3.1 Trends in the rates of AR outpatient visits between 2008 and 2017
During the 10 years, a total number of 917240 outpatients attended the Department of Otolaryngology-Head and Neck Surgery at the first affiliated hospital of Chongqing Medical University. 20534 of these were diagnosed with AR. Figure 1a showed the monthly number for outpatients, clinical visit for AR and the AR ratio. It demonstrated that there were seasonal variations in AR ratio from 2008 to 2017. The monthly number for outpatients and clinical visit for AR gradually increased every year. The AR ratios showed one peak during every year and it was in August and September; 7,10,11 showed sub-maximum AR ratios; Meanwhile, 2,3 showed the lowest ratios of AR visits. In Figure 1b, we saw that the AR ratios increased after an apparent period of stability during 2008-2012. In Figure 1c, the regression analysis showed that the AR ratio were in cubic function curve relation with time(R=0.650, F=28.313, p<0.01). According to age, patients in 20-39 y showed stronger increase in the rates of AR outpatient visits(Figure 1d).
3.2 Trends in the aeroallergen of AR outpatient visits between 2008 and 2017
As shown in Figure 2, in the AR patients, the dermatophagoides farine and dermatophagoides pteronyssinus yielded the highest number of positive responses(mean=95.653% and 95.668%) followed by humulus pollen(mean=67.852%) and artemisia pollen(mean=58.603%). Meanwhile, yeasts and tobacco yielded the least(36.581%, 33.223%). It demonstrated that dermatophagoides farine and dermatophagoides pteronyssinus were the most common allergens in Chongqing area. Moreover, the positive rates of artemisia pollen and humulus pollen showed an obviously decreasing tendency from June 2014 and then the positive rate of cockroach showed the third highest from February 2015.
3.2 Trends of mono-sensitization to mite and poly-sensitization in AR during 10 years
As shown in Figure 3a, firstly, this study showed that polysensitization was always very common as about 4/5-2/3 of patients were sensitized to poly allergens. Secondly, we found that the rate of mono-specific sensitization to dust mite allergen(including dermatophagoides farine and dermatophagoides pteronyssinus) was on the increase again after an apparent period of stability from 2008-2013. In 2008, 9.755% of the overall AR patients had a positive prick test for only dust mite allergen(including dermatophagoides farine and dermatophagoides pteronyssinus), while 36.353% of them were sensitized to dust mite allergen in the 2017. In 2008, the poly sensitized subjects in AR patients were 90.245%, while they were 63.647% in the 2017. In Figure 3b, the regression analysis showed that the rate of mono-sensitization to mite presented increase as cubic function curve(R=0.789, F=63.701, p<0.01). According to age, the results demonstrated that patients in 20-39 y showed stronger increase in the rate of mono-sensitization(Figure 3c).
3.4 Characteristics of air pollutants
Figure 4a demonstrated the data for the monthly air pollution variables(SO2, NO2, CO, O3, PM2.5, PM10) in Chongqing during 2013-2017. The results showed that, monthly average concentrations of PM10 varied from 51 ug/m3 to 191 ug/m3; PM2.5 varied from 27 ug/m3 to 138 ug/m3; SO2 varied from 7 ug/m3 to 45 ug/m3; NO2 varied from 14 ug/m3 to 57 ug/m3; O3 varied from 19 ug/m3 to 153 ug/m3; CO varied from 523 ug/m3 to 1770 ug/m3. The concentrations of SO2 and PM2.5 showed slow decrease from January 2013 to December 2017. During winter(heating period), the concentration of SO2 was higher.
Pearson correlation coefficients of air pollutants were shown in Table 1. SO2, NO2, PM10, PM2.5 and CO had significant positive correlations with each other(p < 0.05), whereas O3 had a significant negative correlation with the other five air pollutants. This correlation was consistent with previous reports(21,22) and attributed to the stationary fossil fuel combustion-related pollutants(SO2 and PM) and the traffic-related pollutant NO2 (23). PM10 and PM2.5 were highly correlated (correlation coefficient r = 0.938). PM10 were moderately correlated with SO2(r=0.591) and weakly correlated with CO(r=0.381); PM2.5 were strongly correlated with SO2(r=0.738) and moderately correlated with CO(r=0.424); NO2 were moderately correlated with CO(r=0.482).
3.5 Exposure-Response associations between air pollutants and AR outpatient visit
In this study, we used non-parametric generalized additive model (GAM) to analyze the exposure-response relationships for air pollutants with outpatient visits for
AR during Chongqing city in 2008-2017. Firstly, we evaluated the association between air pollutants and the AR outpatient visit(Table 2a). No significant correlations were found between the AR visits and the concentrations of SO2, NO2, CO, O3, PM2.5, PM10. Moreover, we explored the relationships for air pollutants with outpatient visits for mono-mite-sensitized AR.
According to the statistical results, the mono-mite-sensitized AR visits were significantly correlated with the concentration of atmospheric SO2, PM10 and PM2.5. However, there was no obvious correlation between the mono-mite-sensitized AR visits and other air pollutants, including NO2、CO、O3. In the multiple influencing factors GAM models, the contribution of the SO2, PM10 and PM2.5 to the mono-mite-sensitized AR visits was 67.4% with significant impacts on the change of mono-mite-sensitized AR visits. Based on the analysis of the effect of multi-factors on the change of mono-mite-sensitized AR visits, there were linear relationships between mono-mite-sensitized AR visits and PM2.5, PM10 concentrations, and non-linear relationship between mono-mite-sensitized AR visits and SO2 concentration(Table 2b). Figure 4b showed the exposure-response relationships for the concentration of SO2, PM10 and PM2.5 with outpatient visits for AR.