Table 2.
Rate ratios and 95% confidence intervals for the multilevel Poisson regression model
| Variable | Rate Ratio | 95% Confidence Interval | P Value |
|---|---|---|---|
| Fixed intercept | |||
| −5.69 (−5.74, −5.64) | |||
| Fixed effects (rate ratios) | |||
| Age | 0.999 | (0.976, 1.023) | P = .9506 |
| Systolic blood pressure | 0.912 | (0.891, 0.933) | P < .0001 |
| Respiratory rate | 1.036 | (1.013, 1.059) | P = .0021 |
| Low sodium serum concentration (< 136 mEq/L) | 1.098 | (1.04, 1.159) | P = .0008 |
| Low serum hemoglobin (< 10.0 g/dL) | 1.151 | (1.079, 1.227) | P < .0001 |
| Serum urea nitrogen | 1.167 | (1.141, 1.194) | P < .0001 |
| Cancer | 1.239 | (1.16, 1.324) | P < .0001 |
| Chronic obstructive pulmonary disease (COPD) | 1.109 | (1.056, 1.165) | P < .0001 |
| Cerebrovascular disease | 1.021 | (0.963, 1.082) | P = .4923 |
| Hepatic cirrhosis | 1.065 | (0.827, 1.37) | P = .6262 |
| Dementia | 1.005 | (0.924, 1.093) | P = .9047 |
| Variance of random effect | 0.0222 | ||
The rate ratios for the 4 continuous variables denote the relative change in the rate of the outcome associated with a one‐standard deviation change in the covariate. Age was standardized by centering at the mean age (76.4 years) and dividing by the standard deviation (11.6). For systolic blood pressure, the corresponding numbers were 147.0 and 29.2, respectively. For respiratory rate, the corresponding numbers were 24.9 and 6.1, respectively. For serum urea nitrogen, the corresponding numbers were 9.4 and 4.6, respectively. The sample consists of 7162 patients treated at 96 hospitals.