1. ^*Centro Studi GISED, Ospedali Riuniti di Bergamo, Bergamo, Italy;
2. ^†Istituto di Ricerche Farmacologiche Mario Negri, Milan, Italy;
3. ^‡Clinica Dermatologica, Università di Padova, Padus, Italy;
4. ^§Clinica Dermatologica, Università di Ferrara, Ferrara, Italy;
5. ^¶Clinica Dermatologica, Università di Terni, Italy;
6. Ospedale Principale Militare Taranto, Italy;
7. ^**U.O. Dermatologia, Azienda USL 4, Prato, Italy;
8. ^††Clinica Dermatologica, Università di Torino, Turin, Italy;
9. ^‡‡Clinica Dermatologica, Università di Verona, Verona, Italy;
10. ^§§U.O. Dermatologia, Ospedale di Cremona, Cremona, Italy;
11. ^¶¶U.O.Dermatologia, Ospedale Bufalini, Cesena, Italy;
12. Dipartimento di Dermatologia, Ospedale San Raffaele, Milan, Cremona, Italy;
13. ^***Clinica Dermatologica, Ospedale San Paolo, Milan, Italy;
14. ^†††Clinica Dermatologica, Università di Firenze, Florence, Italy;
15. ^‡‡‡U.O. Dermatologia, Ospedale di Savona, Savona, Italy;
16. ^§§§U.O. Dermatologia, Dipartimento di Scienza della Salute, Università di Genova, Genoa, Italy;
17. ^¶¶¶Istituto di Statistica Medica e Biometria, Università degli Studi di Milano, Milan, Italy

Correspondence: Dr Luigi Naldi, Centro Studi GISED, Ospedali Riuniti, L.go Barozzi 1, 24100 Bergamo, Italy. Email: luigi.naldi@gised.it

Received 1 September 2004; Revised 16 December 2004; Accepted 20 December 2004.

Abstract

We conducted a case–control study to analyse the association of psoriasis of recent onset with smoking habits, body mass index (BMI) and stressful life events. Cases (n=560; median age 38) were patients with a first diagnosis of psoriasis and a history of skin manifestations of no longer than two years after the reported disease onset. Patients with a new diagnosis of skin diseases other than psoriasis (n=690; median age 36) were selected as controls. The risk of psoriasis was higher in ex- and current smokers than in never-smokers, the relative risk estimates (OR) being 1.9 for ex-smokers and 1.7 for smokers. Smoking was strongly associated with pustular lesions (32 patients, OR=5.3 for smokers). The frequency of psoriasis varied significantly in relation to a family history of psoriasis in first degree relatives, BMI (OR=1.6 and 1.9 for over weighted, BMI 26–29, and obese, BMI 30, respectively) and stressful life event score (compared to the lower index quartile, the OR being 2.2 for index values 115). Risk estimates, when taking into consideration the combined effect of these factors with smoking habits, were consistent with a multiplicative model of risk combination with no significant statistical interaction.