Table 2. Characteristics of Lower Respiratory Infection Cases and Controls and Their Mothersa.
| cases | controls | ||
|---|---|---|---|
| N = 14052b | N = 84739 | p-valuec | |
| mean (SD) of average weekly PM2.5 during pregnancy (μg/m3) | 8.0 (2.1) | 7.9 (2.0) | p < 0.001 |
| mean (SD) of maximum 1-week PM2.5 during pregnancy (μg/m3) | 28.8 (28.8) | 27.9 (27.6) | p < 0.001 |
| mean (SD) PM2.5 in first year of life (μg/m3) | 8.3 (2.6) | 8.3 (2.3) | p = 0.047 |
| mean (SD) temperature during pregnancy (°C) | 8.7 (3.6) | 8.7 (3.5) | p = 0.007 |
| Infant sex (%) | |||
| female | 42.0% | 50.1% | p < 0.001 |
| male | 58.0% | 49.9% | |
| other | 0% | <0.1% | |
| Maternal neighborhood SES quintile (%) | |||
| first (most deprived) | 21.8% | 21.1% | P = 0.082 |
| second | 21.0% | 21.1% | |
| third | 20.1% | 20.8% | |
| fourth | 20.8% | 21.3% | |
| fifth (least deprived) | 14.8% | 14.3% | |
| missing | 1.4% | 1.4% | |
| mean (SD) maternal age at birth (years) | 31.5 (5.2) | 31.9 (5.0) | p < 0.001 |
| Maternal BMI category (%) | |||
| underweight | 3.7% | 4.3% | p < 0.001 |
| normal | 41.1% | 45.9% | |
| overweight | 19.4% | 18.6% | |
| obese | 14.4% | 11.7% | |
| missing | 21.3% | 19.5% | |
| Maternal smoking (%) | |||
| current smoker | 6.6% | 4.5% | p < 0.001 |
| former smoker | 7.9% | 6.9% | |
| never smoked | 85.5% | 88.6% | |
| Newborn feeding (%) | |||
| exclusive breast milk | 31.6% | 29.4% | p < 0.001 |
| breast milk and formula | 64.2% | 67.7% | |
| formula | 3.1% | 1.9% | |
| missing | 1.2% | 0.9% |
a
Subjects were prenatally exposed to wildfire seasons from 2016 to 2019 and matched on geography and epidemiologic week of birth.
b
3154 infants were dispensed amoxicillin after being diagnosed with lower respiratory infection.
c
A two-sample t test was used to compare continuous variables, a χ-square test was used to compare categorical variables when all expected cell counts were ≥5, and Fisher’s exact test was used when any expected cell counts were <5 for the covariates in cases and controls.