This approach is similar to methods used in earlier studies to compare mortality risk on heat wave days with non-heat wave days (Anderson and Bell 2009; Hajat et al. 2006); however, our model extends the earlier method by allowing risk of mortality to differ by heat wave.
Background: In recent years, several scoring systems have been developed to describe the severity of illness, to establish the individual prognosis, and to group the intensive care unit (ICU) patients by predicted risk of mortality.
We divided the difference by the risk of mortality in 2003 to obtain the relative contribution of each explanatory variable.
However, the pathways by which risk of mortality is reduced have not been fully extrapolated.
These patients had similar severity of illness scores and a similar degree of respiratory failure (as measured by Pediatric Risk of Mortality scores and PaO2 FiO2 ratios).
Severity was rated by Pediatric Risk of Mortality (PRISM) 3 scores for patients <18 years and the Simplified Acute Physiology Score (SAPS) II for patients ≥18 years, when available.
The annual mortality rate was calculated by multiplying the mortality rate of the target patients (Japanese women aged 50 years) by the risk of mortality based on reports indicating that the mortality risk of patients with ITP and a platelet count <30 × 10/L is 4.2-fold higher than that of healthy subjects, compared to 1.8-fold higher than that of patients with a platelet count ≥30 × 10/L [ 1].
To calculate life expectancy, life tables based on the general U.S. population were used by which the risk of mortality was adjusted by age, sex, race, diabetes, and VI status.
Sensitivity analyses were conducted by comparing the fixed and random effects models as well as by evaluating the risk of mortality in studies with a low risk of bias only.
Data collected on admission included: demographic data, severity of illness as estimated by the Pediatric Risk of Mortality (PRISM) III score [ 27], organ dysfunction as estimated by the Pediatric Logistic Organ Dysfunction PELODD) score [ 28] and the MODS score [ 29].
