Table 4 Adjusted and unadjusted Cox proportional hazard model risk ratio for death with 95% confidence intervals. Adjusted for initial FEV1, change in weight, initial age, height.
| n | Not adjusted | Adjusted | ||
|---|---|---|---|---|
| Deaths, n | RR (95% CI) | RR (95% CI) | ||
| (A) Entire cohort (n = 1730) | ||||
| <30 ml/year | 580 | 78 | 1.00 | 1.00 |
| 30 to <60 ml/year | 688 | 99 | 1.07 (0.80 to 1.44) | 1.13 (0.84 to 1.52) |
| 60 to <90 ml/year | 300 | 61 | 1.40 (1.00 to 1.96) | 1.39 (0.99 to 1.97) |
| ⩾90 ml/year | 162 | 47 | 2.05 (1.42 to 2.94) | 1.90 (1.32 to 2.76) |
| (B) Never smokers (n = 327) | ||||
| <30 ml/year | 151 | 17 | 1.00 | 1.00 |
| 30 to <60 ml/year | 116 | 14 | 1.08 (0.53 to 2.19) | 1.45 (0.70 to 3.04) |
| 60 to <90 ml/year | 37 | 7 | 1.56 (0.64 to 3.78) | 3.31 (1.16 to 8.31) |
| ⩾90 ml/year | 23 | 5 | 1.72 (0.63 to 4.69) | 3.34 (1.12 to 9.98) |
| (C) Current and former smokers (n = 1403) | ||||
| <30 ml/year | 429 | 61 | 1.00 | 1.00 |
| 30 to <60 ml/year | 572 | 85 | 1.04 (0.75 to 1.45) | 1.11 (0.80 to 1.55) |
| 60 to <90 ml/year | 263 | 54 | 1.33 (0.92 to 1.92) | 1.28 (0.88 to 1.87) |
| ⩾90 ml/year | 139 | 42 | 2.03 (1.37 to 3.00) | 1.82 (1.22 to 2.71) |
| (D) No obstructive or restrictive pattern at first survey (n = 1198) | ||||
| <30 ml/year | 386 | 42 | 1.00 | 1.00 |
| 30 to <60 ml/year | 492 | 62 | 1.17 (0.79 to 1.74) | 1.24 (0.83 to 1.84) |
| 60 to <90 ml/year | 216 | 42 | 1.64 (1.07 to 2.52) | 1.64 (1.05 to 2.56) |
| ⩾90 ml/year | 104 | 27 | 2.16 (1.33 to 3.51) | 2.15 (1.31 to 3.54) |
US, National Study of Coal Workers' Pneumoconiosis, 1969–97.