Table 3.
Associations between greenspace measures and odds of asthma exacerbation, by case type (odds ratios (OR) and 95% confidence intervals (CI) for interquartile-range (IQR) increase)
| N controls | N cases | Overall greenness (NDVI) | Tree canopy cover (%) | Grass/shrub cover (%) | Impervious surface (%) | |
|---|---|---|---|---|---|---|
| IQR = 0.16 | IQR = 10.2% | IQR = 6.1% | IQR = 14.9% | |||
| All cases | 34,681 | 17,639 | 0.98 (0.93–1.03) | 0.98 (0.95–1.02) | 0.99 (0.96–1.02) | 1.02 (0.98–1.06) |
| Outpatient cases | 15,346 | 7853 | 0.98 (0.92–1.04) | 1.00 (0.96–1.04) | 0.98 (0.94–1.02) | 1.00 (0.95–1.04) |
| ED cases | 10,922 | 5522 | 0.92 (0.85–0.99) | 0.97 (0.93–1.02) | 0.97 (0.92–1.01) | 1.05 (0.99–1.12) |
| Inpatient cases | 8413 | 4264 | 1.08 (0.99–1.17) | 0.96 (0.91–1.02) | 1.02 (0.97–1.08) | 1.02 (0.96–1.10) |
| Not frequent (1/year) | 16,327 | 8323 | 1.02 (0.97–1.08) | 1.03 (0.99–1.06) | 0.99 (0.96–1.03) | 0.98 (0.94–1.03) |
| Frequent (> 1/year) | 18,354 | 9316 | 0.94 (0.88–1.01) | 0.94 (0.90–0.99) | 0.98 (0.94–1.02) | 1.05 (1.00–1.12) |
OR, odds ratio; CI, confidence interval; IQR, interquartile range; NDVI, normalized difference vegetation index
All associations adjusted for calendar month, day-of-week, census tract population density, and census tract SES index