Table 2.
Stratified analyses of association [OR (95% CI)] between daily maximum O3 exposures and appendicitis cases in 12 cities of Canada (2004–2008).
| Modela | n | Same-day | 1-day lag | Cumulative average daily maximum O3 concentration (IQR = 16 ppb) | ||
|---|---|---|---|---|---|---|
| 3-day average | 5-day average | 7-day average | ||||
| All appendicitis | 35,811 | 1.00 (0.96, 1.04) | 1.03 (1.00, 1.11) | 1.03 (0.99, 1.08) | 1.04 (0.99, 1.10) | 1.07 (1.02, 1.13) |
| Appendicitis phenotype | ||||||
| Nonperforated | 24,730 | 1.00 (0.95, 1.06) | 1.01 (0.97,1.05) | 1.00 (0.94, 1.06) | 0.99 (0.92, 1.07) | 1.02 (0.95, 1.09) |
| Perforated | 11,081 | 0.98 (0.93, 1.04) | 1.07 (1.01, 1.14) | 1.11 (1.01, 1.23) | 1.15 (1.04, 1.27) | 1.22 (1.09, 1.36) |
| Age (years) | ||||||
| ≤ 20 | 10,313 | 0.93 (0.88, 0.99) | 0.97 (0.92, 1.02) | 0.96 (0.88, 1.04) | 1.00 (0.90, 1.11) | 1.06 (0.96, 1.17) |
| 21–39 | 13,474 | 1.00 (0.95, 1.05) | 1.05 (1.00, 1.10) | 1.04 (0.97, 1.11) | 1.06 (0.98, 1.14) | 1.08 (0.99, 1.18) |
| ≥ 40 | 12,024 | 1.06 (0.97, 1.16) | 1.05 (1.00, 1.11) | 1.09 (1.01, 1.17) | 1.06 (0.98, 1.15) | 1.08 (0.99, 1.19) |
| Sex | ||||||
| Male | 19,509 | 0.99 (0.95, 1.04) | 1.03 (0.99, 1.07) | 1.03 (0.98, 1.09) | 1.04 (0.98, 1.11) | 1.05 (0.98, 1.13) |
| Female | 16,302 | 1.00 (0.95, 1.06) | 1.02 (0.98, 1.07) | 1.03 (0.96, 1.10) | 1.05 (0.95, 1.16) | 1.11 (1.00, 1.22) |
| Season (all appendicitis) | ||||||
| Spring | 8,991 | 0.99 (0.91, 1.07) | 1.01 (0.95, 1.07) | 0.97 (0.89, 1.06) | 0.96 (0.87, 1.06) | 0.99 (0.89, 1.11) |
| Summer | 9,504 | 0.96 (0.90, 1.02) | 0.99 (0.94, 1.05) | 1.02 (0.95, 1.10) | 1.07 (0.98, 1.16) | 1.08 (0.97, 1.21) |
| Autumn | 9,038 | 0.99 (0.89, 1.10) | 1.05 (0.98, 1.12) | 1.04 (0.93, 1.16) | 1.03 (0.92, 1.16) | 1.08 (0.96, 1.22) |
| Winter | 8,278 | 1.06 (0.98, 1.15) | 1.08 (1.00, 1.17) | 1.11 (1.00, 1.23) | 1.07 (0.95, 1.20) | 1.10 (0.95, 1.28) |
| Season (perforated appendicitis) | ||||||
| Spring | 2,668 | 1.04 (0.91, 1.18) | 1.03 (0.87, 1.22) | 1.10 (0.94, 1.29) | 1.12 (0.93, 1.34) | 1.19 (0.97, 1.46) |
| Summer | 2,899 | 0.88 (0.79, 0.99) | 0.99 (0.89, 1.09) | 1.01 (0.88, 1.16) | 1.12 (0.96, 1.30) | 1.21 (1.02, 1.44) |
| Autumn | 2,879 | 0.95 (0.81, 1.11) | 1.14 (1.01, 1.28) | 1.16 (0.95, 1.42) | 1.19 (0.93, 1.51) | 1.28 (0.96, 1.71) |
| Winter | 2,635 | 1.05 (0.92, 1.21) | 1.13 (0.97, 1.32) | 1.13 (0.93, 1.38) | 1.09 (0.82, 1.45) | 1.09 (0.77, 1.55) |
| O3 + NO2 (all appendicitis) | 34,335 | 1.01 (0.97, 1.05) | 1.02 (0.99, 1.06) | 1.04 (0.99, 1.09) | 1.06 (1.01, 1.11) | 1.08 (1.02, 1.14) |
| O3 + NO2 (perforated appendicitis) | 10,736 | 1.01 (0.94, 1.08) | 1.07 (1.00, 1.14) | 1.13 (1.02, 1.25) | 1.15 (1.04, 1.27) | 1.17 (1.07, 1.28) |
| O3 + PM2.5 (all appendicitis) | 34,335 | 1.01 (0.97, 1.04) | 1.02 (0.99, 1.06) | 1.03 (0.99, 1.08) | 1.03 (0.98, 1.09) | 1.06 (1.00, 1.13) |
| O3 + PM2.5 (perforated appendicitis) | 10,736 | 1.00 (0.94, 1.06) | 1.06 (1.00, 1.13) | 1.09 (0.99, 1.20) | 1.10 (1.00, 1.20) | 1.12 (1.02, 1.23) |
| Perforated appendicitis defined only by diagnostic codeb | 13,014 | 1.06 (0.94, 1.07) | 1.08 (1.02, 1.14) | 1.12 (1.02, 1.24) | 1.14 (1.04, 1.25) | 1.20 (1.08, 1.33) |
| Halifax excluded | ||||||
| All appendicitis | 34,335 | 1.01 (0.97, 1.04) | 1.03 (1.00, 1.06) | 1.04 (1.00, 1.08) | 1.05 (1.00, 1.10) | 1.08 (1.02, 1.14) |
| Perforated appendicitis | 10,736 | 0.99 (0.93,1.05) | 1.08 (1.01, 1.15) | 1.12 (1.01, 1.25) | 1.15 (1.03, 1.29) | 1.21 (1.08, 1.35) |
| aConditional logistic regression estimated the odds of appendicitis in association with a 16-ppb increase in the daily maximum O3 concentration adjusted for mean temperature and relative humidity on the same day as admission for appendicitis. bOriginal definition includes an ICD-10-CA diagnostic code for appendicitis and a procedural code for appendectomy. | ||||||