Effects Of Air Pollutions On The Morbidity And Mortality Of T2DM In A Retrospective Cohort Study

Objective:A growing number of epidemiological evidences show that ambient air pollution may also promote the occurrence and development of type 2 diabetes（T2DM）.A host of the relevant studies were from European and American countries,where the level of air pollution is lower.While many cities in China were more polluted and there are fewer cohort studies on the association between air pollutants and diabetes.Therefore,this study was based on a 12-year retrospective cohort of four cities in northern China,and explores the association between long-term exposure to high concentrations of air pollutants and T2DM morbidity and mortality outcomes.Based on this,further analyzed of sociodemographic characteristics and other factors modification of health effects,screening of susceptible populations,which provided a basis for assessment of health effects of air pollution and prevention and control of diabetes.Methods:1.Using a retrospective cohort study method,this study was conducted from 1998to 2009 on residents who met the inclusion criteria in four cities in northern China（Rizhao,Tianjin,Shenyang,and Taiyuan）.Questionnaires were used to acquire demographics,lifestyle,and disease history.The study subjects self-reported the prevalence of T2DM and the date of diagnosis.Informations on death outcomes were provided by family members and checking at the local centers for disease control and prevention.2.Collecting the daily average concentrations of air pollutants from 15 monitoring stations during 1998-2008,then we use the daily average concentrations to calculate the annual average concentrations.Based on the data from the nearest monitoring station,the level of exposure during an individual’s lifetime was estimated.3.Cox regression model was used to analyze the correlation between atmospheric pollutants and the incidence and death of diabetes in single and multiple pollutant models gradually adjusting related confounding factors,and analyze factors such as age,gender,BMI and atmospheric pollutants exposed interactions.Finally,some sensitivity analyses were carried out.Results:1.A total of 39054 participants were included in the death cohort.During the follow-up,1435 deaths occurred,of which 59 subjects died of T2DM.A total of 525patients with diabetes at baseline were excluded,and 38529 respondents were included in the onset of cohort.1213 new cases of T2DM were reported during the study period,whose crude mortality and cumulative morbidity were 0.15%and 3.15%,respectively.2.During the study period,the average concentrations of three air pollutants(PM₁₀,SO₂,and NO₂)were 143.36±53.52μg/m³,66.71±39.06μg/m³,and 40.74±17.07μg/m³,respectively;The concentration ranges of air pollutions were 58.00-259.40μg/m³,11.00-165.90μg/m³and 16.80-89.47μg/m³,respectively.Spearman correlation analysis was used to observe the correlation between the three air pollutants,and PM₁₀ was correlated with SO₂（r=0.731）.3.Long-term exposure to high concentrations of air pollutants was closely related to the incidence and death of T2DM.For each 10μg/m³ increase in PM₁₀,SO₂,and NO₂,the HR（95%CI）value of incidence of T2DM were 1.799（1.747-1.853）,1.277（1.247-1.308）,and 1.433（1.381-1.488）;the HR（95%CI）values of death of T2DM were 2.272（1.741-2.965）,1.136（1.050-1.229）,and 1.488（1.248-1.774）,respectively.Among them,PM₁₀ has the greatest impact on T2DM,followed by NO₂,and finally SO₂.The results were stable in the two-pollutant model.4.After adjusting for confounding factors,it was observed that the age group<45years and people with lower frequency intake of vegetables were susceptible to T2DM incidence caused by air pollutions;the BMI group<24kg/m²was vulnerable to the incidence of T2DM caused by PM₁₀;inactive exercise group and lower frequency intake of fruits were more susceptible to the onset of T2DM caused by NO₂.5.Multivariate Cox regression results show that age,BMI,smoking,and women were risk factors for T2DM incidence,vegetables and fruits were protective factors for T2DM incidence;age was a risk factor for T2DM death,and women,exercise,and fruits were protection factors for T2DM death.6.Regarding the sensitivity analysis of T2DM incidence,the results of the three pollutants did not change significantly and still have statistical significance.For the T2DM death analysis,after removing the Rizhao monitoring station,it was observed in the sensitivity analysis that SO₂was no related to the death of T2DM.The correlation between them changed.The HR（95%CI）value was 1.073（0.971-1.186）,which was not statistically significant,but the results were still stable in PM₁₀ and NO₂.Conclusions:1.After adjusting for confounding factors,this study suggests that long-term exposure to three air pollutants(PM₁₀,SO₂,and NO₂)may increase the risk of T2DM,with HR（95%CI）values of 1.799（1.747-1.853）and 1.277（1.247-1.308）and 1.433（1.381-1.488）,respectively.2.Long-term exposure to three air pollutants(PM₁₀,SO₂,and NO₂)may increase the mortality the T2DM,with HR（95%CI）values of 2.272（1.741-2.965）,1.136（1.050-1.229）,and 1.488（1.248-1.774）,respectively.3.Research shows that the age group<45 years may be susceptible to T2DM caused by air pollution;the BMI group<24kg/m²may be vulnerable to T2DM caused by PM₁₀;and compared with active exercise group,inactive exercise group may be more susceptible to NO₂ caused by T2DM.Increasing the intake frequency of vegetables and fruits may reduce the risk of T2DM caused by air pollutants.