Table 1. Characteristics of Otitis Media Cases and Controls and Their Mothersa.
| cases | controls | ||
|---|---|---|---|
| N = 9187b | N = 69858 | p-valuec | |
| mean (SD) of average weekly PM2.5 during pregnancy (μg/m3) | 8.1 (2.1) | 8.0 (2.0) | p < 0.001 |
| mean (SD) of maximum 1-week PM2.5 during pregnancy (μg/m3) | 30.1 (29.5) | 28.0 (28.2) | p < 0.001 |
| mean (SD) PM2.5 in first year of life (μg/m3) | 8.5 (2.3) | 8.3 (2.1) | p < 0.001 |
| mean (SD) temperature during pregnancy (°C) | 8.0 (3.8) | 8.5 (3.7) | p < 0.001 |
| Infant sex (%) | |||
| female | 43.6% | 50.2% | p < 0.001 |
| male | 56.4% | 49.8% | |
| other | 0% | <0.1% | |
| Maternal neighborhood SES quintile (%) | |||
| first (most deprived) | 20.7% | 20.5% | P = 0.201 |
| second | 21.2% | 21.3% | |
| third | 20.5% | 20.7% | |
| fourth | 20.9% | 21.7% | |
| fifth (least deprived) | 15.3% | 14.6% | |
| missing | 1.4% | 1.3% | |
| mean (SD) maternal age at birth (years) | 31.2 (5.2) | 31.8 (5.0) | p < 0.001 |
| Maternal BMI category (%) | |||
| Underweight | 3.3% | 4.1% | p < 0.001 |
| Normal | 41.0% | 45.6% | |
| Overweight | 20.0% | 19.0% | |
| Obese | 15.6% | 12.2% | |
| Missing | 20.3% | 19.1% | |
| Maternal smoking (%) | |||
| current smoker | 6.4% | 4.9% | p < 0.001 |
| former smoker | 8.3% | 7.1% | |
| never smoked | 85.2% | 88.0% | |
| Newborn feeding (%) | |||
| exclusive breast milk | 30.2% | 29.6% | P = 0.007 |
| breast milk and formula | 66.0% | 67.3% | |
| formula | 2.5% | 2.1% | |
| missing | 1.2% | 1.0% |
a
Subjects were prenatally exposed to wildfire seasons from 2016 to 2019 and matched on geography and epidemiologic week of birth.
b
6345 infants were dispensed amoxicillin after being diagnosed with otitis media.
c
A two-sample t test was used to compare continuous variables, a chi-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.