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Association of Early-Stage Psoriasis With Smoking and Male ...


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Association of Early-Stage Psoriasis With Smoking and Male ...

  1. 1. Association of Early-Stage Psoriasis With Smoking and Male Alcohol Consumption Evidence From an Italian Case-Control Study Luigi Naldi, MD; Lorenzo Peli, MD; Fabio Parazzini, MD; and the Psoriasis Study Group of the Italian Group for Epidemiologic Research in Dermatology Objective: To analyze the association of psoriasis with smoking habits and alcohol consumption before first di- agnosis by a dermatologist. Design: A multicenter case-control study. Interviews were conducted by trained medical investigators using a structured questionnaire. Setting: Outpatient services of 10 general and 10 teach- ing hospitals in northern and southern Italy. Subjects: Patients with a first diagnosis of psoriasis made by a dermatologist and a history of skin manifes- tations of no longer than 2 years after the reported dis- ease onset. Patients with new diagnoses of skin diseases other than psoriasis were selected as control subjects. A total of 404 case patients (median age, 35 years) and 616 controls (median age, 36 years) were included in the analysis. Results: The risk for psoriasis was higher in ex- smokers and in current smokers than in patients who never smoked. The relation with smoking was stronger and more consistent among women than men. In men, a significant association was restricted to the ex-smoker status. Smoking was strongly associated with pustular le- sions (29 patients) with an adjusted odds ratio of 10.5 (95% confidence interval, 3.3-33.5) for those smoking more than 15 cigarettes per day. No significant overall association with alcohol consumption was documented after controlling for smoking habits. However, the risk seemed to vary according to sex, with a moderate asso- ciation being documented in men. Conclusions:Cigarettesmokingand,inmen,alcoholcon- sumption are associated with psoriasis. There is a strong association between smoking and pustular lesions. Arch Dermatol. 1999;135:1479-1484 T HE INTERACTION between genetic and environmen- tal factors, ie, multifacto- rial heredity, seems to play a role in the causes of pso- riasis. Several studies exploring environ- mental factors have considered smoking habits and alcohol consumption, but their results have been discordant. Smoking has been found to be more frequent among pa- tients with psoriasis than among control subjects before the disease onset or the first dermatological diagnosis in some but not all studies. Similar discordant data con- cern alcohol consumption.1-8 Variations by sex have been suggested, with smoking being more strongly associated with pso- riasis among women and alcohol con- sumption among men.4,8 Palmoplantar pustulosis, a disease related to psoriasis, has also been found to correlate strongly with smoking habits, but whether a simi- lar degree of association applies to other varieties of pustular psoriasis remains un- clear.9 The widespread use of alcohol and cigarettes, the disabling nature of psoria- sis, and the lack of effective and safe treat- ments for the disease justify efforts to fur- ther our understanding of these issues. We herein present a case-control study involving patients with newly diag- nosed psoriasis and controls with newly diagnosed dermatological conditions other than psoriasis. Our aims were to analyze the association of psoriasis at an early- stage with common environmental fac- tors, such as smoking and alcohol con- sumption, and to explore the existence of variations in selected subgroups. RESULTS The distribution of case patients and con- trols according to age, sex, marital status, occupation, family history of psoriasis in first-degree relatives, BMI, and coffee con- sumption is reported in Table 1. The me- dian age at diagnosis was 35 years in case patients and 36 years in controls. A total of 248 case patients (61.4%) reported on- STUDY From the Department of Dermatology, Universita` degli Studi di Milano, Ospedali Riuniti di Bergamo (Drs Naldi and Peli), and the Istituto di Ricerche Farmacologiche “Mario Negri” (Dr Parazzini), Milano Italy. A complete list of the members of the Psoriasis Study Group of the Italian Group for Epidemiologic Research in Dermatology appears in a box on page 1484. ARCH DERMATOL/VOL 135, DEC 1999 WWW.ARCHDERMATOL.COM 1479 ©1999 American Medical Association. All rights reserved. on November 10, 2010www.archdermatol.comDownloaded from
  2. 2. set before 39 years of age. There was a significantly higher proportion of male subjects in the case compared with the control group. No association was documented be- tween marital status or occupation and psoriasis. As ex- pected, the risk for psoriasis was higher in those report- ing a family history of the disease. The age- and sex- adjusted OR was 7.9 (95% CI, 4.7-13.3) for subjects who reported a history of the disease in parents, whereas the OR adjusted for age, sex, and number of siblings was 3.7 (95% CI, 2.4-5.8) for subjects reporting a history of the disease in siblings. Body mass index was also associated with psoriasis. Compared with a BMI of lower than 22.0, the age- and sex-adjusted OR was 1.3 (95% CI, 1.0-1.8) for a BMI of 22.0 to 26.0 and 1.9 (95% CI, 1.4-2.6) for a BMI of greater than 26.0. No association was observed between coffee consumption and psoriasis. Table 2 shows the distribution of case patients and controls according to smoking habits and alcohol con- sumption. The OR of having psoriasis was higher in pre- vious and current smokers. Compared with people who SUBJECTS AND METHODS PARTICIPANTS The study was conducted in Italy within the framework of the Italian Group for Epidemiologic Research in Derma- tology.7 The outpatient services of 10 teaching hospitals and 10 general hospitals in northern and southern Italy par- ticipated. Entry criteria for patients with psoriasis were as fol- lows: a first diagnosis of psoriasis made by a dermatologist and a history of skin manifestations of no longer than 2 years after the reported disease onset. The onset was considered to be the date an individual first became aware of the clinical manifestations attributable to psoriasis. The definition of on- set was guided by a thorough inquiry into the timing of rel- evant signs and symptoms. For inclusion, at least 1 typical plaque of psoriasis, ie, a fixed, well-demarcated erythema- tous scaly patch, was required; however, most patients pre- sented with diffuse manifestations leading to a straightfor- ward clinical diagnosis by the specialist. Cases of psoriasis guttata and pustular psoriasis were excluded if they were not associated with a typical plaque of psoriasis. Erythrodermic psoriasis was not considered because of its rarity and the di- agnostic difficulties. All eligible patients who were seen con- secutively during the study period were invited to partici- pate. As controls, we selected subjects with newly diagnosed dermatologicalconditionsotherthanpsoriasiswhowereseen in the same outpatient services as the case patients. Patients with skin conditions regularly associated with alcohol con- sumption or liver disorders were excluded (ie, presenting symptoms of porphyria cutanea tarda, cutaneous manifesta- tions of hemochromatosis and cirrhosis, pellagra, and zinc deficiency syndrome).About1%ofthesuitablecontrolswere excluded because of these conditions. The controls were the first eligible dermatological patients observed on randomly selected days in the 2 weeks following the selection of case patients. Initially, 2 controls per case patient were selected. Subsequently, however, because of the difficulties experi- enced in recruitment, inclusion was limited to 1 control per case patient. Controls were age-matched to case patients in decade categories, and the inclusion of case patients and con- trols was limited to subjects aged 16 through 70 years. Oral informed consent was obtained from each subject, and fewer than 2% of the eligible subjects refused to participate. The study was conducted during the following 3 sepa- rate periods: from January 1, 1988, through August 31, 1990; from January 1 through December 31, 1993; and from April 1, 1996, through October 31, 1997. During the first pe- riod, the study was restricted to 6 centers in northern Italy. Subsequently, an additional 14 centers participated, in- cluding 6 from the southern part of the country. The results of the 3 phases of the study were comparable, and no important differences among the participating centers were observed. A total of 404 case patients with psoriasis, satisfy- ing our entry criteria, and 616 controls were recruited. The psoriasiscaseswereclassifiedasordinarychronicplaquepso- riasis(324[80.2%]),guttatapsoriasisassociatedwithchronic plaque psoriasis (30 [7.4%]), pustular psoriasis, mostly rep- resented byso-calledpsoriasiswithpustules(29 [7.2%]),and mainly flexural psoriasis (21 [5.2%]). None of the patients in this last group had evidence of contact allergy. Diagnoses in the control group included eczema (154 [25.0%]), skin cancers (101 [16.4%]), urticaria (86 [13.9%]), skin infec- tions (81 [13.1%]), pityriasis rosea (62 [10.1%]), and a va- riety of other skin diseases (132 [21.4%]). Informationregardingsociodemographicfactors,smok- ing habits, alcohol consumption, coffee and tea consump- tion, consumption of selected dietary factors, family history of psoriasis in first-degree relatives (ie, parents and sib- lings), and personal medical history was obtained from case patients and controls by trained investigators using a struc- tured questionnaire. Anthropometric measures, including height and weight, were also recorded. Information on smok- ing and alcohol consumption was obtained through a life- time inquiry, including age at onset, average and maximum daily consumption, kind of consumption, and existence of periods of abstinence. The questionnaire used has been vali- dated in Italian epidemiological studies.10 The interviewers hadbiomedicaltrainingandexperienceinmedicalinterview- ing. We computed the average consumption of alcohol per day,assumingacomparablepurealcoholcontentineachtype of drink (that is, 120 mL of wine, 330 mL of beer, 40 mL of spirits, or 12-13 g of pure alcohol).11 A period of abstinence ofatleast6monthsbeforethedateofdiagnosiswasrequested for a patient to be classified as an ex-smoker or ex-drinker. DATA ANALYSIS For each variable, we computed the odds ratios (ORs) of having psoriasis as estimates of relative risks and the cor- responding 95% confidence intervals (CIs). Initially, estimates were obtained from data stratified by age and sex, when appropriate, according to the Mantel- Haenszel method.12 The significance of the linear trend in risk was assessed using the Mantel test.13 Subsequently, to account for the effects of potentially confounding factors, unconditional multiple logistic regression analysis with maximum likelihood fitting was used.14 The regression equa- tions included terms for age, sex, calendar year at inter- view, marital status, occupation, history of psoriasis in first- degree relatives, body mass index (BMI; calculated as weight in kilograms divided by the square of height in meters), smoking habits, and alcohol and coffee consumption. ARCH DERMATOL/VOL 135, DEC 1999 WWW.ARCHDERMATOL.COM 1480 ©1999 American Medical Association. All rights reserved. on November 10, 2010www.archdermatol.comDownloaded from
  3. 3. had never smoked, the Mantel-Haenszel adjusted ORs for ex-smokers was 1.9 (95% CI, 1.3-2.7); for subjects cur- rently smoking up to 15 cigarettes per day, 1.5 (95% CI, 1.1-2.1); for those smoking 16 to 24 cigarettes per day, 1.8 (95%CI,1.2-2.7);andforthosesmokingmorethan24ciga- rettesperday,2.4(95%CI,1.3-4.3).MultivariateORswere consistent with those adjusted for age and sex. Interest- ingly, the risk for psoriasis decreased fairly smoothly with increased duration of smoking habits. Moreover, in ex- smokers, the risk tended to decrease with the increase in time since quitting smoking and to increase with the num- ber of cigarettes smoked per day (data not shown). Case patients tended to report drinking alcohol more frequently than controls. The correlation between alco- hol consumption and smoking was weak (Spearman cor- relation coefficient, 0.24), and after adjusting for smok- ing and other potential confounders, the risk estimates were closer to 1. Ex-drinkers were not at an increased risk for psoriasis, and no relation between the duration of drinking habits and psoriasis was documented. Table 3 presents OR estimates for smoking and al- cohol consumption stratified by sex. The ex-smoker sta- tus was a risk factor among men but not women. As for current smokers, the association was stronger in women than in men, for whom risk estimates appeared even con- sistent with no effect at all. At variance with these find- ings, in women no relation of psoriasis with alcohol con- sumption was documented, whereas an association was documented in men with a dose-response relationship. Table 4 presents OR estimates for smoking and alco- hol consumption according to the clinical variety of pso- riasis. A particularly strong association was docu- mented between smoking and pustular psoriasis, but not between alcohol consumption and pustular psoriasis. We also examined smoking and alcohol consumption ac- cording to age at diagnosis (Յ35 vs Ͼ35 years) and his- tory of psoriasis in first-degree relatives (present vs ab- sent). No important variations were documented except for somewhat higher estimates of ORs for previous and current smoking status in the younger patients com- pared with the older ones (data not presented). COMMENT Some lines of evidence have suggested relations between psoriasis and smoking habits and alcohol consumption, pointing to a possible sex difference. A number of other diseases that are strongly linked with smoking in the gen- eralpopulation,includingcardiovasculardiseases,15,16 Crohn disease,17 lung cancer, tumors of the upper airways,18,19 and kidney cancer,18-20 are associated with psoriasis. Some of theseassociationshavebeenfoundonlyinwomen.16,20 Also, livercirrhosishasbeenlinkedwithpsoriasis.16,21 Intheonly incidence study of psoriasis we are aware of, the smoking profile for male patients was similar to that from a ran- dom sample of the general population, whereas female pa- tients smoked more than women in the general popula- tion. Incident cases were defined as cases newly diagnosed at the Mayo Clinic facilities, which cover the whole Roch- ester, Minn, population.5 In a case-control study of pal- moplantar pustulosis, a condition related to psoriasis and largely predominant in women, the OR in smokers was around 7 (99% CI, 3.9-13.2), and no association with al- cohol consumption was documented.9 Other case-control studies of plaque psoriasis have yielded less striking re- sults.4,6-8 However, in 2 case-control studies from Finland conducted separately in men and women, alcohol con- sumption before the disease onset was associated with pso- riasis among young men, whereas smoking was associ- ated with psoriasis among women.4,8 Our study confirmed that smoking is associated with psoriasis with a dose-response relationship. The asso- ciation was stronger and more consistent among women than men and was also particularly strong for pustular lesions. In addition, we found some evidence pointing to an association with alcohol consumption in men. We should sound a note of caution on some limita- tions of our study. Our case patients received a first diag- nosisofpsoriasisbyadermatologist.Ahistoryofskinmani- festations of no longer than 2 years before the date of the dermatological diagnosis was required. Our aim was to re- strict the assessment to recently developed cases that were reliably evaluated by a specialist. To avoid including inde- terminate or borderline cases, the presence of a typical Table 1. Distribution of Case Patients and Controls According to Age, Sex, Marital Status, Occupation, Family History of Psoriasis, Body Mass Index, and Coffee Consumption No. (%) ␹2 Test for Homogeneity* (P) Case Patients Controls Age, y Ͻ20 67 (16.6) 109 (17.7) 20-39 157 (38.9) 266 (43.2) 5.4 (.14) 40-59 140 (34.6) 173 (28.1) Ն60 40 (9.9) 68 (11.0) Sex Male 219 (54.2) 291 (47.2) 3.6 (.05) Female 185 (45.8) 325 (52.8) Marital status Never married 157 (38.9) 262 (42.5) Married 219 (54.2) 312 (50.7) 0.2 (.90) Divorced or widowed 28 (6.9) 42 (6.8) Occupation Manual 91 (22.5) 169 (27.4) Clerical 143 (35.4) 205 (33.3) 3.3 (.34) Professional 19 (4.7) 31 (5.0) Others 151 (37.4) 211 (34.3) Family history of psoriasis† No 291 (72.2) 574 (93.2) 92.6 (Ͻ.001) Yes 113 (27.8) 42 (6.8) Body mass index, kg/m2 ‡ Ͻ22.0 103 (25.6) 214 (34.7) 22.0-26.0 159 (39.4) 247 (40.1) 12.7 (.001) Ͼ26.0 141 (35.0) 155 (25.2) Coffee consumption Never or occasional 91 (22.5) 136 (22.1) 1-2 cups per day 181 (44.8) 272 (44.1) 0.04 (.90) Ն3 cups per day 132 (32.7) 208 (33.8) *The degree of freedom is equal to the number of categories minus 1. †Includes parents or siblings. ‡Information was missing for 1 case patient. 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  4. 4. plaque of psoriasis was required. However, no satisfactory criteria are available for standardizing the diagnosis of pso- riasis in clinical and epidemiological studies.22 The choice of dermatological controls was dictated mainly by the need to control for the reasons leading to specialist consultation. Usually it is stated that studies with controls with disease at the same organ level as the case patients may result in overmatching.14 This is a rather protective bias, and we tried to minimize it by ex- cluding skin manifestations regularly associated with alcohol consumption or liver diseases. These repre- sented a small proportion of all the eligible controls. We matched for age but not sex, and there was a difference in the distribution of this variable among case patients and controls. However, we adjusted all our analyses, whenever indicated, for sex and examined risks in stratification by sex. Our decision to use the index date as the date of the first diagnosis by a specialist may be questionable, a major problem being the inability to separate exposures that pre- cede from those that follow clinical onset. We acknowl- edge that there are difficulties involved in defining the real onset of a disease like psoriasis, which may slowly evolve from mild nonspecific signs (eg, dandruff) to overt clini- Table 2. Distribution of Case Patients and Controls According to Smoking and Alcohol Consumption* Case Patients Controls Odds Ratio (95% Confidence Interval) M-H† ␹2 for Trend (P)‡ MLR§ ␹2 for Trend (P)‡ Never smoked 154 (38.1) 318 (51.6) 1࿣ 1࿣ Former smokers 75 (18.5) 83 (13.5) 1.9 (1.3-2.7) 1.8 (1.2-2.6) Smokers, cigarettes per day Յ15 95 (23.5) 130 (21.1) 1.5 (1.1-2.1) 1.4 (1.0-2.0) 16-24 56 (13.9) 64 (10.4) 1.8 (1.2-2.7) 15.1 (Ͻ.001) 1.7 (1.1-2.7) 13.2 (Ͻ.001) Ն25 24 (5.9) 21 (3.4) 2.4 (1.3-4.3) 2.1 (1.1-3.9) Duration of smoking habits, y Ͻ5 31 35 1.8 (1.1-3.0) 1.8 (1.1-3.0) 5-14 47 57 1.7 (1.1-2.5) 6.4 (.01) 1.6 (1.1-2.6) 4.8 (.02) Ն15 97 123 1.5 (1.1-2.1) 1.5 (1.1-2.2) Nondrinkers 94 (23.3) 167 (27.1) 1࿣ 1࿣ Former drinkers 12 (3.0) 21 (3.4) 1.1 (0.5-2.4) 0.8 (0.4-1.7) Drinkers, drinks per day Յ1 97 (24.0) 185 (30.0) 0.9 (0.6-1.3) 0.8 (0.6-1.2) 2-4 127 (31.4) 168 (27.3) 1.3 (0.9-1.8) 3.12 (.07) 1.2 (0.8-1.7) 1.17 (.27) Ն5 74 (18.3) 75 (12.2) 1.7 (1.0-3.0) 1.5 (0.9-2.4) Duration of drinking habits, y Ͻ5 47 61 1.4 (0.9-2.1) 1.3 (0.8-2.1) 5-14 57 71 1.4 (0.9-2.2) 0.51 (.49) 1.2 (0.8-2.0) 0.46 (.49) Ն15 194 296 1.2 (0.9-1.6) 1.0 (0.7-1.4) *Unless otherwise indicated, data are given as number (percentage). †Mantel-Haenszel (M-H) estimates adjusted for age and sex. ‡Ex-smokers and ex-drinkers were excluded. §Multiple logistic regression (MLR) estimates, including terms for age, sex, marital status, occupation, family history of psoriasis in first-degree relatives, body mass index, and, in turns, smoking and alcohol consumption. ࿣Reference category. Table 3. Odds Ratios for Psoriasis in Stratification by Sex According to Smoking and Alcohol Consumption Men Women No. of Case Patients/Controls MLR OR (95% CI)* ␹2 for Trend (P)† No. of Case Patients/Controls MLR OR (95% CI)* ␹2 for Trend (P)† Never smoked 56/101 1‡ 98/217 1‡ Former smokers 57/49 2.0 (1.1-3.1) 18/34 1.2 (0.6-2.1) Smokers, cigarettes per day Յ15 50/71 1.3 (0.7-2.0) 2.22 (.10) 45/59 1.7 (1.0-2.7) 14.8 (Ͻ.001) Ͼ15 56/70 1.4 (0.9-2.2) 24/15 3.9 (1.9-7.9) Nondrinkers 27/52 1‡ 67/115 1‡ Former drinkers 6/10 0.9 (0.3-3.0) 6/11 0.6 (0.2-1.9) Drinkers, drinks per day Յ2 93/138 1.2 (0.7-2.1) 4.6 (.03) 103/182 0.8 (0.5-1.2) 0.03 (.8) Ͼ2 93/91 1.9 (1.0-3.3) 9/17 0.7 (0.2-1.7) *Multiple logistic regression (MLR) estimates of odds ratio (OR) and 95% confidence interval (CI), including terms for age and, in turns, smoking and alcohol consumption. †Ex-smokers and ex-drinkers were excluded. ‡Reference category. ARCH DERMATOL/VOL 135, DEC 1999 WWW.ARCHDERMATOL.COM 1482 ©1999 American Medical Association. All rights reserved. on November 10, 2010www.archdermatol.comDownloaded from
  5. 5. cal manifestations. It is also difficult to standardize the as- sessment of the onset of the different skin disorders pre- sentedbythecontrolgroup.Wewerenotinterestedinacute exposures as triggers of the disease, but in more chronic, predisposing factors. As a consequence, precise onset defi- nition is not such a crucial problem in our analyses. The retrospective nature of our study is a more gen- eral limitation, with its potential for recall and informa- tion bias. It was reassuring that the frequency of smok- ing and alcohol consumption in our control group was similar to the estimates reported for the Italian popula- tion during the same period.23 It was also reassuring that for another exposure frequently reported as a risk factor in humans, namely coffee consumption, no association was documented. The statistical power of our subgroup analyses may be questioned. This issue is complicated by multiple sta- tistical testing. Since we did not make any correction for multiple tests, we advise readers to give more weight to our overall results than to any specific result in sub- groups, which should be taken as mainly explorative. In Italy, women tend to have a remarkably low alcohol con- sumption,24 and in our study, only 9 female case patients (4.8%) reported consuming more than 2 drinks per day. As a consequence, the analysis for high alcohol consump- tion lacks substantial statistical power. Recent Italian fig- ures indicate that greater proportions of men than women have given up smoking. The association between previ- ous smoker status and psoriasis in men suggests that, com- pared with the controls, a greater proportion of male pa- tients with psoriasis gave up smoking, perhaps because of early symptoms of the disease. If selective quitting is im- plicated, then the risk for current smoker status among men may be underestimated by our study. The associations we have documented may, in prin- ciple, represent the effect of an underlying, unmeasured confounding factor such as psychological stress.25 We did not assess stressful life events. Type A personality and psychological stress have been correlated with smoking and heavy alcohol consumption.26 However, the strong association between smoking and pustular lesions, even if based on a limited number of cases, is more indicative of a genuine biological effect. More than 4000 substances have been identified in cigarette smoke. Many of the adverse effects of smoke may result from oxidative damage to critical biological sub- stances.27 Such damage could result from oxidants present in cigarette smoke, eg, carbon monoxide, and from the activation of phagocytic cells that generate reactive oxygen species. In 1 study, polymorphonuclear leuko- cytes from smokers with psoriasis responded to a sig- nificantly greater degree to a standard chemotaxin than did polymorphonuclear leukocytes from nonsmokers with psoriasis, control smokers, and control nonsmokers.28 High levels of arachidonic acid metabolites have been documented in psoriatic lesions.29 Peroxidation of ara- chidonic acid by smoke may lead to the formation of F2- isoprostanes. Concentrations of these substances are in- creased dramatically in animal models of oxidant injury and increased in smokers.27 Recently, nicotinic cholin- ergic receptors have been demonstrated on keratino- cytes stimulating calcium influx and accelerating cell dif- ferentiation.30 Constant stimulation of these receptors may control keratinocyte adhesion and upward migration in the epidermis. Smoking and nicotine seem to influence inflammatory processes in the skin.31,32 The increased risk for psoriasis in women who are smokers, together with the higher prevalence of psoriasis among men compared with women documented in sev- eral population studies,33 points to the possible role of hor- monal and reproductive factors, since smoking has a well- defined antiestrogenic effect.34 Heavy alcohol consumption in men may increase the risk for infection or mechanical trauma that, in turn, may affect psoriasis. Moreover, an effect of alcohol on lymphocyte transformation has been suggested.35 If smoking and, possibly limited to men, al- Table 4. Odds Ratio for Selected Clinical Varieties of Psoriasis According to Smoking and Alcohol Consumption Ordinary Plaque* Mainly Flexural Pustular No. of Case Patients MLR OR (95% CI)† ␹2 for Trend (P)‡ No. of Case Patients MLR OR (95% CI)† ␹2 for Trend (P)‡ No. of Case Patients MLR OR (95% CI)† ␹2 for Trend (P)‡ Never smoked 141 1§ 7 1§ 6 1§ Former smokers 67 1.5 (1.0-2.3) 4 2.2 (0.6-8.1) 4 3.7 (0.9-13.7) Smokers, cigarettes per day Յ15 78 1.3 (0.9-1.8) 6.6 (.01) 7 2.4 (0.8-7.4) 0.7 (.40) 10 5.4 (1.9-15.5) 12.6 (Ͻ.001) Ͼ15 68 1.7 (1.1-2.5) 3 1.6 (0.4-7.0) 9 10.5 (3.3-33.5) Nondrinkers 83 1§ 3 1§ 8 1§ Former drinkers 9 0.7 (0.3-1.8) 1 2.4 (0.2-25) 2 1.2 (0.7-7.0) Drinkers, drinks per day Յ2 169 1.0 (0.7-1.4) 1.2 (.20) 12 1.9 (0.5-7.2) 1.4 (.20) 15 0.8 (0.3-2.0) 0.1 (.75) Ͼ2 93 1.5 (0.9-2.4) 5 2.7 (0.5-13) 4 0.5 (0.1-2.2) *This category includes 30 cases of chronic plaque psoriasis associated with a guttate flare. †Multiple logistic regression (MLR) estimates of odds ratio (OR) and 95% confidence interval (CI), including terms for age, sex, and, in turns, smoking and alcohol consumption. ‡Ex-smokers and ex-drinkers were excluded. §Reference category. 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  6. 6. cohol consumption cause psoriasis, the impact on public health would be far from negligible. The population- attributable fraction for smoking calculated from our study was about 0.2, indicating that about 1 in 5 cases of pso- riasis may be related to smoking. Independent of their causal role, the associations we have documented could improve our understanding of the comorbidity related to psoriasis and should be taken into consideration when pro- viding care for the disease. In addition, our data concern- ing pustular psoriasis suggest that chronic exposure to se- lected environmental factors may influence the clinical expression of psoriasis. The effect of environmental fac- tors on the extension, distribution (eg, acral lesions), clini- cal variety, and response to treatment of psoriasis should be evaluated further in prospective studies. Accepted for publication June 24, 1999. The study was partly supported by the following phar- maceuticalcompanies:Janssen-Cilag,ColognoMonzese;Roche, Milano; Schering, Segrate; Boehringer Ingelheim, Firenze; Glaxo-Wellcome, Verona; and Novartis, Origgio, Italy. We wish to thank Gillian Jarvis for her editorial as- sistance and the dermatologists from the participating cen- ters for making this study possible. Reprints: Luigi Naldi, Clinica Dermatologica, Os- pedali Riuniti, L go Barozzi 1, 24100 Bergamo, Italy (e- mail: REFERENCES 1. Kavli G, Førde OH, Arnesen E, Stenvold SE. Psoriasis: familial predisposition and environmental factors. BMJ. 1985;291:999-1000. 2. Chaput JC, Poynard T, Naveau S, Penso D, Durrmeyer O, Suplisson D. Psoria- sis, alcohol, and liver disease. BMJ. 1985;291:25. 3. Braathen LR, Botten G, Bjerkedal T. Psoriasis in Norway: a questionnaire study of health status, contact with paramedical professions and alcohol and tobacco consumption. Acta Derm Venereol. 1989;142(suppl):9-12. 4. 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Participants From the Psoriasis Study Group of the Italian Group for Epidemiologic Research in Dermatology Steering Committee T. Cainelli, MD; A. Rebora, MD; A. Peserico, MD; G. Tognoni, MD. Regional Coordinators Catania Clinica Universita`, Catania: A. Di Prima, MD. Padova Clinica Universita`, Padua: A. Belloni Fortina, MD; A. Peserico, MD. Napoli Clinica I Universita`, Naples: N. Balato, MD. Ferrara Clinica Universita`, Ferrara: A. R. Virgili, MD. Terni Clinica Universita`, Terni: P. L. Bruni, MD. Ospedale Militare, Taranto: V. Ingordo, MD. Arcispedale S. Maria Nuova, Reggio Emilia: G. Lo Scocco, MD. Torino Clinica Universita`, Turin: C. Solaroli, MD; P. Puiatti, MD. Verona Clinica Universita`, Verona: D. Schena, MD; A. Barba, MD; C. Chieregato, MD. Ospedale Riuniti, Bergamo: A. Di Landro, MD. Ospedale Civile, Cremona: E. Pezza- rossa, MD. Bologna Clinica Universita`, Bologna: S. Marzaduri, MD. Ospedale M. Bufalini, Cesena: R. Morelli, MD. Milano Clinica Universita`, Ospedale S. Paolo, Milan: R. Vergani, MD; C. Pazzini, MD. Firenze Clinica Universita`, Florence: P. Carli, MD; W. Volpi, MD. Spedali Civili, Brescia: P. G. Calzavara-Pinton, MD. Napoli Clinica II Universita`, Naples: F. Grimaldi-Filioli, MD; A. Lo Schiavo, MD. Casa Sollievo della Sofferenza, S. Giovanni Rotondo: M. Iannantuono, MD. Ospedale S. Paolo, Savona: A. Farris, MD; C. Micalizzi, MD. Ospedale Nuovo, Monza: E. Rossi, MD. ARCH DERMATOL/VOL 135, DEC 1999 WWW.ARCHDERMATOL.COM 1484 ©1999 American Medical Association. All rights reserved. on November 10, 2010www.archdermatol.comDownloaded from