Prevalence, Correlates and Characteristics of Chronic Pruritus: A Population-based Cross-sectional Study

Transcription

1 Act Derm Venereol 2011; 91: INVESTIGATIVE REPORT Prevlence, Correltes nd Chrcteristics of Chronic Pruritus: A Popultion-bsed Cross-sectionl Study Uwe Mtterne 1, Christin J. Apfelbcher 1, Adrin Loerbroks 2, Tmr Schwrzer 1, Mrion Büttner 1, Robert Ofenloch 1, Thoms L. Diepgen 1 nd Elke Weisshr 1 1 Deprtment of Clinicl Socil Medicine, Occuptionl nd Environmentl Dermtology, University Hospitl Heidelberg, University of Heidelberg, Germny, 2 Mnnheim Institute of Public Helth, Socil nd Preventive Medicine, Medicl Fculty Mnnheim, University of Heidelberg, Germny Pruritus is the most frequent symptom in dermtology. Its impct on qulity of life is substntil. Epidemiologicl dt on chronic pruritus (> 6 weeks) t the popultion level is sprse, but is importnt in order to understnd the burden nd risk fctors of this distressing symptom. The im of this popultion-bsed cross-sectionl study ws to estimte the point, 12-month nd lifetime prevlence of chronic pruritus, ssessing its ssocition with sociodemogrphic vribles nd describing its chrcteristics. A vlidted postl questionnire ws sent to 4,500 individuls in from the Germn generl popultion. Three contct ttempts were mde. The response rte ws 57.8% (n = 2,540). The point prevlence of chronic pruritus ws 13.5% (95% confidence intervl (95% CI) %), 12-month prevlence 16.4% ( %) nd lifetime prevlence 22.0% ( %). Multivrite nlyses found only ethnic origin independently ssocited with chronic pruritus. The impct of chronic pruritus on qulity of life nd emotionl well-being ppers to depend on severity rther thn on the presence of the symptom lone. This is the first study to investigte vrious prevlence estimtes of chronic pruritus t the popultion level. Despite its limittions (self-report nd potentil self-selection) this study indictes high burden of chronic pruritus in society. Key words: epidemiology; chronic pruritus; popultion; qulity of life; prevlence. (Accepted Mrch 16, 2011.) Act Derm Venereol 2011; 91: Uwe Mtterne, Clinicl Socil Medicine, Occuptionl nd Environmentl Dermtology, University Hospitl Heidelberg, Thibutstrsse 3, DE Heidelberg, Germny. E-mil: uwe.mtterne@med.uni-heidelberg.de Although there re dt on the occurrence of pruritus in ptient smples (6 10), epidemiologicl dt on the occurrence nd chrcteristics of chronic pruritus (defined s lsting for t lest 6 weeks (11)) t the popultion level do not exist (12, 13), but re importnt in order to understnd the burden of this distressing symptom. A focus on symptoms in dermto-epidemiology provides new contribution to the ssessment of the burden of skin morbidity in the community (13). Popultion-bsed studies, such s the Lmbeth study (14), hve shown prevlence of prurigo nd llied conditions of 8.2%, while Norwegin study (15, 16) reported prevlence of cute pruritus within the lst week of 8.4% in n urbn popultion ged yers. A popultion-bsed study in Frnce estimted the prevlence of pruritus t 12.4% during 2-yer period (17); however, no description ws provided of how chronic pruritus ws defined. Neither of these popultion-bsed studies ssessed chronic pruritus (point, 12-month, lifetime prevlence) or used well-defined criteri for the ssessment of chronic pruritus. To our knowledge there is only one study (n = 11,732) mesuring chronic itch in non-disesed popultion (18). However, only n estimte of the point prevlence of chronic pruritus (16.7%) ws given nd the popultion under study were employees seeking erly detection cncer screenings. To dte, no study hs scertined the point, 12-month nd lifetime prevlence of chronic pruritus (defined s lsting for t lest 6 weeks) t the popultion level t lrge. The present study, conducted by the Epidemiology of Chronic Pruritus Reserch Group (ECPRG) bsed t the University Hospitl Heidelberg, Germny, imed to determine prevlence estimtes of chronic pruritus in the generl popultion, to ssess its ssocition with sociodemogrphic vribles, nd to describe its chrcteristics. Pruritus is not only the most common symptom in dermtology; it is lso frequently encountered in vrious systemic, psychitric nd neurologicl conditions. It lso occurs s result of drug nd mediction intke (1, 2) nd is common side-effect in ptients on hemodilysis (3). Severl studies suggest high impct on qulity of life (4 6). Methods The study ws pproved by the ethics committee of the University of Heidelberg (S-120/2008). The study ws conducted in full ccordnce with the World Medicl Assocition s Declrtion of Helsinki. Results were reported in line with the Strengthening the Reporting of Observtionl Studies in Epidemiology (STROBE) recommendtions (19). The minimum smple size needed to detect prevlence of 10% with 95% confidence nd 2011 The Authors. doi: / Journl Compiltion 2011 Act Dermto-Venereologic. ISSN

2 Epidemiology of chronic pruritus in the generl popultion 675 2% precision is 864 (20). Expecting response rte of 60% would require 1,440 individuls in ech group. This estimte ws incresed to 1,500 per group. Hence, ddresses of 4,503 individuls ged > 18 yers were drwn rndomly from the Community registries in two cities (Heidelberg nd Ludwigshfen) nd six surrounding rurl communities in Southwest Germny. Registrtion with the locl uthorities is compulsory in Germny. A previously vlidted questionnire, developed for the ssessment of the prevlence nd chrcteristics of chronic pruritus in the generl popultion (21), ws sent by post. All non-responders received one postl reminder fter 2 months. Bsed on the results of pre-test (22), those who remined non-responders fter the first reminder were either contcted by telephone if their number ws listed in the telephone directory or received second postl reminder, including shortened version of the questionnire, if no telephone number could be obtined. Dt collection took plce between November 2008 nd July Dt ws entered twice by two independent persons nd ll observed rndom or potentilly systemtic inconsistencies between nd within resulting dt were solved to mximize dt qulity. The questionnire (21) ws structured into five sections. All prticipnts completed the first section on sociodemogrphic chrcteristics (sex, ge, occuptionl sttus, eduction nd ethnic origin) nd second section on the three prevlence (point, 12-month, lifetime) items. Only individuls who reported current chronic pruritus continued with the reminder of the questionnire, which contined nother three sections deling with the experience of current chronic pruritus tht lsted for t lest 6 weeks. The third section (chrcteristics of chronic pruritus) mesured the durtion, frequency of occurrence nd locliztion of chronic pruritus. Fourthly, visul nlogue scle, rnging from zero to ten ssessed the verge subjective severity of experienced chronic pruritus. The fifth section inquired bout pruritus-relted qulity of life (PrQoL) impirments nd the effect tht chronic pruritus hs on emotionl well-being. A finl question in this section ssessed whether helth sttus ws ffected by other conditions. Finlly, respondents were sked whether they were wre of the cuse of their chronic pruritus, whether tretment by physicin ws ongoing or hd previously occurred, nd whether this tretment hd resulted in llevition of the pruritus. Sttisticl nlyses were conducted using SPSS 19. Dt re described by bsolute nd reltive frequencies, or by mens nd stndrd devitions, respectively, nd 95% confidence intervls (CI) for these coefficients estimtes were computed. Comprisons between respondents, nd non-respondents nd those refusing to prticipte, were crried out by independent t-tests for the continuous vrible ge nd by χ 2 -test for the sex distribution. Correltions between pruritus severity, durtion, nd qulity of life (QoL) nd emotionl well-being re reported by Person s correltion coefficients. Associtions of chronic pruritus with sociodemogrphic vribles were evluted by binry logistic regression nlysis, djusting for confounding in multivrible nlysis. Results Response rte, drop-out nlyses nd smple description Tble I. Attrition nd drop-out nlyses Subjects n (%) Age, yers Men ± SD Sex, femle (%) Totl contcted 4,503 (100) 48.6 ± Excluded 105 (2.3) Decesed 14 (0.3) 78.2 ± Unknown ddress 83 (1.8) 50.4 ± Unble to prticipte 8 (0.2) 68.3 ± Totl included 4,398 (100) Agreed to prticipte (prticipnts) 2,540 (57.8) 51.7 b ± b Refused to prticipte 128 (2.9) 58.4 b ± Did not respond 1,730 (39.3) 43.2 b ± b Due to severe dementi or cognitive impirment. b Significntly different t p < SD: stndrd devition. Of the 4,503 individuls contcted, 105 individuls were excluded due to deth, n unknown ddress or their inbility to prticipte in the survey s result of severe dementi or cognitive impirment. Of the remining 4,398 individuls, 2,540 (57.8% response rte) greed to prticipte in the study, 128 (2.9%) refused to prticipte, nd 1,730 (39.3%) did not respond fter two reminders (Tbles I nd II). Prticipnts were significntly younger thn those who ctively refused prticiption nd significntly older thn those who did not respond t ll. The proportion of femles ws significntly higher mong prticipnts thn mong non-respondents (Tble I). Tble III provides the demogrphic chrcteristics of the smple. Slightly more women thn men responded to the survey. Hlf of the smple ws working, while pproximtely one-third ws retired. Prevlence of chronic pruritus within the totl smple (n = 2,540) nd s function of sociodemogrphic vribles (univrite nlyses) Of the totl smple, 13.5% reported current chronic pruritus, 16.4% reported chronic pruritus within the previous 12 months, nd 22.0% reported hving hd chronic pruritus t lest once in their lives (Tble IV). The lifetime prevlence of chronic pruritus decresed with ech contct wve (Tble II). Femles were more likely to suffer from current, 12-month nd lifetime pruritus (Tble SI (vilble t: 40/ ). However, only the difference with regrd to lifetime pruritus ws significnt. Age ws not significntly ssocited with chronic pruritus when the outcome ws current pruritus or pruritus within the lst 12 months. However, significnt ssocition of ge with lifetime pruritus ws observed. The trend ppered Tble II. Response rte by contct wve Contct wve Smple n Cumultive Response rte n (%) First postl 4, (22.0) 31.4 Second postl 4,467 1,453 (32.5) 29.5 Third (postl) 4,467 1,694 (37.9) 22.0 Third (telephone) 4,398 2,540 (57.8) 22.0 Lifetime prevlence of chronic pruritus (%) 4,503 minus those excluded (decesed, unknown ddress, unble to prticipte).

3 676 U. Mtterne et l. Tble III. Demogrphics of respondents (n = 2,540) Reltive frequency 95% CI Sex, % Femle Mle Age, men ± SD 51.7 ± Occuptionl sttus, % Working Retired Other Schooling, % Elementry Secondry (ordinry) Secondry (dvnced) Other Origin, % Germn Other Pternity leve, housewives, unemployed, students. SD: stndrd devition; 95% CI: 95% confidence intervl. to be non-liner, but in bimodl fshion with peks for ge groups nd yers, respectively. No significnt differences in prevlence estimtes emerged s function of occuptionl sttus, schooling or plce of residence. However, individuls with non-germn ethnic origin were significntly more likely to hve experienced current, 12-month nd lifetime pruritus (Tble SI). Assocition of chronic pruritus with sociodemogrphic vribles in multivrible nlyses (n=2,540) Three multivrible logistic regression nlyses, with current, 12-month nd lifetime pruritus s the dependent vribles, nd sex, ge, occuptionl sttus, schooling, ethnic origin nd plce of residence (urbn vs. rurl) s predictors, were conducted (Tble V). Only ethnic origin emerged s significnt correlte of current pruritus nd pruritus within the lst 12 months, while mrginlly significnt ssocition ws found with lifetime pruritus. Non-Germn ethnic origin incresed the odds of hving chronic pruritus in comprison with Germn origin. Chrcteristics of chronic pruritus nd impct on pruritusrelted qulity of life nd emotionl well-being (n = 343) All prticipnts who reported current chronic pruritus (n = 343) were sked to provide dditionl informtion on their pruritus. The chrcteristics of chronic pruritus re displyed in Tble VI. The men severity Tble IV. Prevlence of chronic pruritus for totl smple (n = 2,540) % (n) 95% CI Totl Point 13.5 (343) month 16.4 (413) Lifetime 22.0 (559) CI: confidence intervl. Tble V. Results from multivrible logistic regression with point, 12-month nd lifetime prevlence of chronic pruritus regressed on sociodemogrphic predictors (n = 2,540) mesured by visul nlogue scle (VAS) on scle from 0 to 10 ws 5.3 (SD = 2.13). PrQoL, mesured by four items on scle from 1 (no impct) to 4 (extreme impct) ws 1.7 (SD = 0.65), nd the effect of pruritus on emotionl well-being (four items, sme scle) ws 1.53 (SD=0.68). Chronic pruritus severity mesured by VAS ws significntly ssocited with impired PrQoL (r = 49, p < 0.001) nd emotionl well-being (r = 0.45, p < 0.001). The durtion of chronic pruritus hd mrginl effect on PrQoL (r = 0.11, p = 0.08), but no significnt effect on emotionl well-being. The chronic pruritus durtion ws significntly ssocited with chronic pruritus severity (r = 0.20, p = 0.001). The cuse of pruritus ws known by 50.5% of the respondents. The mjority ttributed chronic pruritus to skin conditions, some to psychosomtic nd few to systemic cuses. Fifty percent of respondents reported hving sought tretment for their chronic pruritus. Tretment ws lrgely perceived to llevite the symptom in 21%, while 48% reported t lest some llevition of the symptom with tretment. DISCUSSION Point OR (95% CI) 12-month OR (95% CI) Lifetime OR (95% CI) Sex Mle Femle 1.01 ( ) 1.12 ( ) 1.21 ( ) Age, yers 1.00 ( ) 1.00 ( ) 1.00 ( ) Occuptionl sttus Working Retired 1.27 ( ) 1.18 ( ) 1.08 ( ) Other 1.19 ( ) 1.04 ( ) 1.07 ( ) Schooling Elementry Secondry 0.97 ( ) 0.96 ( ) 1.05 ( ) ordinry Secondry 1.02 ( ) 1.09 ( ) 1.25 ( ) dvnced Other 0.57 ( ) 0.67 ( ) 0.81 ( ) Origin Germn Other 1.46 ( ) 1.56 ( ) 1.35 ( ) Plce of residence Urbn Rurl 0.91 ( ) 0.99 ( ) 1.05 ( ) OR: odds rtio; 95% CI: 95% confidence intervl. While there re some dt regrding the prevlence of chronic pruritus in specific conditions or popultions, no dt exist bout how common the symptom chronic pruritus is t the popultion level. Becuse pruritus is symptom ssocited with mny medicl conditions, nd becuse not everyone with chronic pruritus my present the symptom to physicin, the need for popultionbsed studies estimting the prevlence of the symptom

4 Epidemiology of chronic pruritus in the generl popultion 677 Tble VI. Chrcteristics of current chronic pruritus (n = 343) Reltive frequency (%) Durtion, months > > > > > > Pruritus during the dy Never 0.3 Rrely 4.3 Every now nd then 27.2 Occsionlly 32.9 Often 30.9 Alwys 4.3 Pruritus during the night Never 19.8 Rrely 20.5 Every now nd then 20.1 Occsionlly 16.4 Often 19.5 Alwys 3.7 Pruritus every dy 71.9 Locliztion of chronic pruritus Mostly in sme locliztions (loclized) 91.4 Mostly in different locliztions (generlized I) 25.9 Mostly whole body ffected (generlized II) 14.6 Antomicl locliztion Fce/neck 25.9 Bck 32.7 Chest/belly 20.4 Anogenitl 19.0 Sclp 44.6 Arms 28.6 Hnds 21.0 Legs 30.9 Feet 16.6 Multiple responses possible. becomes pprent. Compred with other lrge-scle studies mesuring prurigo nd llied conditions (14), cute pruritus within the lst week (15, 16), or undefined chronic pruritus within the pst 2 yers (17), the estimtes rrived t in this study re higher. Chronic pruritus requires pruritus to be present for minimum of 6 weeks (11), hence one could rgue tht the point, 12-month nd lifetime prevlence of chronic pruritus should be lower compred with, for instnce, cute pruritus within the lst week ssuming the study popultions re otherwise comprble. However, the present study used previously vlidted questionnire, lending support to the obtined results. In ddition, nother lrge-scle study (18) investigting 11,732 employees, prticipting in skin cncer screening reported point prevlence of chronic pruritus (> 6 weeks) of 16.7%; result tht exceeds even the point prevlence estimte obtined in this study. We lso found the prevlence of chronic pruritus to decrese with ech contct wve. Assuming the most extreme scenrio of no single dditionl cse to be detected if 100% response rte ws chieved, lifetime prevlence of 12.6% (556/4,398) would still result. Although univrite nlyses reveled prevlence estimtes to be higher for femles, significnt sex difference ws found only for lifetime chronic pruritus. This result confirms previous reserch in cute pruritus (15) nd chronic pruritus (23), while multivrible regression filed to find n ssocition with sex in the present study. Similrly, lthough some reserch indictes tht the prevlence of chronic pruritus increses with ge (18, 24), the present study did not find such n ssocition in multivrible nlysis. Dlgrd et l. (15) found cler liner decrese in non-chronic pruritus with incresing ge, while the present study found bimodl distribution of current, 12-month nd lifetime pruritus s function of ge. More reserch is needed in order to fully estblish how pruritus is relted to ge. Multivrible logistic regression nlyses reveled only ethnic origin to be significnt correlte of chronic pruritus. The mjority of the respondents of non-germn ethnic origin were of Turkish orgin. Whether the prevlence of chronic pruritus vries cross ethnicities, perhps due to vrying risk fctors or differing socio-culturl constructs of the symptom or vrying norms, remin open questions tht future studies need to ddress. Differentil reporting of the symptom my lso hve occurred. Dlgrd et l. (16), using univrite nlyses, found the prevlence of pruritus within the lst week (rther thn chronic pruritus) to differ mong ethnic groups. How ever, these differences were confined to men only. The present study found no significnt differences in prevlence estimtes s function of urbn vs. rurl residence. Direct comprisons with other studies re not possible, since the effect of residentil ctegory ws not ddressed previously. Dlgrd et l. (15, 16) nd Re et l. (14) studied urbn smples. Anlyses strtified by living re were not reported by Wolkenstein et l. (17). Almost hlf of the respondents with current chronic pruritus reported hving hd chronic pruritus for more thn 3 yers, with lmost one-third hving hd the symptom for more thn 8 yers. Twenty-five percent of the study prticipnts with pruritus (n = 597) hd hd chronic pruritus for t lest 5 yers (18). These findings suggest tht chronic pruritus is often highly pervsive nd long-lsting symptom. More respondents reported pruritus during the dy thn during the night, which is in greement with previous reserch (23). Nevertheless, mong the PrQoL impirment questions there were lso considerble number of respondents who reported pruritus during the night s well s sleep disruption. Although 91% hd loclized pruritus, 25% reported hving pruritus tht ffected different locliztions (Tble VI: generlized I). As multiple responses were possible, it ppers tht there re individuls who encounter both loclized pruritus s well s pruritus tht ffects different loctions. Previous reserch in disesed popu-

5 678 U. Mtterne et l. ltions distinguishing between generlized nd loclized pruritus in mutully exclusive mnner found 26% to be loclized nd 74% to be generlized pruritus (12). The present study lso reveled pproxi mtely 15% to hve pruritus tht ffects the whole body, result which is similr to the 16% reported by Ständer et l. (18). Although ssocitions between pruritus nd QoL hve been shown consistently (17, 21, 25), in the present study the impct of chronic pruritus on PrQoL ws moderte on verge, suggesting tht individuls could come to terms with the symptom. However, significnt correltion between VAS, on the one hnd, nd PrQoL nd emotionl well-being, on the other hnd, indictes tht it is not pruritus per se, but the severity with which it is encountered tht impirs PrQoL nd reduces emotionl well-being. Chronic but mild pruritus my not hve such profound effects on PrQoL. Similr effects were reported by Holm et l. (26) in ptients with topic dermtitis. Although 51% of the smple with current chronic pruritus reported knowing the cuse of their pruritus, n lmost equl proportion did not. These individuls my not hve ttended physicin, or the cuse my not yet hve been determined. The ltter my be indictive of pruritus of unknown origin. In substntil proportion (8 44.5%) of individuls with chronic pruritus (12, 23) the cuses cnnot be estblished. Of the 50% who hd sought tretment for their chronic pruritic condition, pproximtely 70% observed llevition of the symptom. However, most reported only prtil llevition s result of tretment. Ptients with chronic pruritus often endure long nd complicted disese course, filure of therpy nd considerble reduction in qulity of life (27). The present dt bcks this observtion. A number of limittions of this study must be discussed. Firstly, lrger smple size would hve led to higher precision, s the confidence in the obtined estimtes would hve incresed. However, the necessry smple size ws bsed on power nlysis prior to dt collection. Secondly, dt ws obtined by self-report, which is subject to vriety of bises, most notbly socil desirbility nd recll bis. Pruritus is subjective experience (28); thus it is usully ssessed vi self-report nd this study is no exception. With regrd to self-selection, drop-out nlyses reveled respondents to be significntly older thn non-respondents nd prepondernce of femles in the smple. However, in multivrite nlyses sex, ge, occuptionl sttus, eduction or plce of residence were unrelted to chronic pruritus. Potentil selective prticiption ccording to these socio-demogrphic vribles is unlikely to hve bised our prevlence estimtes. Conclusion This is the first study to investigte the point, 12-month nd lifetime prevlence of chronic pruritus in the generl popultion. The results suggest tht the burden of chronic pruritus in the generl popultion is substntilly higher thn previously believed. Despite the reported limittions of this study, nd bering in mind the lck of popultion-bsed studies, this study ppers to offer the best estimte presently vilble. The results indicte high burden of the symptom of chronic pruritus in the generl popultion. Further reserch is needed to confirm the results of the present study. In ddition, s there is no dt on the incidence of chronic pruritus nd the fctors tht predispose individuls to develop chronic pruritus, this lso requires further reserch. Acknowledgments This study would not hve been possible without finncil support from the foundtion Friends of itch reserch in Germny (Förderverein Juckreizforschung e.v.). The uthors declre no conflicts of interest. References 1. Bigby M, Jick S, Jick H, Arndt K. Drug-induced cutneous rections. A report from the Boston Collbortive Drug Surveillnce Progrm on 15,438 consecutive inptients, 1975 to JAMA 1986; 256: deshzo RD, Kemp SF. Allergic rections to drugs nd biologic gents. JAMA 1997; 278: Mettng T, Puli-Mgnus C, Alscher DM. Uremic pruritus new perspectives nd insights from recent trils. Nephrol Dil Trnsplnt 2002; 17: Mthur VS, Lindberg J, Germin M, Block G, Tumlin J, Smith M, et l. A longitudinl study of uremic pruritus in hemodilysis ptients. Clin J Am Soc Nephrol 2010; 5: Elmn S, Hynn LS, Gbriel V, Myo MJ. The 5-D itch scle: new mesure of pruritus. Br J Dermtol 2010; 162: Wikstrom B. Itchy skin clinicl problem for hemodilysis ptients. Nephrol Dil Trnsplnt 2007; 22 Suppl 5: v3 v7. 7. Kntor GR, Lookingbill DP. Generlized pruritus nd systemic disese. J Am Acd Dermtol 1983; 9: Weisshr E, Kucenic MJ, Fleischer AB, Jr. Pruritus: review. Act Derm Venereol 2003; Suppl 213: Pisoni RL, Wikstrom B, Elder SJ, Akizw T, Asno Y, Keen ML, et l. Pruritus in hemodilysis ptients: interntionl results from the Dilysis Outcomes nd Prctice Ptterns Study (DOPPS). Nephrol Dil Trnsplnt 2006; 21: Yosipovitch G, Ansri N, Goon A, Chn YH, Goh CL. Clinicl chrcteristics of pruritus in chronic idiopthic urticri. Br J Dermtol 2002; 147: Ständer S, Weisshr E, Mettng T, Szepietowski JC, Crstens E, Ikom A, et l. Clinicl clssifiction of itch: position pper of the Interntionl Forum for the Study of Itch. Act Derm Venereol 2007; 87: Sommer F, Hensen P, Böckenholt B, Metze D, Luger TA, Ständer S. Underlying diseses nd, co-fctors in ptients with severe chronic pruritus: 3-yer retrospective study. Act Derm Venereol 2007; 87: Weisshr E, Dlgrd F. Epidemiology of itch: dding to

6 Epidemiology of chronic pruritus in the generl popultion 679 the burden of skin morbidity. Act Derm Venereol 2009; 89: Re JN, Newhouse ML, Hlil T. Skin disese in Lmbeth. A community study of prevlence nd use of medicl cre. Br J Prev Soc Med 1976; 30: Dlgrd F, Svensson A, Holm JO, Sundby J. Self-reported skin morbidity in Oslo. Associtions with sociodemo grphic fctors mong dults in cross-sectionl study. Br J Dermtol 2004; 151: Dlgrd F, Holm JO, Svensson A, Kumr B, Sundby J. Self reported skin morbidity nd ethnicity: popultionbsed study in Western community. BMC Dermtology 2007; 7: Wolkenstein P, Grob JJ, Bstuji-Grin S, Ruszczynski S, Roujeu JC, Revuz J. French people nd skin diseses: results of survey using representtive smple. Arch Dermtol 2003; 139: Ständer S, Schäfer I, Phn NQ, Blome C, Herberger K, Heigel H, et l. Prevlence of chronic pruritus in Germny: results of cross-sectionl study in smple working popultion of 11,730. Dermtology 2010; 221: von Elm E, Altmn DG, Egger M, Pocock SJ, Gotzsche PC, Vndenbroucke JP, et l. The Strengthening the Reporting of Observtionl Studies in Epidemiology (STROBE) Sttement: Guidelines for Reporting Observtionl Studies. Epidemiology 2007; 18: Lemeshow S, Hosmer DW, Klr J, Lwng SK. Adequcy of smple size in helth studies. Chichester, UK: John Wiley & Sons, Mtterne U, Strssner T, Apfelbcher CJ, Diepgen TL, Weisshr E. Mesuring the prevlence of chronic itch in the generl popultion: development nd vlidtion of questionnire for use in lrge-scle studies. Act Derm Venereol 2009; 89: Apfelbcher CJ, Loerbroks A, Mtterne U, Strssner T, Büttner M, Weisshr E. Informed consent ffects prevlence estimtes in n epidemiologicl study on chronic pruritus: lessons lerned from pretest. Ann Epidemiol 2009; 19: Weisshr E, Apfelbcher C, Jger G, Zimmermnn E, Bruckner T, Diepgen TL, et l. Pruritus s leding symptom: clinicl chrcteristics nd qulity of life in Germn nd Ugndn ptients. Br J Dermtol 2006; 155: Lio YH, Chen KH, Tseng MP, Sun CC. Pttern of skin diseses in geritric ptient group in Tiwn: 7-yer survey from the outptient clinic of university medicl center. Dermtology 2001; 203: Desi NS, Poindexter GB, Monthrope YM, Bendeck SE, Swerlick RA, Chen SC. A pilot qulity-of-life instrument for pruritus. J Am Acd Dermtol 2008; 59: Holm EA, Wulf HC, Stegmnn H, Jemec GB. Life qulity ssessment mong ptients with topic eczem. Br J Dermtol 2006; 154: Bthe A, Mtterne U, Dewld M, Grnde T, Weisshr E. Eductionl multidisciplinry trining progrmme for ptients with chronic pruritus. Act Derm Venereol 2009; 89: Dlgrd F, Lien L, Dlen I. Itch in the community: ssocitions with psychosocil fctors mong dults. J Eur Acd Dermtol Venereol 2007; 21: