Table 3

The association between smoking status and PsA* (N=654) compared with psoriasis alone (N=401) by logistic regression analysis, adjusted for age, sex, level of education, alcohol consumption, duration and severity of psoriasis

	Univariate model			Multivariate model
Covariate	OR	95% CI	p Value	OR	95% CI	p Value
Smoking status
Current vs life-time non- smokers	0.66	0.48 to 0.90	0.009	0.57	0.41 to 0.81	0.002
Past vs life-time non- smokers	0.63	0.46 to 0.84	0.002	0.81	0.56 to 1.12	0.21
Age group, years^†
31–40	0.42	0.28 to 0.62	<0.0001	0.49	0.33 to 0.75	0.0009
41–50	0.34	0.23 to 0.51	<0.0001	0.43	0.28 to 0.65	<0.0001
51–60	0.14	0.09 to 0.22	<0.0001	0.18	0.11 to 0.28	<0.0001
>60	0.10	0.06 to 0.17	<0.0001	0.06	0.07 to 0.23	<0.0001
Sex: male vs female	0.91	0.71 to 1.17	0.47	1.03	0.78 to 1.36	0.85
Duration of psoriasis, years^‡
6–10	0.85	0.58 to 1.25	0.41	0.70	0.47 to 1.06	0.09
11–15	0.66	0.43 to 1.02	0.06	0.49	0.31 to 0.79	0.003
16–20	0.45	0.28 to 0.70	0.0005	0.46	0.28 to 0.74	0.002
21 and more	0.26	0.19 to 0.37	<0.0001	0.37	0.26 to 0.53	<0.0001
Alcohol consumption
Social vs none	0.92	0.69 to 1.22	0.55	0.94	0.68 to 1.28	0.67
Daily vs none	1.17	0.74 to 1.84	0.50	1.65	0.99 to 2.76	0.05
Severe psoriasis: yes vs no	2.13	1.56 to 2.91	<0.0001	2.07	1.47 to 2.92	<0.0001

↵* Psoriatic arthritis (PsA) is the outcome variable.
↵† Age at the time of the diagnosis for PsA and at first study visit for psoriasis. The reference group is 30 years and younger.
↵‡ Duration of psoriasis at the time of the diagnosis of PsA (for PsA) and at first study visit (for psoriasis). The reference group is 5 years and less