Association between traffic-related air pollution and hospital readmissions for rheumatoid arthritis in Hefei, China: A time-series study☆
Graphical abstract
Introduction
Rheumatoid arthritis (RA) is a chronic systemic inflammatory disease characterized by abnormal synovial hyperplasia and progressive destruction of cartilage and bone, affecting approximately 1%–2% of the adult population worldwide (Doran et al., 2002; McInnes and Schett, 2011). The etiology of RA may involve interactions between genetic and environmental risk factors. A variety of extra-articular RA manifestations, such as vasculitis, pericarditis and lung involvement, not only complicate treatment and exacerbate patient outcomes, but may also lead to excess mortality (Turesson and Matteson, 2004; Turesson et al., 2002). Of note, almost all the anatomic structures of the lung or upper airway tracts are potential targets of autoimmune mediated injury in RA patients (Fischer and du Bois, 2012).
In the last few years, a growing number of studies have found that exposure to cigarette smoke, silica dust and mineral oil through the respiratory tract are possible risk factors for RA pathogenesis (Criswell et al., 2002; Stolt et al., 2005; Sverdrup et al., 2005). Ambient air pollution consists of a heterogeneous mixture of anthropogenic and geogenic air pollutants containing free radicals or substances that are capable of driving free radical reactions (Kelly, 2003). In particular, road transport seriously affects urban air quality through vehicle emissions, causing a wide range of adverse effects on public health (Jakubiak-Lasocka et al., 2015). The harmful inhalants may be involved in the biologic mechanisms, such as activating the immune system and eliciting inflammatory responses (Donaldson et al., 2001; Tornqvist et al., 2007), indicating the potential role of airborne environmental factors in the development of RA. To date, findings in previous epidemiologic studies on the association between RA and traffic-related air pollution are inconclusive, most of which were limited to industrialized Western countries (Bernatsky et al., 2017; Chang et al., 2016; De Roos et al., 2014; Hart et al., 2009, 2013a, 2013b; Jung et al., 2017; Shin et al., 2019). For example, a large-scale prospective cohort in the Nurses’ Health Study (NHI) found that residents living within 50 miles of major roadways had an approximately 31% increased risk of RA, compared with residents living more than 200 miles away (Hart et al., 2009). In addition, another prospective cohort study in the United States (US) which followed up 111,425 female nurses did not observe any increased risk of RA after exposure to respirable suspended particulates (RSP/PM10), particulate matter ≤2.5 μm in aerodynamic diameter (PM2.5) or nitrogen dioxide (NO2) (Hart et al., 2013b). However, a longitudinal study suggested an increased risk of RA among people exposed to high concentrations of NO2 (Chang et al., 2016).
As a tractable metric of quality of healthcare, hospital readmissions shortly after discharge has been considered as a sign of poor patient prognosis (Ansari et al., 1995). Thus, effectively controlling readmission rate is of great significance for the management of RA patients. The traffic-related air pollutants mainly include PM2.5, PM10, NO2 and carbon monoxide (CO) (Alotaibi et al., 2019; Liang et al., 2018). In the present time-series study, we aimed to investigate the association between traffic-related air pollutants and hospital readmissions for RA in Hefei, and to explore whether it differed by subpopulations and season.
Section snippets
Study area
This study was conducted in Hefei (31°52′ N, 117°17′ E), the capital city of Anhui Province and one of the core cities of Wanjiang City Belt. Hefei covered a total area of 11,445.1 km2 and had a population of 8.087 million by the end of 2018. Hefei features a subtropical humid monsoon climate with moderate rainfall. With the increasing pace of urbanization and industrial expansion in Hefei, the sharp increase in the number of motor vehicles has further exacerbated the air quality of this city.
Readmission data
Descriptive analysis
A total of 1153 hospital readmissions were reported in Hefei from 2014 to 2018. Among them, 952 were females (82.6%) and 494 aged over 65 years old (42.8%), with an average age of 60.2 years. The summary statistics of daily data on meteorological variables, traffic-related air pollutants and hospital readmissions for RA in Hefei during the study period were shown in Table 1. There were more hospital readmissions for RA in warm season than in cold season (611 vs. 542). The mean concentrations of
Discussion
Traffic-related air pollution, acting as a trigger for the development of multiple autoimmune diseases including RA, has been extensively investigated in the last few years (Zhao et al., 2019b). However, these findings were somewhat controversial. For instance, a Canadian nested case-control study did not find any associations between any specific traffic-related air pollutants and RA (De Roos et al., 2014). In contrast, a large-scale retrospective cohort study found positive associations
Conclusion
In summary, this time-series study provided further evidence that exposure to high concentrations of PM2.5 and NO2 were associated with an increased risk of RA hospital readmissions in Hefei, China. Stratified analyses indicated that females and the elderly appeared to be more susceptible to high-concentration PM2.5 and NO2 exposure. The relationship between high-concentration PM2.5 exposure and the risk of RA hospital readmissions remained significant in both warm and cold seasons, while
Funding
This work was supported by the National Natural Science Foundation of China (Grant Number 81872687).
Author statements
Qian Wu and Hai-Feng Pan: Conceptualization. Zhiwei Xu: Methodology, Qian Wu: Software and Data curation, Qian Wu and Zhiwei Xu: Writing- Original draft preparation, Visualization. Yi-Lin Dan and Kun Xiang: Investigation. Jian Cheng: Supervision. Chan-Na Zhao and Yan-Mei Mao: Software, Validation. Yu-Qian Hu and Yi-Sheng He: Writing- Reviewing and Editing.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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This paper has been recommended for acceptance by Dr. Payam Dadvand.
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Qian Wu and Zhiwei Xu contributed equally to this work and should be considered co-first authors.