Volume 12, Number 1—January 2006
Research
Influenza-associated Deaths in Tropical Singapore
, Stefan Ma*, Ai Ee Ling†, and Suok Kai Chew*
Table 3
Adjusted risk ratios* and p values for each 10% change in positive influenza A and RSV test results, and for each 1% change in positive influenza B† virus test results, 1996–2003‡
| Mortality outcome/risk factor | Adjusted risk ratio (95% CI), p value |
|||||
|---|---|---|---|---|---|---|
| Model 1§ | Model 2 | Model 3 | Model 4 | Model 5 | Model 6 | |
| All-cause deaths | ||||||
| Influenza A | 1.05 (1.04–1.06), 0.000 | – | – | 1.05 (1.04–1.06), 0.000 | 1.05 (1.04–1.06), 0.000 | 1.05 (1.04–1.06), 0.000 |
| Influenza B | – | 1.01 (1.00–1.02), 0.173 | – | 1.01 (1.01–1.02), 0.001 | – | 1.01 (1.01–1.02), 0.001 |
| RSV | – | – | 1.00 (0.99–1.00), 0.810 | – | 1.00 (1.00–1.01), 0.254 | 1.00 (1.00–1.01), 0.159 |
| Underlying P&I deaths | ||||||
| Influenza A | 1.12 (1.08–1.16), 0.000 | – | – | 1.12 (1.08–1.16), 0.000 | 1.13 (1.09–1.17), 0.000 | 1.13 (1.09–1.17), 0.000 |
| Influenza B | – | 0.99 (0.96–1.02), 0.389 | – | 1.00 (0.94–1.03), 0.994 | – | 1.00 (0.98–1.03), 0.872 |
| RSV | – | – | 1.01 (0.99–1.02), 0.342 | – | 1.03 (1.00–1.02), 0.022 | 1.01 (1.00–1.02), 0.021 |
| Underlying C&R deaths | ||||||
| Influenza A | 1.08 (1.06–1.10), 0.000 | – | – | 1.08 (1.07–1.10), 0.000 | 1.08 (1.06–1.11), 0.000 | 1.09 (1.07–1.11), 0.000 |
| Influenza B | – | 1.01 (0.99–1.02), 0.360 | – | 1.02 (1.01–1.03), 0.004 | – | 1.02 (1.01–1.03), 0.002 |
| RSV | – | – | 1.00 (0.99–1.01), 0.686 | – | 1.01 (1.00–1.01), 0.025 | 1.01 (1.00–1.01), 0.011 |
*Risk ratio estimates (95% confidence intervals) of each death category were adjusted for number of days in each month, linear and squared time trends, seasonal patterns, temperature and relative humidity; –, risk factor was not included in model.
†Each 1% change was used for influenza B because of the small range of positive influenza B test results.
‡CI, confidence interval; RSV, respiratory syncytial virus; P&I, pneumonia and influenza; C&R, circulatory and respiratory.
§Negative binomial regression models. Model 1, death outcome = influenza A + confounders; model 2, death outcome = influenza B (FluB) + confounders; model 3, death outcome = RSV + confounders; model 4, death outcome = model 1 + FluB; model 5, death outcome = model 1 +RSV; model 6, death outcome = model 4 + RSV.