5ml (95%CI: 255.7, 325.3) in physically inactive ones. Public health policy should be developed for protecting children's respiratory health during growth and development in some areas with cold weather. Key message What is the key question? Few studies have assessed the long-term effect of temperature on children's forced vital capacity (FVC). We analyzed the Chinese national survey data to clarify the association between children's forced vital capacity and long-term exposure to local ambient temperature. What is the bottom line? Our study found that low temperature was significantly associated with decrease of forced vital capacity in children of 30 cities in China. The largest alteration of FVC related to the temperature difference from 20.4°C to 4.5°C was observed, being 242.7ml (95%CI: 220.0, 265.3) decrease in FVC. Why read on? The presented study provide some evidence about long-term effect of temperature on children's respiratory health and public health policy should be developed for protecting children from adverse effects of low temperature on their respiratory health during growth and development in some areas with cold weather.

Outdoor temperature changes and emergency department visits for asthma in Seoul, Korea: A time-series study

BACKGROUND

Extreme temperatures and temperature changes are known indicators of climate change, and large temperature variations for several consecutive days may affect human health such as exacerbating respiratory symptoms. The objective of this study was to determine the association between outdoor temperature change and asthma-related emergency department visits. In particular, this study examined seasonality and identified susceptible populations, such as the elderly.

METHODS

The health data for asthma-related emergency department visits were collected from July 1, 2007, to December 31, 2010 in Seoul, Korea, through the National Emergency Department Information System of the National Emergency Medical Center and we defined temperature change as the absolute difference of mean temperature between the current day and the previous day. We applied generalized linear models with an allowance of over-dispersion for quantifying the estimated effects of temperature change on asthma-related emergency department visits, adjusting for meteorological conditions, air pollution, and time trend.

RESULTS

In general, temperature change was adversely associated with asthma-related emergency department visits, with a 1-unit increase of temperature change associated with a 3.5% (95% CI 0.7, 6.4%) increase in emergency department visits. In addition, seasonal variation after adjusting for mean temperature and diurnal temperature range had an adverse effect in spring, summer, and fall and a protective effect in winter. Patients aged ≥65 years experienced the most prominent effect during the fall, with a 17.9% (95% CI 4.1, 33.6%) increase in emergency department visits per 1-unit increase of temperature change, whereas the other seasons showed no statistically significant association.

CONCLUSIONS

Along with diurnal temperature range, temperature change may be an alternative indicator of climate change. Temperature change variables are well-known and easy to communicate with the public relative to the health effects of outdoor temperature fluctuations.

Cold spells and the risk of hospitalization for asthma: New York, USA 1991-2006

PURPOSE

A study was conducted to investigate whether prolonged periods of very cold temperatures were associated with an increased risk of hospitalization for asthma.

METHODS

Hospitalization admissions with a principal diagnosis of asthma were identified in New York State, USA, for the months November through April from 1991 to 2006. A cold spell was defined as three or more consecutive days where the daily mean of universal apparent temperature (UAT) within a week prior to admission was at the 10th percentile or less. The percentage change in asthma hospitalizations during and after a cold spell was compared to the average daily number of hospitalizations preceding the cold spell using time series analysis.

RESULTS

The average temperature during winter cold spells (December through March) was -15 °C, compared to -6 and -2 °C for cold spells in November and April, respectively. Cold spells during the winter months were associated with a mean decline of 4.9 % in asthma admissions statewide (95 % CI -7.8, -1.9 %). After a cold spell, no statistically significant changes were apparent during the winter months, but asthma hospitalizations increased after cold spells in the transitional months of November (mean = 9.6, 95 % CI 5.5, 13.9 %) and April (mean = 5.0, 95 % CI 1.2, 9.0 %).

CONCLUSIONS

The results suggest that during prolonged periods of severe cold asthmatics may adhere to medical guidelines and limit their exposure, thereby preventing exacerbations. They may be less likely to alter their behavior in the more moderate months of November and April.