| ObjectiveTo set up the model of exposure-response relationship on air pollution and residents' health in the urban area of Lanzhou, it is estimated quantitatively that impact of ambient air pollution on daily respiratory and circulatory hospitalization and the lag effect of this impact is also analysed. The loss of hospital charges are calculated by exposure-response relationship. It is provided the scientific evidence for forecasting, predicting, preventing and controlling diseases of respiratory system and circulatory system.MethodsThe data on Air Pollution Index (API), meteorology and the hospitalization of respiratory system and circulatory system diseases from Jan.1st 2004 to Oct.31st 2007 in the area of Lanzhou City were collected. Generalized additive model (GAM) of Poisson regression was employed for analyzing the effect of ambient air on daily hospitalization of respiratory system and circulatory system diseases, according to gender, age and disease types, on the bases of using non-parametric smooth function to control the long-term trends, cyclical and meteorological factors. And the loss of charges for respiratory and circulatory hospitalization after one time air pollution are calculated by value of the relative risk (RR).Results1. The analysis of relations on API level in the urban area of Lanzhou, weather condition indicators and daily hospitalization.From 2004 to 2007, the mean daily API level is 109.40, and air quality was marked lightly polluted over 35.52% of days of the years according to their API levels, and the major pollutant affecting air quality was PM10. Over 4 years of following API level, weather condition indicators and respiratory and circulatory diseases hospital admissions, we have found significant seasonal fluctuations on those factors. From November to January and March to April, we have more people hospitalized for respiratory and circulatory diseases,and decreases during summer. Coronary heart disease and pneumonia follow the pattern more obvious. This pattern is similar to API and pressure fluctuation, in spring and winter higher movement, summer and autumn lower fluctuation, while the movement of average daily temperature, average daily humidity and wind speed is opposite to the fluctuation pattern.2. Impact of ambient air pollution on daily respiratory hospitalization in Lanzhou.For every one of IQR (48 units) increased in daily API, there was a 5.50 (95%CI: 4.03%,6.99%) increased in respiratory diseases admissions, and this influence has a certain lag effect. The Relative Risk(RR) reached its highest 1.0583 (95%CI 1.0397-1.0772) among males one day after the lag effect, while the RR for females reached its highest when API increased. Except day 3 and day 4 after the lag effect females have lower RR levels than males do. Ambient air pollution was more likely to affect under 15-year-old and over 65-year-old and the RR level reached its highest1.0595 (1.0407-1.0787) and 1.0560 (1.0306-1.0821) at day 3 and day 4 after the lag effect respectively. Right the day when API increased, there were a number of increase in hospitalization of pneumonia and upper respiratory tract infection (URTI), and their RR levels were 1.0595(1.0407-1.0787) and 1.0560 (1.0306-1.0821) respectively. And the lag effect on pneumonia patients was higher than upper respiratory tract infection (URTI). The study shows that air pollution considerably affects the morbidity of respiratory diseases among urban residents, and there are certain level of disparities on those impacts according to different gender, age and respiratory disease type.3. Impact of ambient air pollution on daily circulatory hospitalization in Lanzhou.For every one of IQR(48 units) increased in daily API, there was associated with approximately from 1.35% to 3.62% increase in daily hospital admissions for circulatory system from current day to day 5 after the lag effect. The Relative Risk(RR) reached its highest 1.04226(95%CI 1.02510-1.05881) among males five day after the lag effect, the RR for females is higher than males only in four day after the lag effect. From current day to day 5 after the lag effect,the RR level is higher than 1.02 for over 65-year-old. And the RR level by day 2 to day 5 after the lag effect for 16 to 64 years old was statistical significance. Ambient air pollution was more likely to affect hypertension patients and blood vessel of brain disease and the RR level reached its highest 1.07291(95%CI 1.04448～1.10211) and 1.04372(95%CI 1.01432～1.07397) at day 5 after the lag effect, the RR reached its highest 1.02521(95%CI 1.00157～1.04941) among coronary disease day 2 after the lag effect.4. Damage assessment of hospital costs over Air pollution in Lanzhou City.2.07 million residents of Lanzhou City was accounted for our study. the average daily numbers of hospitalized patients who have respiratory or circulatory diseases is 34.88 or 73.73. Hospitalization cost according to API increase of 48 units in Lanzhou City is 43,251 yuan or 195,023 yuan, the excess number of male patient, per capita hospital costs were higher than the loss of female. Hospital charges for the elderly is higher than adults and children. In respiratory disease, pneumonia hospitalization costs much higher than URTI. In circulatory system diseases, hospital charges goes from coronary heart disease, hypertension and down to cerebrovascular disease. When the air pollution concentrations is at the threshold air qualityⅡ, air pollution in Lanzhou City costs of more than 50 million yuan over the average annual hospitalization.ConclusionThe study shows that air pollution considerably affects the morbidity of respiratory system and circulatory system diseases among urban residents, and there are certain level of disparities on those impacts according to different gender, age and disease type. Reducing emissions of air pollutants is an effective and economical way to secure and improve health standards of urban citizens. |
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