Epidemiology of Moderate-to-Severe Plaque Psoriasis in a Canadian Surveyed Population

JMS_2010_09066 167..174Epidemiology of Moderate-to-Severe Plaque Psoriasis in a Canadian Surveyed Population Kim Papp, Fernando Valenzuela, Yves Poulin, Geula Bernstein, and Norman Wasel
Background: Limited data are available on the epidemiologic features of psoriasis in Canada.
Objective: To investigate the epidemiologic features and burden of moderate-to-severe psoriasis in a Canadian population.
Methods: An online survey was conducted using a consumer panel. Eligible respondents indicated a diagnosis of psoriasis and
plaque-type psoriasis of at least moderate severity. Eligibility was validated according to self-reported body surface area (BSA)
involvement, sensitive areas affected, and/or current treatment.
Results: Of the 514 respondents who completed the survey, 62% estimated a BSA involvement of $ 3% within the past 5 years.
Onset of psoriasis occurred earlier in females than in males. Nail involvement was more commonly reported in individuals with
psoriatic arthritis compared to those without. Several symptoms were more likely described as ‘‘constantly’’ or ‘‘near constantly’’
experienced by females than by males. Comorbidities commonly reported were hypertension, dyslipidemia, and overweight or obesity.
Conclusions: The findings are consistent with a substantial burden attributed to moderate-to-severe plaque psoriasis in a
Canadian population.
Objectif: Explorer les caracteristiques epidemiologiques et le fardeau du psoriasis modere a grave chez une population du
Canada.
Methodes: Une enquete en ligne a ete effectuee aupres d’un groupe-temoin de consommateurs. Les repondants admissibles ont
recu un diagnostic de psoriasis et de psoriasis en plaque de gravite moyenne ou plus. L’admissibilite a ete validee selon une auto-
evaluation de la surface corporelle, les zones sensibles affectees, ou le traitement actuellement suivi.
Resultats: L’enquete a ete remplie par 514 repondants. Parmi ces personnes, 62 % ont estime que leur surface corporelle affectee
au cours des 5 dernieres annees etait egale ou superieure a 3 %. Le declenchement du psoriasis a eu lieu chez les hommes plus
tardivement que chez les femmes. L’atteinte ungueale etait plus frequente chez les personnes souffrant de polyarthrite psoriasique.
Plusieurs symptomes ont ete decrits comme ayant lieu constamment ou presque constamment chez les femmes que chez les
hommes. Les comorbidites les plus souvent mentionnees sont l’hypertension, la dyslipidemie, et l’exces de poids ou obesite.
Conclusions: Les resultats de l’enquete correspondent a un fardeau considerable attribue au psoriasis en plaque modere a grave
chez la population canadienne.
with an unpredictable clinical course and variable
morphology, distribution, and severity.1 Plaque-type psor-
iasis, the most common form,1 is associated with substantial
physical and psychosocial impairment and comorbidities
that contribute to the burden of disease.2–4 Psoriasis is
estimated to affect 0 to 4.8% of individuals worldwide,5–26
with the highest prevalence (11.8%) reported for Kazach’ye,
in the Arctic region of Russia.11 Estimates for Canada
generally range from 1 to 3%5,6 and from 2.2 to 2.6% in
randomly selected US populations,7–9 although occurrences
as high as 4.7% and 4.6% have been reported for Canada
and the United States, respectively.11 Variable estimates
within the same region may be due to the method of
assessment (eg, clinical versus population based or evidence
From the K. Papp Clinical Research, Probity Medical Research, Waterloo,
ON; Department of Dermatology, University of Chile, Santiago, Chile;
Department of Medicine, Universite Laval, Hopital Hotel-Dieu de
Quebec and Centre Dermatologique du Quebec Metropolitain, Quebec,
QC; AXON Communications, Toronto, ON; Stratica Medical and
Department of Medicine, University of Alberta, Edmonton, AB.
Presented in part as an oral presentation at the Canadian Dermatology
Association 83rd Annual Conference, Montreal, QC (June 22–July 2,
2008), and in poster format at the 17th Congress of European Academy
of Dermatology and Venereology, Paris, France (September 17–21,
2008).
Address reprint requests to: Kim Papp MD, K. Papp Clinical Research,
Probity Medical Research, 135 Union Street East, Waterloo, ON N2J
1C4; e-mail: [email protected].
# 2010 Canadian Dermatology Association
Journal of Cutaneous Medicine and Surgery, Vol 14, No 4 (July/August), 2010: pp 167–174 167
gathered through clinical examination versus survey ques-
tionnaire).27,28 Variability in estimates of prevalence
between regions worldwide may be attributed to differences
in ethnic or racial composition, genetics, or possibly
environmental and climate conditions.1,29,30
of moderate-to-severe psoriasis in a Canadian population.
Characterizing the local epidemiology of disease is impor-
tant for furthering understanding of its natural course in
that population, as well as the regional burden of illness
and associated comorbidities. The current study aimed to
define the epidemiology of plaque psoriasis in a Canadian
population of individuals self-reporting moderate-
to-severe disease. The findings from the study provide
insight into patient management in local practices and
highlight the substantial burden of disease.
Methods
A reliable population-wide, cross-sectional sample, repre-
sentative of the adult Canadian population (balanced by
region and gender), was achieved through use of
proprietary databases owned by Ipsos Canada and ICom
TargetSource.31 Between the two databases, a total sample
population of 3,845 prescreened, self-defined Canadian
adults ($ 18 years) with self-reported psoriasis received an
e-mail invitation to participate in the survey.{ A total of
1,671 of these individuals clicked the survey link (n 5 300
incompletes); of the 1,371 prescreened individuals, 857
were screened out. Reasons for screening out included not
diagnosed with psoriasis (n 5 449); not identified as
having plaque-type psoriasis (n 5 261); self-reported as
very mild or mild psoriasis, currently and at its worst in
the last 5 years (n 5 67); and body surface area (BSA)
involved , 3% and not affected on at least one sensitive
area and not currently taking prescribed oral or injectable
medication or photo- or light therapy (n 5 80). The target
sample size was 400 individuals with moderate-to-severe
plaque psoriasis. In total, 514 qualified respondents
completed the survey (n 5 347 female, n 5 167 male).
Survey Methodology
French) were approved by Research Review Board Inc. on
November 29, 2007. The online survey was designed to take
<30 minutes to complete and was conducted in December
2007. Responses to a screening questionnaire determined
eligibility for the study. Eligible subjects reported a diagnosis
of psoriasis by a physician, at least moderate severity of
disease currently or at some time in the past 5 years, and
plaque-type psoriasis through recognition of visual images
and description of plaques. In addition, eligible subjects met
at least one of the following criteria: a minimum self-
estimated BSA involvement of 3% at some time in the past 5
years using the palm method (ie, palm of the hand 5 <1%
BSA)9 or psoriasis on a sensitive area of the body (hands,
feet, scalp, face, or genitals),32,33 or current treatment with
prescription oral and/or injectable medication or photo- or
light therapy for psoriasis.
The study began with an assessment of quality of life
through two previously validated patient reported out-
come instruments, the generic SF-8 and the skin-specific
Dermatology Life Quality Index (DLQI),34,35 and then
followed with a broad range of subjective health-related
questions.
question. Percentages represent the weighted responses,
with N representing the number of people who were asked
the question. Correlation between associated variables was
calculated using the Pearson correlation coefficient, and p
values for data based on analysis of variance and the x2 test
were used to compare variables. To determine differences
with respect to age, data were analyzed according to the
following age categories: 18 to 34, 35 to 55, and $ 55 years.
Statistical significance levels were set at p , .05. No
correction was applied for multiple tests.
Results
database, 3,100 indicated that they have psoriasis, with
449 of these individuals later screened out for reporting
that they did not have a diagnosis from a physician. This
provides an estimated range for Canadian prevalence of 1.0
to 3.1% that incorporates the assumption that as many as
449 of 1,371 (33%) individuals may be self-diagnosed.
Eligible respondents were mainly female, and responses
were weighted 1:1 according to gender. The mean age of
respondents overall was 49.7 years (Table 1, Figure 1). An
{Survey data were retrospectively analyzed, with emphasis placed on
the reporting of epidemiologic features and burden of disease.
168 Papp et al
earlier mean age at onset of symptoms was reported by
female respondents (25.6 years) compared to males (30.0
years) (p 5 .0014; Table 2).
The majority of respondents (62%) self-reported
moderate-to-severe disease with a BSA involvement of $
3% at least once during the past 5 years (see Table 1). Self-
reported BSA involvement $ 3% was more commonly
reported in males (66%) than in females (58%) (x2,
p 5 .0377). Male and female respondents reported a
similar prevalence of psoriasis affecting the nail (44% and
37%, for males and females, respectively) (p 5 .1334);
psoriatic arthritis (PsA) (22% and 24%, for males and
females, respectively) (x2, p 5 .6477); and psoriasis
localized to the scalp, hands, or face (x2, p 5 .2575,
.8535, .9957, respectively) (Table 3). Males more com-
monly indicated plaque localization to the elbows
(p 5 .0046), legs (p 5 .0005), knees (p , .0001), back
(p , .0001), feet (p 5 .0341), genitals (p , .0001), and
‘‘other areas’’ (p 5 .0497) than females (based on x2, see
Table 3). Psoriasis of the nail was reported by respondents
within the age ranges of 18 to 34, 35 to 54, and $ 55 years
at a prevalence of 26%, 43%, and 44%, respectively, with
PsA found in 16%, 25%, or 24%, of respondents,
respectively. Nail involvement was more commonly
reported in individuals with PsA (66.4%) compared to
those without (32.7%; x2, p , .0001).
Symptoms reported as ‘‘constantly’’ or ‘‘near constantly’’
experienced by over half of patients were scaling (69%), skin
redness (61%), and itchiness or sensation of burning (51%;
Table 4). Females were more likely to report ‘‘constant’’ or
‘‘near constant’’ itchiness or sensation of burning (p 5 .0004),
bleeding (p 5 .0160), swollen fingers or toes (p 5 .009),
discomfort in joints or tendons (p 5 .0007), or morning
stiffness in joints (p 5 .0013, based on x2). Reports of
‘‘constant’’ or ‘‘near constant’’ redness and pain of the eye
were similar for both genders (x2, p 5 .0597; see Table 4).
Within the different age categories, there was a significant
impact on the likelihood to report ‘‘constant’’ or ‘‘near
constant’’ morning joint stiffness (x2, p 5 .0018), discomfort
in joints or tendons (x2, p 5 .0320), and itchiness or burning
(x2, p 5 .0217) (see Table 4).
Figure 1. Age distribution of survey respondents (N 5 514).
Table 1. Sociodemographic and Disease Characteristics of Survey
Respondents Who Satisfied Entrance Criteria for Study
Demographics of Respondents
Gender (% female) 51
Very mild/mild severity of psoriasis (current) 68,450 6 3,269
Moderate or more severe psoriasis (current) 59,550 6 2,387
Married/common law (%) 69
College education 49
University education 25
Psoriasis severity, current (%)
Very mild 12
Moderate 36
Severe 36
Affected BSA at worst in past 5 yr (%)
0–2% 38
3–9% 38
BSA 5 body surface area.
Table 2. Age at Onset of Symptoms of Psoriasis Reported by Male
and Female Survey Respondents (N 5 514)
Age, yr (%)
Gender 1–10 11–17 18–24 25–34 35–44 45–54 55–64 $ 65
Male 8 16 16 24 15 11 8 2
Female 14 23 16 17 15 8 5 0
Epidemiology of Plaque Psoriasis in a Canadian Population 169
Diagnosis of high blood pressure, dyslipidemia, and
obesity or overweight was reported by at least one-quarter
of male respondents (35%, 32%, and 25%, respectively), as
was obesity or overweight by females (39%) (Table 5). A
greater prevalence of comorbidities was generally reported
in the older age ranges, with the exception of depression
and anxiety. In the 18- to 34-year age range, the most
common comorbidities were obesity or overweight,
anxiety, and depression. Obesity or overweight, depres-
sion, and anxiety were also commonly reported by middle-
aged individuals (35–54 years), as well as high blood
pressure and dyslipidemia, compared to other comorbid-
ities. In respondents aged $ 55 years, high blood pressure
and dyslipidemia were reported by over half of individuals,
with obesity or overweight and diabetes also commonly
reported relative to the other chronic conditions.
The overall mean SF-8 Physical Component Score
(PCS; mean 46.0; 95% CI 45.0–47.0) and Mental
Component Score (MCS; mean 46.4; 95% CI 45.4–47.4)
represented clinically meaningful reductions from the
general population norm ($ 3 units from the 1998 US
population norm of 50).36–38 The results of the DLQI
demonstrated that psoriasis exerts at least a moderate
effect (ie, score $ 6) on the lives of 39% of respondents
and a very or extremely large effect (ie, score $ 11) on
15% of individuals. When provided with a number of
possible ‘‘feelings’’ associated with psoriasis (both negative
and positive), a higher proportion of females than males
reported self-consciousness (60% and 71%, respectively;
p 5 .0087), whereas the reporting of embarrassment (54%
and 59%, respectively) and inconvenience (57% and 63%,
respectively) was similar irrespective of gender (p 5 .2040
Table 3. Body Regions Affected in Survey Respondents Who Satisfied Entrance Criteria for Study
Body Region Total (N 5 514) (%) Male (%) Female (%)
x2 Test (p value for
difference between genders)*
Percentages are based on weighted data.
*p values do not include correction for multiple comparisons.
Table 4. Proportion of Respondents Constantly or Near Constantly Affected by Symptoms (N 5 514)
Symptom (%)
Scaling
Skin
redness
Itchiness/
Total 69 61 51 13 21 18 35 35 9
Gender
Male 68 63 43 10 23 13 28 28 6
Female 70 59 59 17 19 24 42 42 11
Age range (yr)
18–34 68 57 51 20 14 17 25 18 7
35–54 73 66 57 13 22 18 40 38 9
$ 55 65 56 44 10 23 20 34 38 9
‘‘Constantly’’ or ‘‘near constantly’’ affected was defined as those respondents who indicated a 4 or 5 rating on a 5-point scale, where 1 is never and 5 is
constantly.
respectively, based on x2). At least half of respondents of
all age ranges reported that psoriasis resulted in embar-
rassment, inconvenience, and self-consciousness.
psoriasis in Canada, this study describes the demographics
and disease burden of a population of Canadians reporting
moderate-to-severe disease. Respondents reported gender-
specific differences in the age at onset and clinical features,
as well as age-specific differences in the prevalence of
symptoms and comorbid conditions. In addition to
physical impairment, respondents indicated a psychosocial
impact of disease and a reduced quality-of-life.
Survey respondents were largely middle-aged or older
(mean 49.7 years), consistent with the age distribution of a
similar panel-based survey in the United States39 and
offering insight into the longer-term burden of disease.
Respondents were mainly female, in contrast to reports
that psoriasis is equally common in both genders, although
exceptions are documented.11,28,40 The mean age at onset
(25.6 and 30.0 years for females and males, respectively)
was consistent with reports that psoriasis generally appears
between the ages of 15 and 30 years,28 and earlier in
females than males,28,41 but did not demonstrate an
anticipated bimodal distribution.1 Family history and race
of respondents were not reported on, although previous
epidemiologic studies support a genetic basis for disease42
and a difference in the prevalence of psoriasis between
racial groups.7,30
involvement of $ 3% compared to females, consistent
with reports of a greater extent and/or severity of psoriasis
in males, although differences between genders are not
found in all studies.43–46 Although BSA involvement is a
valuable measure for estimating plaque coverage, it may
not fully capture the level of impairment perceived by the
patient.47 Other factors contributing to impairment in
psoriasis include the localization of plaques to visible or
sensitive regions of the body, physical disability (eg, owing
to psoriasis of the hand), psychosocial impact, and
decrement to quality of life.3,32,33,39,47–51 Nail dystrophy
and PsA are associated with pain and disfigurement in
individuals with psoriasis,28 suggesting substantial physical
and psychosocial burdens in many respondents of the
study, particularly within the older age ranges.
Feelings of embarrassment, inconvenience, and self-
consciousness reported by respondents are consistent withT ab
le 5.
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previous studies39,50,52 and highlight the considerable
subjective impact of psoriasis on the overall burden of
disease.53 A negative impact of psoriasis on quality of life
was supported by the clinically meaningful reduction in
SF-8 scores (MCS and PCS)36–38 from the population
norm and reporting of a moderate or greater effect on the
lives of 39% of respondents as detected by the DLQI.
Previously, SF-36 results demonstrated psoriasis to exert a
significant negative effect on quality of life, to an extent
comparable to conditions including hypertension, dia-
betes, heart disease, and depression.54
The high prevalence of high blood pressure, dyslipide-
mia, and obesity or overweight relative to other comor-
bidities is consistent with an association between psoriasis
and inflammatory conditions (eg, metabolic syndrome and
cardiovascular disease)55–58 and the increased prevalence
of these conditions in middle-aged and older Canadians.59
Depression and anxiety were the only reported comorbid-
ities that did not increase in prevalence with age, consistent
with US national survey data demonstrating that emo-
tional suffering owing to psoriasis is more common in
younger (ages 18–34 years) compared to older indivi-
duals.39
from the Ipsos I-Say database approximated that of the
general Canadian population,5,6 although the limitations
to this calculation include a sample bias that may select for
females over males and/or underestimate the proportion of
visible minorities and a response or self-selection bias that
may arise from the voluntary nature of the questionnaire.
Responses to the questionnaire relied on self-report and
were not substantiated through dermatologic evaluation or
patient record. Although self-reports in population surveys
are found to be reasonably accurate for chronic condi-
tions,60 inappropriate recall of diagnoses may have
occurred, as well as an inability to discriminate psoriatic
plaques from skin conditions with similar features.1
Although an Internet panel design is valuable for gathering
epidemiologic evidence on the burden of psoriasis and
natural course of disease by compiling data in a relatively
short time and at low cost,61 sample selection for the
online survey may bias for individuals who are computer
literate, have Internet access, are available to perform
surveys on a volunteer basis, have a higher burden of
disease, are more frustrated over their condition,62 and are
female over male.9 An age-related sample bias may skew
toward older individuals compared to the national average
as such persons may be more likely to respond to survey
questionnaires. Although quality of life measures in the
survey included both a generic and a skin-specific
component for a comprehensive assessment,63 develop-
ment of an instrument with greater sensitivity for
capturing the burden of psoriasis while minimizing floor
and ceiling effects would be valuable.
Conclusions
acteristics, clinical features, and impact of disease in a
population of Canadians reporting moderate-to-severe
plaque psoriasis. The findings are consistent with a
substantial physical and psychosocial impairment attrib-
uted to psoriasis and associated comorbidities and provide
important insights into the burden of disease. Future
research would benefit from replication of current findings
through a national probability study as well as a long-
itudinal assessment of the burden of psoriasis in Canadian
patients.
Acknowledgments
We would like to thank John Howell for support in the
development and editing of the manuscript. We would
also like to acknowledge the support of Fernando
Comacho for additional statistical analysis.
Financial disclosure of authors: This survey was
supported by Janssen-Ortho Inc. Dr. Papp is a consultant
for Janssen-Ortho Inc. Dr. Poulin has been a speaker’s
bureau member and/or trialist for Amgen-Wyeth, Abbott,
Centocor, Schering, Janssen-Ortho Inc. Bristol Myers
Squibb, Calgene, LeoPharma, and Pharmascience. Dr.
Bernstein is a consultant for Janssen-Ortho Inc. Dr. Wasel
has been a consultant, speaker, and/or honorarium
recipient for Abbott, Amgen, Astellas, Biogen, EMD
Serono, Isotechnika, Janssen-Ortho Inc., LEO Pharma,
Schering, and…