| Aged 30-69 years | Excluding subjects with asthma | ||
---|---|---|---|---|
 | Urban | Rural | Urban | Rural |
Educational level | Â | Â | Â | Â |
   ≥ 12 years | 1 | 1 | 1 | 1 |
   9-11 years | 1.17 (0.91-1.51) | 1.14 (0.84-1.53) | 1.12 (0.86-1.46) | 1.07 (0.79-1.46) |
   < 9 years | 1.62 (1.27-2.06) | 1.61 (1.23-2.12) | 1.59 (1.24-2.05) | 1.60 (1.21-2.12) |
   P for trend | < 0.001 | < 0.001 | < 0.001 | < 0.001 |
Income | Â | Â | Â | Â |
   High | 1 | 1 | 1 | 1 |
   Middle | 1.12 (0.88-1.42) | 0.86 (0.69-1.08) | 1.05 (0.82-1.35) | 0.78 (0.62-0.98) |
   Low | 1.60 (1.25-2.01) | 1.01 (0.82-1.25) | 1.52 (1.17-1.97) | 0.91 (0.73-1.14) |
   P for trend | < 0.001 | 0.466 | < 0.001 | 0.942 |