The Relationship Between Short-term Changes Of Air Pollution And Temperature And Outpatient Visits Of Anxiety And Depression In Xi’an: A Hospital-based Study

BackgroundAs the two most common mental diseases,anxiety and depression have the characteristics of high morbidity rates,seriously threaten the physical and mental health of patients,and increase the social health burden.At present,no effective prevention and treatment methods have been found.In addition,with the rapid development of the economy,climate change has intensified,and the health threats caused by air pollutants and climate change have gradually been paid attention to.At present,the research on anxiety and depression is increasing,but the research on the correlation between short-term air pollution and meteorological factors exposure and anxiety and depression is still relatively limited.Objectives1.To evaluate the association between short-term exposure to air pollutants and the number of outpatient visits for anxiety and depression in Xi’an,and to identify the population susceptible to air pollutants.In addition,further explore the possible differences in the effects of atmospheric pollutants on anxiety and depression between different seasons.2.The distribution lag non-linear model（DLNM）was used to evaluate the correlation between short-term changes in temperature（average temperature,apparent temperature,humidex）and outpatient visits for anxiety and depression in Xi’an,and compare the evaluation effects of these three temperature indicators.Methods1.Collected data on daily anxiety and depression outpatient visits,air pollutant concentrations,and meteorological factors in Xi’an from 2015 to 2019,and conducted descriptive analysis.Spearman’s correlation analysis was used to study the relationship between anxiety and depression visits and meteorological factors and air pollutants.2.The generalized additive model（GAM）was used to evaluate the changes in daily outpatient visits for anxiety and depression and their 95%confidence intervals（CI）corresponding to changes in the concentration of air pollutants per unit（10μg/m³ or 1mg/m³）,and then performed a stratified analysis to identify possible sensitive populations and seasonal differences.3.The DLNM was used to construct the cross-basis functions of the three temperature indicators（average temperature,apparent temperature,and humidex）,respectively,to obtain the exposure-response relationship between the three temperature indicators and anxiety and depression.The Akaike information criterion（AIC）and generalized cross validation（GCV）of the model compared the superiority of these three temperature indicators in measuring the effects of temperature exposure on anxiety and depression outpatient visits.Results1.A total of 67,981 outpatients with anxiety and 88,414 outpatients with depression from2015 to 2019 were included in this study.In the gender composition of outpatients,the total number of female anxiety outpatients was 42,554,and the total number of male anxiety outpatients was 25,427,accounting for 62.60%and 37.40%of the total number of anxiety outpatient visits,respectively.The total number of female depression outpatients was 56,113,and the total number of male depression outpatients was 32,301,accounting for 63.47%and36.53%of the total depression outpatients,respectively.In the age composition of outpatients,there were 19,497 young（≤35 years old）anxious patients,31,526 middle-aged（36-59 years old）anxious patients,and 16,958 elderly（≥60）anxious patients,accounting for 28.68%,46.37%and 24.95%of the total number of anxiety outpatient visits,respectively.The number of young（≤35 years old）depressed outpatients was 29,163,the number of middle-aged（36-59 years old）depressed outpatients was 38,285,and the number of elderly（≥60 years old）depressed outpatients was 20,966,accounting for 32.98%,44.30%and 23.71%of the total number of outpatient visits for depression,respectively.In the seasonal distribution,the total number of patients with anxiety and depression in the cold season/warm season were 33996cases/33985 cases and 44608 cases/43806 cases,respectively.2.Meteorological factors and atmospheric pollutants showed obvious seasonal trends.Air pollutants(PM₁₀,PM_2.5,SO₂,NO₂,CO)showed a seasonal variation pattern of high pollutant concentrations in summer and low pollutant concentrations in winter.O₃ was the opposite,showing a low concentration in summer and a high concentration in winter.Meteorological factors also have obvious seasonal fluctuations.The temperature,relative humidity,precipitation,and sunshine all show a trend of high concentrations in summer and low concentrations in winter.On the contrary,air pressure was low in summer and high in winter.3.Short-term exposure to NO₂ was significantly positively correlated with daily outpatient visits for anxiety and depression,with a lag.Short-term exposure to NO₂ in lag0-lag5 and lag01-lag07 had a significant positive correlation with daily outpatient visits for anxiety.Among them,the correlation between short-term exposure to NO₂ and daily outpatient visits for anxiety was the strongest in lag07,and for every 10μg/m³ increase in NO₂,the corresponding percentage change in outpatient visits for anxiety was 5.45%（95%CI:3.27%,7.63%）.Short-term exposure to O₃ was negatively correlated with anxiety outpatient visits at lag05 and lag07,with the most significant effect at lag07.For every 10μg/m³increase in O₃,the corresponding percentage change in anxiety outpatient visits was-1.56%（95%CI:-2.95%,-0.17%）.Short-term exposure to NO₂ and daily outpatient visits for depression were significantly positively correlated in both the single-day lag model（lag0-lag3,lag5,lag6）and the moving average lag model（lag01-lag07）,with the strongest positive correlation at lag07（5.52%（95%CI:3.92%,7.13%））.Short-term exposure to O₃ was significantly negatively correlated with daily outpatient visits for depression at lag3 and lag03-lag07,with the strongest negative correlation at lag07（-2.12%（95%CI:-3.37%,-0.87%））.The results of the subgroup analysis showed that no significant gender and age differences were observed in the association of air pollutants with anxiety and depression daily outpatient visits.In different visiting seasons,the correlations between short-term exposure to NO₂ and O₃ and daily outpatient visits for anxiety and depression were significantly different between cold season and warm season,and the harmful effect of NO₂and the protective effect of O₃ were stronger in cold season,showing that the harmful effect of NO2 and the protective effect of O3 were stronger in the cold season.The dual-pollutant model showed that after adjusting for other air pollutants,the association between O₃ and outpatient visits for anxiety and depression lost statistical significance,while the association between NO₂ and outpatient visits for anxiety and depression remained significant.4.The average temperature,apparent temperature,and humidex all showed a seasonal variation pattern of high concentrations in summer and low concentrations in winter.The apparent temperature and the humidex were higher than the average temperature peak value,and the apparent temperature was lower than the average temperature and humidex value.5.Low average temperature（-3.0°C,2.1°C）increased the risk of outpatient visits for anxiety and depression,while high average temperature（28.5°C and 32.6°C）has no statistically significant effect on outpatient visits for anxiety and depression.Extreme low temperature of-3.0°C significantly increased the risk of outpatient visits for anxiety on days lag9-lag13,with the strongest risk effect on day lag11,with a corresponding RR of 1.029%（95%CI:1.009%-1.050%）.Moderate low average temperature of 2.1℃reached the strongest risk effect at lag14 days,corresponding to a percentage change of 1.023%（95%CI:1.001,1.045）in the number of outpatient visits for anxiety.Extreme low temperature of-3.0°C significantly increased the risk of outpatient visits for depression at lag10-lag12,with the strongest risk effect at lag11,corresponding to a percentage change of 1.023（95%CI:1.005,1.042）in the number of outpatient visits for depression.6.Low apparent temperature（-7.8℃,-2.0℃）significantly increased the risk of outpatient visits for anxiety and depression,while high apparent temperature（29.9℃,35.6℃）will not have a significant impact on outpatient visits for anxiety and depression.Extremely low apparent temperature of-7.8°C was significantly associated with an increased risk of anxiety outpatient visits at lag10-lag13,with the highest relative risk at lag12,corresponding to a percentage change of 1.030（95%CI:1.006,1.054）in the number of anxiety outpatient visits.A moderately low apparent temperature of-2.0℃in lag13-lag16 increases the risk of outpatient visits for anxiety,and the relative risk is highest at lag14,corresponding to a percentage change of 1.026（95%CI:1.003,1.050）in the number of outpatient visits for anxiety.The extremely low apparent temperature of-7.8℃in lag10-lag12 increases the risk of outpatient visits for depression,and the relative risk is highest at lag12,corresponding to a percentage change of 1.023（95%CI:1.002,1.045）in the number of outpatient visits for depression.7.Low humidex（-3.0,2.1）significantly increased the risk of outpatient visits for anxiety and depression,while high humidex（35.0,42.0）did not significantly affect outpatient visits for anxiety and depression.Extremely low humidex-3.0 increased the risk of anxiety outpatient visits at lag9-lag13,among which the relative risk was highest at lag12,and the percentage change in the number of anxiety outpatient visits was 1.032（95%CI:1.009,1.055）.A moderately low humidex of 2.1 in lag11-lag15 increases the risk of outpatient visits for anxiety,and the relative risk is highest at lag14,corresponding to a percentage change of1.025（95%CI:1.003,1.047）in the number of outpatient visits for anxiety.Extreme low humidex-3.0 increased the risk of outpatient visits for depression in lag3 and lag10-lag13,and the relative risk was highest at lag12,corresponding to a percentage change of 1.025（95%CI:1.005,1.046）in the number of outpatient visits for depression.8.Among the three indicators of temperature and the number of anxiety outpatient visits,the model fit of apparent temperature was the best.Among the three indicators of temperature and the number of outpatient visits for depression,the model fit of average temperature was the best.Conclusions1.Short-term exposure to NO₂ and O₃ had significant positive and negative correlations with daily outpatient visits for anxiety and depression,respectively,and the effects had a hysteresis.In addition,the associations between short-term exposure to NO₂ and O₃ and daily outpatient visits for anxiety and depression were not significantly different between gender and age groups.Seasonal stratified results analysis showed that the associations of the two pollutants with anxiety and depression were more obvious in the cold season.However,there was no significant correlation between short-term exposure to other air pollutants(PM_2.5,PM₁₀,SO₂,CO)and daily outpatient visits for anxiety and depression.2.Low average temperature,low apparent temperature and low humidex were all related to the increase of outpatient visits for anxiety and depression.High mean temperature,high apparent temperature and high humidex were not significantly associated with outpatient visits for anxiety and depression.3.Among the three temperature indicators evaluating the correlation between temperature and anxiety outpatient visits,apparent temperature is slightly better than the other two indicators.Among the three temperature indicators that evaluate the correlation between temperature and the number of outpatient visits for depression,the average temperature is slightly better than the other two indicators.