Premium
Smoking and risk for psoriasis: a population‐based twin study
Author(s) -
Lønnberg Ann Sophie,
Skov Lone,
Skytthe Axel,
Kyvik Kirsten Ohm,
Pedersen Ole Birger,
Thomsen Simon Francis
Publication year - 2016
Publication title -
international journal of dermatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.677
H-Index - 93
eISSN - 1365-4632
pISSN - 0011-9059
DOI - 10.1111/ijd.13073
Subject(s) - medicine , psoriasis , odds ratio , twin study , confidence interval , dizygotic twin , monozygotic twin , population , demography , risk factor , heritability , dermatology , environmental health , genetics , sociology , biology
Background Smoking is a potential risk factor for psoriasis. Both psoriasis and smoking habits are partly explained by genetic factors. However, twin studies investigating the association between these traits are limited. Methods Questionnaire‐based data on smoking habits and psoriasis were collected for 34,781 twins, aged 20–71 years, from the Danish Twin Registry. A co‐twin control analysis was performed on 1700 twin pairs discordant for lifetime history of smoking. Genetic and environmental correlations between smoking and psoriasis were estimated using classical twin modeling. Results After multivariable adjustment, age group (50–71 vs. 20–49 years) and childhood exposure to environmental tobacco smoke ( ETS ) were significantly associated with psoriasis in the whole population (odds ratio [ OR ] 1.15, 95% confidence interval [ CI ] 1.02–1.29 [ P = 0.021] and OR 1.28, 95% CI 1.10–1.49 [ P = 0.002], respectively). Risk for psoriasis increased substantially ( OR 2.18, 95% CI 1.82–2.61; P < 0.001) for smokers with a history of >5 pack‐years, even after adjusting for age, sex, and childhood ETS . Among twin pairs discordant for smoking, risk for psoriasis in the ever‐smoking twin was lower among monozygotic twins ( OR 1.23, 95% CI 0.59–2.56; P = 0.578) than among same‐sex dizygotic twins ( OR 2.21, 95% CI 1.36–3.58; P = 0.001). Genetic factors explained 20% (14–25%; P < 0.001) of the correlation between psoriasis and smoking, whereas non‐shared environmental factors explained 8% (0–22%; P = 0.504). Conclusions Tobacco consumption and childhood ETS are significantly associated with psoriasis. Results indicate shared genetic factors for smoking and psoriasis.