Age and multivariate-adjusted RR for the association between smoking and the risk of PsA with different severity scores among participants with psoriasis*
| Person-years | Scores 47–57 | Multivariate-adjusted RR† (95% CI) | Scores ≥57 | Multivariate-adjusted RR† (95% CI) | |
|---|---|---|---|---|---|
| Reference: never smokers | 2356 | 54 | 1.00 | 22 | 1.00 |
| Smoking status | |||||
| Past smokers | 1191 | 35 | 1.35 (0.78 to 2.35) | 11 | 1.21 (0.51 to 2.87) |
| Current smokers | 805 | 19 | 1.27 (0.68 to 2.39) | 16 | 2.72 (1.15 to 6.42) |
| 1–14 cigarettes/day | 328 | 7 | 0.93 (0.35 to 2.47) | 5 | 1.95 (0.57 to 6.69) |
| ≥15 cigarettes/day | 477 | 12 | 1.55 (0.73 to 3.28) | 11 | 3.48 (1.24 to 9.77) |
| p for trend | 0.146 | 0.017 | |||
| Duration, years | |||||
| <25 | 1680 | 42 | 1.32 (0.80 to 2.19) | 13 | 1.15 (0.50 to 2.62) |
| ≥25 | 316 | 12 | 1.30 (0.61 to 2.79) | 14 | 4.29 (1.65 to 11.18) |
| p for trend | 0.259 | 0.005 | |||
| Pack-years | |||||
| <20 | 1453 | 33 | 1.19 (0.69 to 2.03) | 11 | 0.94 (0.38 to 2.30) |
| ≥20 | 543 | 21 | 1.61 (0.85 to 3.06) | 16 | 3.86 (1.62 to 9.19) |
| p for trend | 0.592 | 0.030 | |||
↵* PsA cases were classified into two groups by the cutoff of scores at 57, picked to include those with the top third of the scores into one category.
↵† Adjusted for age (continuous variable), body mass index (<18.5, 18.5–24.9, 25–29.9, 30–34.9 or ≥35 kg/m2), alcohol drinking (no, <4.9, 5.0–9.9, 10–14.9, 15–29.9 or ≥30.0 g/day), vigorous physical activity (metabolic equivalent h/week, in quintiles).
PsA, psoriatic arthritis.