OBJECTIVES: Cohort studies of associations between air pollution and health have used exposure prediction approaches to estimate individual-level concentrations. A common prediction method used in Korean cohort studies is ordinary kriging. In this study, performance of ordinary kriging models for long-term particulate matter less than or equal to 10 mum in diameter (PM10) concentrations in seven major Korean cities was investigated with a focus on spatial prediction ability. METHODS: We obtained hourly PM10 data for 2010 at 226 urban-ambient monitoring sites in South Korea and computed annual average PM10 concentrations at each site. Given the annual averages, we developed ordinary kriging prediction models for each of the seven major cities and for the entire country by using an exponential covariance reference model and a maximum likelihood estimation method. For model evaluation, cross-validation was performed and mean square error and R-squared (R2) statistics were computed. RESULTS: Mean annual average PM10 concentrations in the seven major cities ranged between 45.5 and 66.0 mug/m3 (standard deviation=2.40 and 9.51 mug/m3, respectively). Cross-validated R2 values in Seoul and Busan were 0.31 and 0.23, respectively, whereas the other five cities had R2 values of zero. The national model produced a higher crossvalidated R2 (0.36) than those for the city-specific models. CONCLUSIONS: In general, the ordinary kriging models performed poorly for the seven major cities and the entire country of South Korea, but the model performance was better in the national model. To improve model performance, future studies should examine different prediction approaches that incorporate PM10 source characteristics.
Air Pollution ; Busan ; Cohort Studies ; Korea ; Particulate Matter* ; Seoul ; Spatial Analysis*

A sudden increase in intracranial pressure due to spontaneous subarachnoid hemorrhage or head trauma may result in intraocular hemorrhage. To determine the prognostic implications, the incidence of this after SAH, and 157 consecutive patients with spontaneous subarachnoid hemorrhage were prospectively studied by means of indirect fundoscopy. In 20(12.7%) of these patients, intraocular hemorrhage was seen on initial examination. Mean initial Hunt and Hess and Fisher CT grades were higher in SAH patients with intraocular hemorrhage than in those without(3.57 and 3.57 ; 2.56 and 2.70, respectively, the differences were those without statistically significant. The anatomic distribution of ruptured aneurysm was different in patients with intraocular hemorrhage and thoes without. The overall mortality rate was 19%(26 of 137 patients), but 50%(10 of 20 patients) with intraocular hemorrhage died. Based on the results of the above study we can conclude that in cases of spontaneous subarachnoid hemorrhage, intraocular hemorrhage is not infrequent and that its prognosis is poor.
Aneurysm, Ruptured ; Craniocerebral Trauma ; Hemorrhage* ; Humans ; Incidence ; Intracranial Pressure ; Mortality ; Prognosis ; Prospective Studies ; Subarachnoid Hemorrhage*