Association between children's forced vital capacity and long-term exposure to local ambient temperature in China: A national cross-sectional survey
Graphical abstract
The largest alteration of forced vital capacity (FVC) related to the temperature difference was observed from 20.4 °C to 4.5 °C, with 242.7 ml (95%CI: 220.0, 265.3) decrease in FVC.
Introduction
Lung function is a noninvasive measurement of respiratory health and has been widely used in previous studies to explore the effects of environmental factors on respiratory health (Li et al., 2012). There were numerous previous studies focus on the relationship between temperature and adverse cardiovascular events (Guo et al., 2013a, Guo et al., 2013b, Michelozzi and De Sario, 2010, Peng et al., 2008), while only a few studies have examined the effects of temperature on lung function (Koskela et al., 1994, Li et al., 2014, Mann et al., 1993, Wu et al., 2014). However, most of the above studies focused on estimating the effects of temperature on adults.
In comparison to adults, children are impacted by temperature change more seriously (Sheffield and Landrigan, 2011). Children's susceptibility could be resulted from many factors such as the lung defense mechanisms against the changes of climatic circumstance which are not fully evolved compared with adults, the continuing process of lung growth and development, immature host defenses, high rates of infection with respiratory pathogens, less effective heart adaptation capacity, higher exposure per unit body weight and more outdoor activity which increase exposure to ambient environment (Committee on Sports Medicine and Fitness and American Academy, 2000, Bennett et al., 2008, Brunekreef and Holgate, 2002, Kim, 2004, Phalen et al., 1985). A better understanding of the impacts of ambient temperature on children's lung function will provide important information for developing public health policy.
However, we only found one study conducted in a city of China had used the temperature of a few weeks before as exposure to analyze the short-term effect of temperature on lung function of children aged from 8 to 12 years (Li et al., 2014). Unlike the short-term effects, which could be caused by the immediate response of bronchus or airways, the temperature on the long-term, relating to the local average climate, latitude and geographical location of the cities, could affect children's lung function through some indirect mechanism (e.g., immunological mechanism). But we only find one study conducted in London analyzed the long-term effect of temperature on lung function on unhealthy persons (Donaldson et al., 1999). As we know, no previous study has investigated the long-term effect of ambient temperature on children's lung function. Identifying whether there are the long-term effect of ambient temperature on children's lung function will replenish our understanding of the adverse impacts of ambient temperature.
In this paper, we used the data of annual average ambient temperature in 30 cities of China, and individual data of 71,768 children from the Chinese National Survey on Students' Construction and Health (CHNSCH) in 2010, the largest Chinese national cross-sectional survey, to discuss the long-term effect of local climate on children's forced vital capacity (FVC), a common indicator for lung function. The study specifically aimed to identify whether there are the long-term effect of ambient temperature on children's FVC after adjusting for air pollutants, relative humidity and individual characteristics.
Section snippets
Study population
We collected the data of children from the 2010 CNSSCH, which was conducted every five years since 1985, jointly launched by the Ministry of Education, the Ministry of Health, the Ministry of Science and Technology, the State of Nation Affairs, and the State Sports General Administration of People's Republic of China (Song et al., 2014). It is the largest nationally representative sample of school-age children in China. The participants were primary and middle school students aged 7–18 years of
Results
There were 71,768 children in this study, with the total sample of each city from 2348 to 2400, including about 100 subjects in each sex-age subgroup. The proportion of female was from 49% to 50% and the mean age was from 12.4 to 12.5 years in each city (Table 1). Fig. 1 shows geographic location of the 30 cities in this study, being very disperse and representative of different parts of China. There was an obvious geography variation in the annual average temperature among different cities in
Discussion
To our knowledge, it is the first study to examine the long-term effect of ambient temperature on children's lung function (FVC) in China. By examining the largest representative sample of school-age children in China (N = 71,768), we found that decrease in annual average ambient temperature was associated with decrease in FVC of children within certain temperature difference and the largest changes of FVC could reach 242.7 ml (95%CI: 220.0, 265.3).
The results of our study were consistent with
Conclusion
In conclusion, our study found that low ambient temperature was significantly associated with decrease of forced vital capacity in Chinese school children. Public health policy such as improvement of the indoor climate of dwellings (WHO, 1997) 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.
Funding
Data collection was jointly supported by the Ministry of Education, General Administration of Sport, the Ministry of Health, State Ethnic Affairs Commission, Ministry of Science and Technology, Ministry of Finance, People's Republic of China. Data analyses of the present study were supported by a grant from China Medical Board (11-064). YG is supported by the University of Queensland Research Fellowship and the Career Development Fellowship of Australian National Health and Medical Research
Competing interests
The authors have declared that no competing interest exists.
Ethics approval
The study project was approved by the Medical Research Ethics Committee of the University of Queensland (#2011001199).
Acknowledgement
We thank WK Liao, WH Xing, and X Zhang for their permission on accessing the data of 2010 Chinese National Survey on Students' Constitution and Health. We also appreciate the students who participated in the survey for their cooperation.
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