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British Journal of Health Psychology (2019)
©2019 The Authors. British Journal of Health Psychology published by
John Wiley & Sons Ltd on behalf of British Psychological Society
www.wileyonlinelibrary.com
Psychological correlates of adherence to
photoprotection in a rare disease: International
survey of people with Xeroderma Pigmentosum
Jessica Walburn
1
*, Martha Canfield
2,3
*, Sam Norton
2,3
,
Kirby Sainsbury
4
, Vera Ara
ujo-Soares
4
, Lesley Foster
5
,
Mark Berneburg
6
, Alain Sarasin
7
, Natalie Morrison-Bowen
8
,
Falko F. Sniehotta
4
, Robert Sarkany
5
and John Weinman
1
1
School of Cancer and Pharmaceutical Sciences, Faculty of Life Sciences and Medicine,
King’s College London, UK
2
Health Psychology Section, Institute of Psychiatry, Psychology and Neuroscience,
King’s College London, UK
3
Department of Inflammation Biology, Faculty of Life Sciences and Medicine, King’s
College London, UK
4
Faculty of Medical Sciences, Institute of Health and Society, Newcastle University, UK
5
National Xeroderma Pigmentosum Service, Guy’s and St. Thomas’ NHS Foundation
Trust, London, UK
6
Department of Dermatology, Universit€
atsklinikum Regensburg, Germany
7
Institute of Cancer and Genetics, Gustave Roussy Institute, UMR8200 CNRS,
Villejuif, France
8
School of Medicine, University of Leeds, UK
Objectives. Xeroderma pigmentosum (XP) is an extremely rare genetic disorder
(approximately 100 known cases in the United Kingdom), where DNA damage caused by
ultraviolet radiation in daylight cannot be repaired. Adherence to photoprotection is
essential to prevent skin cancer. We investigated psychological correlates of photopro-
tection in the XP population of Western Europe and the United States.
Design. Cross-sectional survey of adults with XP and caregivers of patients <16 years
and those with cognitive impairment in the United Kingdom, Germany, the United States,
and France (n=156).
Methods. Photoprotection activities to protect the face and body when outdoors;
avoidance of going outside during daylight hours; intention; self-efficacy; and social
This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and
reproduction in any medium, provided the original work is properly cited.
*Correspondence should be addressed to Jessica Walburn, Clinical Practice and Medication Use Group, School of Cancer and
Pharmaceutical Sciences, King’s College London, 150 Stamford Street, London SE1 9NH, UK (email: jessica.2.wal-
burn@kcl.ac.uk).
or
Martha Canfield, Department of Psychology, Institute of Psychiatry, Psychology and Neuroscience (IoPPN), King’s College London,
5th Floor Bermondsey Wing, Guy’s Hospital Campus, London SE1 9RT, UK (email: martha.canfield@kcl.ac.uk).
DOI:10.1111/bjhp.12375
1
support were assessed using measures developed for this study. Participants answered
questions about their illness representations of XP (BIPQ); beliefs about photoprotection
(BMQ); automaticity (i.e., without conscious effort) (SRBAI); clinical and demographic
characteristics. Ordinal logistic regressions determined factors associated with photo-
protection.
Results. One third did not achieve optimal face photoprotection. After controlling for
demographic and clinical factors, modifiable correlates of higher photoprotection
included greater perceived control of XP, stronger beliefs in necessity and effectiveness of
photoprotection, and higher intention. Avoidance of going outside was associated with
greater photoprotection concerns, more serious illness consequences, and higher XP-
related distress. Greater automaticity and higher self-efficacy were associated with better
protection across all outcomes.
Conclusions. Approximately half of all known cases across three European countries
participated. Identified modifiable predictors of photoprotection may be targeted by
interventions to reduce the incidence of skin cancers in the immediate future, when a
treatment breakthrough is unlikely.
Statement of contribution
What is already known on this subject?
Adherence to photoprotection in other populations at elevated risk from skin cancer is poor;
however, the level in XP is unknown.
Research across chronic conditions shows that adherence to treatment and lifestyle recommen-
dations are influenced by illness perceptions, self-efficacy, and treatment beliefs.
Studies on photoprotection conducted with the general population have found that perceived risk,
perceptions of ultraviolet radiation (UVR) protection, self-efficacy for the behaviour, and
automaticity (behaviours that are enacted with little conscious awareness) are related to better
photoprotection.
What does this study add?
This is the first international survey to examine adherence and its correlates in people with XP (an
under-researched group at very high risk of fatal skin cancer). Adherence varies and at least one
third have potential for improvement.
Perceptions about XP, photoprotection beliefs, self-efficacy, intention, and automaticity were
associated with photoprotection of the face and body when outdoors.
Negative emotional representations of XP were associated with avoidance of going outside during
daylight hours.
Xeroderma pigmentosum (XP) is a rare autosomal recessive genetic disorder with an
incidence of 2.3 per million live births in Western Europe (Kleijer et al., 2008), ~100 cases
in the United Kingdom. Individuals cannot repair damage to DNA caused by ultraviolet
radiation (UVR) in daylight. Xeroderma pigmentosum can be broken down into eight
different subtypes, known as complementation groups (A, B, C, D, E, F, G, and V),
corresponding to the eight affected genes involved in the UVR repair pathway (Lehmann,
McGibbon, & Stefanini, 2011). Patients develop skin cancers, often from early childhood,
eye disease, and around 25% of patients have fatal neurological degeneration. The median
lifespan is 32 years, with 60% of prema ture deaths due to malignant melanoma skin cancer
(Bradford et al., 2011). The only way to improve the prognosis is through extremely
rigorous protection against UVR. The aim is to keep UVR exposure to the absolute
2Jessica Walburn et al.
minimum, as there is no known ‘safe’ dose. This is a major burden on patients and their
families, with optimal photoprotection involving UVR-protective face visors, wearing
gloves, hats, and sunscreen, and avoidance of daylight (Tamura, DiGiovanna, Khan, &
Kraemer, 2014).
Despite the importance of photoprotection and the taxing nature of practicing daily
protection, there has been no empirical estimation of levels of adherence to photopro-
tection in XP. An N-of-1 study of our sample showed that adherence varied between and
within individuals (Sainsbury et al., 2018 ) and a qualitative analysis explained this in
terms of differences in individuals’ perceptions of the necessity of photoprotection and its
psychosocial impacts in terms of appearance, self-identity, stigma, and activity restrictions
(Morgan et al., 2019). Adherence is also poor in non-XP survivors of malignant melanoma
(Nahar et al., 2016). In XP, where the risk of melanoma is 2,000-fold greater than the
general population (Bradford et al., 2011), significant non-adherence to photoprotection
substantially increases the risk for morbidity and mortality.
For patients who are non-adherent, the design of effective behaviour change
interventions is required and needs to be informed by knowledge of psychological
factors associated with poor protection. In the general population, photoprotection
behaviour has been associated with beliefs about photoprotection [(e.g., personal
vulnerability, benefits of protection, barriers (Br€
anstr€
om et al., 2010; Pettigrew et al.,
2016)], self-efficacy (Good & Abraham, 2011), intention, and automaticity (behaviours
that are enacted with little conscious awareness)(Allom, Mullan, & Sebastian, 2013). The
importance of treatment beliefs, and to a lesser extent illness perceptions, in explaining
adherence has been reported across other chronic conditions (e.g., Broadbent, Donkin, &
Stroh, 2011; Horne et al., 2013). The related qualitative studies (Anderson, Walburn, &
Morgan, 2017; Morgan et al., 2019) identified a range of determinants (e.g., emotional
distress, appearance concerns, perceived social support), and we wished to explore
whether these associations would be present in a larger representative sample.
The aim of this study was to identify modifiable psychological factors related to
photoprotection activities in XP to inform the development of an intervention designed to
improve photoprotection. This is of considerable importance in XP, where quick
advances in medical treatments are unlikely due to lack of funding (Oo & Rusch, 2016).
Interventions showing improvements in photoprotection among individuals at elevated
risk for melanoma highlight the potential for behaviour change (Wu et al., 2016 –for a
systematic review). Approaches to complex intervention design such as the Behaviour
Change Wheel (Michie, van Stralen, & West, 2011) and Intervention Mapping (Eldredge,
Markham, Kok, Ruiter, & Parcel, 2016) are theory agnostic, and recommend using broad
frameworks based on multiple theories such as Theoretical Domains Framework (TDF)
(Ara
ujo-Soares, Hankonen, Presseau, Rodrigues, & Sniehotta, 2019). Given that this study
is part of formative research informing an intervention for a complex set of behavio urs and
that recent reviews of adherence interventions conclude that no single theoretical model
sufficiently incorporates all known determinants; >700 identified by a review of reviews
(Kardas, Lewek, & Matyjaszczyk, 2013), we selected variables on the basis of the TDF
(Cane, O’Connor, & Michie, 2012) and the updated Common-Sense Model of self-
regulation (CSM) (Leventhal, Phillips, & Burns, 2016). Given that this was the first survey
of psychosocial correlates of adherence in XP, we added variables that the Patient and
Public Involvement (PPI) panel and clinical stakeholders considered to be important (e.g.,
concerns about the impact of photoprotection on family and friends) or had emerged
Adherence to photoprotection in XP 3
within early qualitative interviews (e.g., identity and appearance concerns, social stigma,
and role of social support).
The objectives of the study were threefold: (1) identify levels of adherence to
photoprotection recommendations in XP; (2) describe the beliefs about the condition and
recommended photoprotection regime of people diagnosed with XP; and (3) identify
potentially modifiable psychological factors that might constitute intervention targets.
Methods
Design and participants
This study is part of a mixed-methods programme of research aimed at improving
photoprotection practices in XP patients (Walburn et al., 2017). The cross-sectional
survey was completed between May and December 2016 by 156 participants in the
United Kingdom, France, Germany, and the United States. The target sample size was set
at 193, which represents approximately 80% of known cases in the United Kingdom,
France, and Germany. This target sample size would have allowed detection of
correlations 0.2 (80% power; 5% alpha) and, in hierarchical ordinal logistic regression
models, psychological variables that explained at least an additional 5% of the variance
(i.e., adjusted odds ratio’s >2.4) after initially controlling for clinical and demographic
factors (>90% power; 5% alpha). Due to lower than anticipated recruitment rates,
additional patients were recruited from the United States. The overall recruitment rate
was 57.3% of those invited (the United Kingdom 84.6%, France 70.7%, Germany 72%, and
the United States 40.5%). It is important to accentuate that even though the sample size of
156 participants is small, it represents approximately half of known cases across three
countries in Western Europe, mitigating this weakness.
Procedure
In the United Kingdom and Germany, people diagnosed with XP were invited to
participate by research staff working in the Specialist XP Clinics in London and
Regensburg, respectively. Participants were sent an invitation letter and information
sheet or, if they were due to attend the clinic, were approached in person. In France and
the United States, patients were invited to participate via patient support groups by post
or at scheduled events. Patients were from several regional areas within the countries. All
participants over the age of 16 years gave fully informed consent, apart from in the United
Kingdom where due to REC requirements we also obtained assent (<18 years). For
patients under the age of 16 and/or people with cognitive impairment, we obtained
consent from their parent or caregiver. The study was approved by the relevant ethical
and regulatory bodies (the UK: London –Camden & Kings Cross Research Ethics
Committee 15/LO/1355 (FRA: Authorization was given by the Agence de Biom
edecine
and by the Commission Nationale de l’ Informatique et des Libert
es to Alain Sarasin;
GER: Approved by the local ethics committee at the Universit€
atsklinikum Regensburg;
the USA: Permission was covered by existing data protection legislation). Adult patients
without cognitive impairment completed the survey without assistance. For all children
(<16 years) and adults with significant cognitive impairment, the patient’s primary
caregiver completed the survey about the patient, referred to as ‘the cared-for sample’.
The term ‘adult sample’ refers to patients aged 16 years or above without cognitive
impairment.
4Jessica Walburn et al.
Measures
Two versions of the survey were devised: one for the adult sample and one for the cared-
for sample. The cared-for sample version assessed identical determinants of photopro-
tection to the adult version, the difference being in the phrasing of the question, framed in
relation to the caregiver (e.g., How often do you/does he or she wear a face visor? How
much do you think XP treatment in the clinic (e.g., surgery, creams) can help your/their
skin or eye health?). The survey was developed in English and translated to French and
German using forward and backward translation to achieve equivalence of meaning
(WHO, 2018).
Photoprotection activities
Due to the extreme nature of protection required in XP, and lack of an appropriate
existing questionnaire, a bespoke assessment of photoprotection was developed for the
study (Canfield et al., 2018).
The questionnaire comprised two subscales: a fourteen-item subscale about
adherence to photoprotection to the face (seven items regarding cloudy days and
seven items regarding sunny days) and a ten-item subscale about adherence to
photoprotection to the body (five items for each of cloudy and sunny days).
Participants are asked to report how often, whilst outside, in the last seven days they
wore/used: a face visor, hat, glasses, sunscreen on the face, on the arms/hands and
legs, lips sunscreen, scarf or face-buff, hoodie (worn up), long sleeves, gloves, and
long trousers/thick tights. Responses ranged from 1 (Never) to 5 (Always). A
framework for scoring adherence to face photoprotection was created to avoid
penalizing one photoprotection activity over another (e.g., if wearing a face visor,
there is no benefit from wearing a scarf underneath). The seven individual behaviours
associated with face photoprotection were combined and reduced into five observed
scores based on regions of the face: forehead (face visor, hoodie, face sunscreen),
lower face (face visor, scarf, lips sunscreen), nose (face visor, face sunscreen), cheeks
and sides (face visor, face sunscreen), and eyes (face visor, sunglasses) for both
cloudy and sunny days. Similarly, adherence to body photoprotection behaviours was
defined by the sum of two body areas: arms (long sleeves and sunscreen on the
arms/hands) and legs (long trousers and sunscreen on the legs) for both cloudy and
sunny days. Adherence to face/body photoprotection behaviours was defined by the
sum of the areas and an average score between both cloudy and sunny days. The
maximum score for each scale was 5, indicating optimal photoprotection. No safe
level of UVR exposure for people diagnosed with XP has been identified; therefore,
any score below 4 (indicating moderate to no photoprotection) is interpreted as non-
adherent to recommendations. Internal reliability assessed using Cronbach’s alpha,
for both face and body scales, was high (a=.93 and a=.88, respectively). For the
UK sample (not assessed in other countries), adherence to face photoprotection
correlated highly with an objective measure of average daily facial photoprotection
(r=.66). For further information about the development and validation process of
this measure, see (Canfield et al., 2018).
The extent to which participants avoided going outside during the day was measured
separately on two Likert scale items, one for cloudy days and one for sunny days, ranging
from 1 (Never) to 5 (Always). The total score for avoidance of going outside was defined as
the average of the two items.
Adherence to photoprotection in XP 5
Potential correlates of photoprotection activities
Demographics. Information about gender, age, and education level (ranging from 0, no
qualification, to 5, postgraduate degree), was collected.
Clinical characteristics. Respondents were asked their age at the time of diagnosis,
whether they ever had a diagnosis of any skin cancer, neurological manifestations of the
XP (hearing, walking, cognition, or speaking), eye disease, and XP genetic complemen-
tation group. Since some patients experience an enhanced sunburn response, they were
classified as ‘burners’ if they responded positively to at least two of three items regarding
how easily they sunburn (e.g., Have you ever had sunburn so badly you needed to see a
doctor about it?Yes/no) (Sethi et al., 2013).
Psychological characteristics
Perceptions of photoprotection. Perceptions relating to the need for photoprotection
(an umbrella term for all protection activities) were measured using a modified version of
the Beliefs about Medicines Questionnaire (BMQ) (Horne, Weinman, & Hankins, 1999)
necessity and concerns subscales. Each item is scored on a five-point scale from 1
(Strongly disagree) to 5 (Strongly agree). The average score across items in each subscale
was used in the analysis. Cronbach’s alpha was .73 and .80 for necessity and concerns,
respectively.
Effectiveness of photoprotection behaviours. Participants were asked to report to what
extent they believed their activities had effectively protected against UVR in the last
7days(Thinking about all the things you did to protect yourself over the past 7 days
(e.g., wearing sunscreen, wearing a hat), how well do you think they protected you
from UVR?). Responses ranged from 1 (Not at all)to5(Completely).
Beliefs about XP. An adapted version of the nine-item Brief Illness Perception
Questionnaire (BIPQ) (Broadbent, Petrie, Main, & Weinman, 2006) was used to assess
the following dimensions of patients’ perceptions of their XP: consequences, timeline,
personal control of XP, photoprotection control of XP, treatment control, identity,
negative emotional representation, and perceived understanding, using single items. Each
item is scored on an 11-point scale (0–10), control and perceived understanding items are
reverse scored, with higher scores representing a stronger and more negative perception
of each specific dimension.
Intention to photoprotect. A 10-item questionnaire was designed to measure intention
(motivation) to engage in photoprotection activities when outside. Participants were
asked to report their level of intention for each type of photoprotective activity in the next
7 days (wearing a face visor; hat; glasses; sunscreen; lip sunblock; hoodie; long sleeves;
gloves; long trousers/thick tights) separately (e.g., I intend to protect myself by wearing a
face visor). Responses range from 1 (Strongly disagree)to7(Strongly agree). The mean
score across items was used in the analysis (Cronbach’s alpha, a=.73). Intention to avoid
6Jessica Walburn et al.
going outside during the daytime in the next 7 days was assessed with a single item (I
intend to protect myself by avoiding going outside in the daytime). Responses range
from 1 (‘Strongly disagree’) to 7 (‘Strongly agree’). To facilitate respondent completion of
the questionnaire, the format of these and the self-efficacy items (see below) were adapted
from a manual for designing questionnaires based on the Theory of Planned Behaviour
(Francis et al., 2004), which distils current evidence on how best to operationalize
intention and perceived behavioural control which is conceptually similar to self-efficacy.
Self-efficacy for photoprotection activities. Confidence to protect against UVR was
assessed by 10 items using a similar structure. Participants were asked to report how
confident they were that they would be able to carry out each photoprotection activity
over the next 7 days (e.g., When I am outside in the next 7 days I am confident I could
wear a face visor) using a Likert scale ranging from 1 (‘Strongly disagree’)to7(‘Strongly
agree’). The mean score across items was used in the analysis (Cronbach’s alpha, a=.75).
Confidence to avoid going outside during the daytime in the next 7 days was assessed
using the same Likert scale.
Automaticity of photoprotection activities. Participants were asked to rate the extent
to which they thought that they were carrying out each photoprotection activity
automatically, every time they were ready to go outside over the last 7 days (e.g., Wearing
a hat was something I did automatically without thinking). Responses range from 1
(Strongly disagree that the behaviour was automatic)to7(Strongly agree that the
behaviour was automatic). The item stem was adapted from the Self-Report Behavioural
Automaticity Index (SRBAI) (Gardner, Abraham, Lally, & de Bruijn, 2012) a subscale from
the Self-Report Habit Index (Verplanken & Orbell, 2003) and selected as index of
automaticity (B. Gardner, personal communication, 17 November 2016). The mean score
across items was used in the analysis (Cronbach’s alpha, a=0.71). The extent to which
participants avoided going outside automatically in the previous 7 days was assessed
using the single item (Avoiding going outside during the day was something I did
automatically without thinking) with the same 1–7 Likert scale.
Perceived social support. Level of perceived support with UVR protection was
measured by the mean of two items: amount (How much support or help do you have
from the people around you with your UV protection?) and quality of support (How
satisfied are you with the support or help that you have to help you with your UV
protection?). These single items represented the two dimensions of support (level and
degree of satisfaction) from the Social Support Questionnaire (SSQ) (Sarason, Levine,
Basham, & Sarason, 1983). Responses ranged from 1 (No support)to5(Comprehensive
support).
Analysis
Descriptive statistics were calculated using frequencies and percentages for categorical
data, and means and standard deviations for continuous data. The association between
psychological variables with adherence to face photoprotection, body photoprotection,
and avoidance of going outside was examined in univariate ordinal logistic regressions.
Adherence to photoprotection in XP 7
Variables with standardized odds ratios ≥1.40 (a small effect, equivalent to a standardized
regression coefficient of .1) on at least one photoprotection outcome (adherence to face
photoprotection; adherence to body photoprotection; avoidance of going outside) in the
univariate analyses were entered in ordinal logistic regressions to ascertain the strength of
associations with photoprotection outcomes when adjusted for demographic (age,
gender, country, skin colour) and clinical variables (age at time of diagnosis, history of skin
cancer, and burn status). The amount of variance explained by demographic, clinical, and
potentially modifiable psychological variables in each photoprotection outcome was
assessed in a series of hierarchical ordinal logistic regressions. In each case, the
demographic and clinical variables were entered in the first step and all psychological
variables were entered in the second step.
Results
Adherence to photoprotection recommendations
Table 1 presents the sample characteristics for the total sample (N=156). Using the total
score, photoprotection adherence was higher for the body (M=4.2 out of 5; SD =1.0)
than for the face (M=3.7; SD =1.2). The mean score for avoidance of going outside was
M=2.9 (SD =1.2). There was a strong association between face and body photopro-
tection (r=.77) but weak associations with either face or body photoprotection and
avoidance of going outside (r=.14 and r=.06, respectively).
One third (35.3%) reported suboptimal adherence to face photoprotection. Face
photoprotection was higher on sunny (M=4.27, SD =1.04) compared to cloudy days,
M=4.01, SD =1.28, F(4, 149) =140.5, p<.001, with the largest weather-dependent
difference for sunscreen use (47.4% used on cloudy, 59.6% sunny days). The cared-for
sample was better protected than the adults on the face (M=4.19, SD =0.73 vs.
M=2.89, SD =1.22) and body (M=4.65, SD =0.63 vs. M=3.70, SD =1.10). A
minority of adults wore a visor (32.4%), whereas a large proportion of the cared-for sample
used it on sunny days (85.9%).
Psychological characteristics of the sample
The psychological characteristics are reported in Table 1. The BIPQ scores showed that
participants perceived XP to have serious consequences, to be a chronic condition that
could be effectively managed by treatment, and with a moderate negative emotional
response. Overall, current photoprotection was perceived to be an effective barrier from
UVR, with 66.2% reporting they were ‘completely’ or ‘very well’ protected. Beliefs about
the necessity of photoprotection were high (M=4.41 out of 5, SD =0.72), and there was
less concern about having to photoprotect (M=2.98, SD =0.99). Participants reported
strong intention to photoprotect (M=5.10 out of 7, SD =1.19) and were generally
confident that they could carry out photoprotection (M=5.20, SD =1.21).
Compared to adult patients, caregivers perceived XP to be more serious, were more
convinced that photoprotection could control the condition, reported having a lower
understanding of XP, and felt it had a greater negative emotional impact on the patient.
Caregivers thought protection was more necessary and effective, although had more
concerns. Caregivers also reported stronger intention to protect the person they were
caring for, higher self-efficacy, and greater automaticity than adults.
8Jessica Walburn et al.
Factors associated with photoprotection activities
Univariate results can be found in the Table S1. Considering only the adult sample,
younger chronological age and younger age at diagnosis were associated with increased
photoprotection to the face (OR =.61, p<.05; OR =.59, p<.05) and body (OR =.68,
p<.05; OR =.74, p<.05). Education (adult patients only) was not associated with
photoprotection to the face or body. Clinical factors, including higher propensity to burn
and prior skin cancer, were not significantly related to photoprotection when outdoors or
avoidance of going outdoors.
After controlling for demographic and clinic factors (Table 2), perceptions of greater
personal control over the health impact of XP (OR 1.72, 95% CI 1.20, 2.45; OR 1.63, 95% CI
1.15, 2.30), greater perceived photoprotection control of XP (OR 1.64, 95% CI 1.19, 2.26;
OR 1.39, 95% CI 1.02, 1.90), stronger belief in the necessity of photoprotection (OR 1.88,
95% CI 1.34, 2.64; OR 2.09, 95% CI 1.46, 2.99), and effectiveness of protection against
UVR (OR 2.22, 95% CI 1.53, 3.24; OR 2.09, 95% CI 1.39, 2.76), and greater intention to
photoprotect (OR 1.83, 95% CI 1.28, 2.61; OR 1.59, 95% CI 1.14, 2.20) were significantly
associated with higher adherence to face and body photoprotection but not related to
avoidance of going outside. In contrast, higher XP-related distress (OR 2.11, 95% CI 1.54,
2.89) and concern (OR 1.65, 95% CI 1.20, 2.25), stronger belief that XP has serious
consequences (OR, 1.47, 95% CI 1.09, 1.99) and greater concerns about protecting
against UVR (OR 1.80, 95% CI 1.32, 2.46),were all significantly associated with avoidance
of going outside, but not related to adherence to face or body photoprotection (except
consequences for the latter). Self-efficacy was related to all photoprotection outcomes
(OR 1.83, 95% CI 1.28, 2.61; OR 1.68 , 95% CI 1.20, 2.12; OR 2.20, 95% CI 1.61, 3.00;
adherence to face and body photoprotection and avoidance of going outside,
respectively) as was automaticity (OR 2.16, 95% CI 1.47, 3.19; OR 2.20, 95% CI 1.52,
3.18; OR 2.52, 95% CI 1.82, 3.49; adherence to face and body photoprotection and
avoidance of going outside, respectively).
Hierarchical multivariable ordinal logistic regressions examined the amount of
variance explained by all potentially modifiable psychological factors identified in the
previous analysis (Table 2). In the first step, demographic and clinical variables explained
between 1 and 8% of variance in photoprotection behaviour. Psychological variables,
entered in the second step, explained an additional 5% of the variance in avoidance of
going outside, 14% in adherence to face photoprotection, and 17% in adherence to body
photoprotection (all p<.05).
Discussion
This is the first survey of adherence to photoprotection to be conducted in people living
with XP. Reported adherence to photoprotection was suboptimal for around one third of
individuals. Stronger perceptions of the extent to which photoprotection can control the
health consequences of XP, stronger beliefs about the necessity of protecting, higher
intention, self-efficacy, and automaticity were related to better photoprotection whilst
outside. Avoiding exposure by staying indoors was associated with a different pattern of
predictors, with negative emotional representations and concerns about XP and
photoprotection being more important. The range of factors supports the use of unified
frameworks and models that include a wider variety of variables, such as the recent
extension to the CSM by Hagger and colleagues to incorporate attitudes, self-efficacy,
intentions, and action plans (Hagger, Koch, Chatzisarantis, & Orbell, 2017).
Adherence to photoprotection in XP 9
Table 1. Demographic, clinical, psychological, and photoprotection characteristics of the sample
Total (N= 156)
Adult patient
sample (n= 71)
Cared-for sample
(caregivers) (N= 85)
p(adult patient
vs. caregivers)
Demographic variables
Male, n(%) 79 (50.6%) 37 (52.1%) 42 (49.4%) .737
Age, mean (SD) 24.81 (19.46) 39.03 (19.23) 12.94 (8.76) <.001
Skin colour (brown/black = 0), n(%) 100 (64.5%) 44 (62%) 56 (66.7%) .543
Education level, n(%)
No qualifications 26 (26.0) 6 (8.7) 20 (64.5%) <.001
Secondary school 12(12.0) 9 (13.0) 3 (9.7%)
Post-school qualification 24 (24.0) 19 (27.5) 5 (16.1%)
Professional qualifications 24 (24.0) 22 (31.9) 2 (6.5%)
Higher education diploma 14 (14.0) 13 (18. 1) 1 (3.2%)
Country, n(%)
UK 66 (42.3) 39 (54.9) 27 (31.8%) .021
France 58 (37.2) 22 (31.0) 36 (42.4%)
Germany 15 (9.6) 6 (8.5) 9 (10.6%)
USA 17 (10.9) 4 (5.6) 13 (15.8%)
Clinical variables
Age at the time of diagnosis, mean (SD) 10.94 (14.73 19.18 (17.74) 4.09 (5.80)
Burners, n(%) 47 (30.1) 18 (25.4) 29 (34.1%) .235
Skin cancer, n(%) 71 (45.2) 45 (63.4) 25 (29.4%) <.001
XP causing cognitive problems, n(%) 35 (22.4) 8 (11.3) 26 (31.0%)
Eyes problems, n(%) 112 (71.8) 50 (70.4) 62 (72.9%) .728
Psychological variables, mean (SD)
Illness perception (0–10)
Consequences 7.24 (2.66) 6.54 (2.85) 7.82 (2.36) .002
Timeline 9.46 (1.69) 9.75 (1.26) 9.22 (1.97) .055
Personal control of XP 6.05 (3.07) 5.89 (2.73) 6.19 (3.34) .544
Photoprotection control of XP 8.87 (1.85) 8.15 (2.28) 9.47 (1.09) <.001
Continued
10 Jessica Walburn et al.
Table 1. (Continued)
Total (N= 156)
Adult patient
sample (n= 71)
Cared-for sample
(caregivers) (N= 85)
p(adult patient
vs. caregivers)
Treatment control 8.15 (2.20) 8.29 (1.99) 8.02 (2.37) .444
Identity 5.74 (3.08) 5.54 (3.13) 5.90 (3.06) .457
Illness concern 6.44 (3.09) 6.48 (3.08) 6.41 (3.12) .893
Understanding 7.14 (2.76) 8.25 (1.73) 6.21 (3.10) <.001
Emotional representation 6.06 (3.24) 5.51 (3.45) 6.53 (3.00) .049
Beliefs about photoprotection (1–5)
Necessity 4.41 (0.72) 4.11 (0.80) 4.66 (0.52) <.001
Concern 2.98 (0.99) 2.79 (0.95) 3.15 (0.99) .024
Intention to photoprotect (1–7) 5.10 (1.19) 4.83 (1.21)) 5.34 (1.12) .010
Intention to avoid going outside 4.34 (2.37) 4.51 (2.39) 4.20 (2.37) .428
Self-efficacy to photoprotect
a
(1–7) 5.20 (1.21) 4.01 (1.21) 5.52 (1.13) .001
Self-efficacy to avoid going outside 4.13 (2.38) 3.93 (2.31) 4.30 (2.45) .342
Automaticity of photoprotection
a
(1–7) 4.44 (1.42) 4.01 (1.39) 4.79 (1.34) .001
Automaticity of avoidance of going outside 4.49 (2.83) 4.23 (2.84) 4.71 (2.82) .293
Social support (1–5) 3.70 (1.16 3.60 (1.02) 3.33 (1.20) .150
Effectiveness of photoprotection
a
(1–5) 3.75 (1.00) 3.47 (.92) 3.96 (1.02) .002
Photoprotection behaviours, mean (SD)
Adherence to face photoprotection practices
a
3.69 (1.17) 2.89 (1.22) 4.19 (.73) <.001
Adherence to body photoprotection practices
a
4.21 (.99) 3.70 (1.10) 4.65 (.63) <.001
Avoid going outside 2.92 (1.21) 3.05 (1.16) 2.82 (1.24) .234
Note.
a
Wearing sunscreen, clothing when outside.
Adherence to photoprotection in XP 11
Table 2. Multivariable logistic regression of photoprotection activities on psychological variables adjusted for demographic and clinical factors
Adherence to face
photoprotection
OR (95% CI) p
Adherence to body
photoprotection
OR (95% CI) p
Avoidance of
going outside
OR (95% CI) p
XP Illness perception
Consequences 1.25 (0.86, 1.81) .238 1.42 (1.01, 1.99) .038 2.11 (1.54, 2.89) <.001
Personal control of XP 1.72 (1.20, 2.45) .003 1.63 (1.15, 2.30) .005 0.77 (0.56, 1.05) .097
Photoprotection control of XP 1.64 (1.19, 2.26) .002 1.39 (1.02, 1.90) .036 0.99 (0.73, 1.34) .953
Illness concern 0.96 (0.66, 1.39) .830 1.10 (0.79, 1.55) .555 1.65 (1.20, 2.25) .002
Understanding 0.92 (0.81, 1.05) .223 0.90 (0.80, 1.02) .110 0.94 (0.84, 1.09) .262
Emotional representation 1.24 (0.88, 1.75) .219 1.32 (0.95, 1.84) .098 1.47 (1.09, 1.99) .011
Beliefs about photoprotection
Necessity 1.88 (1.34, 2.64) <.001 2.09 (1.46, 2.99) <.001 1.33 (0.98, 1.81) .066
Concern 1.14 (0.80, 1.64) .455 1.05 (0.65, 1.70) .846 1.80 (1.32, 2.46) <.001
Intention to photoprotect
a
/avoid going out 1.83 (1.28, 2.61) .001 1.59 (1.14, 2.20) .005 1.09 (0.86, 1.37) .483
Self-efficacy of photoprotection
a
/avoid going out 1.83 (1.29, 2.60) .001 1.68 (1.20, 2.12) .002 2.20 (1.61, 3.00) <.001
Automaticity of photoprotection
a
/avoid going out 2.16 (1.47, 3.19) <.001 2.20 (1.52, 3.18) <.001 2.52 (1.82, 3.49) <.001
Effectiveness of photoprotection
a
2.22 (1.53, 3.24) <.001 1.96 (1.39, 2.76) <.001 1.10 (0.82, 1.47) .531
R
2
model for demographic and clinical variables .08 .05 .01
R
2
model for demographic, clinical and
psychological variables .22 .22 .06
Notes. Models adjusted for gender, age, skin type, country, age at time of diagnosis, burning type, and history of skin cancer. Bold indicates statistically significant
associations.
a
Wearing sunscreen, clothing when outside.
12 Jessica Walburn et al.
Automaticity, a feature of but not limited to habitual behaviour (Marteau, Hollands, &
Fletcher, 2012), was an important determinant for better photoprotection outdoors and
avoiding daylight altogether. These findings support the targeting of automatic alongside
deliberative processes and are consistent with phase models of behaviour, which include
volitional and motivational constructs [e.g., Health Action Process Approach, (Schwarzer,
2008)]. Previous studies of photoprotection behaviour in student samples have reported
positive relationships (Allom et al., 2013) as have adherence studies in other chronic
conditions (Durand et al., 2018; Phillips, Cohen, Burns, Abrams, & Renninger, 2016). The
development of habitual photoprotection could contribute to the negative association
between age at the time of diagnosis and adherence in adults. Behaviour changes started in
childhood might encourage the development of habit and greater acceptance of the
necessity of photoprotection. As photoprotection is performed daily, this facilitates habit
formation where repetition of behaviours in the same context is key (Lally, van Jaarsveld,
Potts, & Wardle, 2010). Automatic processes might be especially important, as
photoprotection is likely to be triggered by environmental cues such as sunlight
(Andersen et al., 2016). Future research needs to investigate longitudinally the relative
importance of beliefs versus habitual drivers in photoprotection maintenance.
Consistent with findings in the wider literature, illness- and treatment-related
cognitions, especially necessity beliefs, were related to adherence in XP. This supports
the utility of treatment beliefs to explain variation in preventative behavioural regimes, as
well as adherence to prescribed medicines (Foot, La Caze, Gujral, & Cottrell, 2016). Few
studies have investigated the relationship between perceptions of skin cancer and
protection activities. Cameron (2008) studied illness risk representations of skin cancer in
a student sample and found that beliefs in weak treatment control were associated with
better protection. We found personal rather than treatment control to be more important,
perhaps due to robust measurement of photoprotection and control of clinical
confounders. Those with greater concerns about photoprotection activities have a
stronger tendency to avoid going outside during the day. It seems likely that greater
concerns about wearing photoprotective clothing/sunscreen may tip the balance towards
staying indoors, which may be a more acceptable way of coping for some individuals. It is
noteworthy that having a negative emotional representation of XP was associated with
staying indoors. Given the cross-sectional design, we do not know whether this is driven
by photoprotection preferences or whether it is a consequence of emotional distress. The
burden of living with XP includes stigma related to changes in appearance, constant UVR
monitoring, and worries about skin cancer (Anderson et al., 2017; Morgan et al., 2019).
Further research needs to investigate the prevalence of emotional distress associated with
photoprotection in XP to ascertain if there is something intrinsic about photoprotection
that is detrimental to well-being.
Staying indoors is not actively encouraged by the clinical teams as it is not a feasible
option for all and contrary to the team’s wish to promote quality of life within the confines
of extreme photoprotection. This is reflected in the findings as participants protected
themselves more frequently by using sunscreen and clothing. In addition, avoidance of
outdoors is more influenced by the context of peo ple’s lives and demands of work, school,
and other external constraints. This is supported by the finding that little variance was
explained in the final model of avoidance of going outside, suggesting that it has different
determinants not measured here (e.g., occupation). The importance of these contextual
factors in adherence is emphasized by a recent OECD report (Khan & Socha-Dietrich,
2018). If the study were to be replicated in non-Western low- and middle-income
Adherence to photoprotection in XP 13
countries, their different health care systems and sociocultural environments should be
considered.
Adherence in the cared-for sample was higher than in the adults, which could be
explained by the impact of having somebody monitoring and helping patients to meet
their health needs. Whilst this could potentially be a reporting bias, a number of
psychological correlates exhibited by caregivers are consistent with those found to be
more favourable to adherence to photoprotection in other populations including higher
self-efficacy (Craciun, Sch€
uz, Lippke, & Schwarzer, 2012), stronger intention (Starfelt
Sutton & White, 2016), and greater automaticity (Allom et al., 2013). Although the cared-
for sample reported higher photoprotection, social support, in terms of both the
perceived level and quality of support, in the whole sample was not related to adherence.
Given the growing literature on the importance of perceived social support in treatment
adherence (DiMatteo, 2004; Scheurer, Choudhry, Swanton, Matlin, & Shrank, 2012) and
the complexity of the interactions between provider and recipient, future qualitative
research is required to explore how social support influences photoprotection activities
from the perspective of the XP patient.
Limitations and future research
There are a number of limitations to the present study. Naturally, the cross-sectional
design means that causality cannot be ascertained and we are investigating the
relationship between current psychological factors and past rather than future
behaviour. Further prospective studies are recommended to investigate change in
variables over time, although recent longitudinal photodermatological research in a
healthy population (Thieden, Holm-Schou, Philipsen, Heydenreich, & Wulf, 2019) and
data from a related N-of-1 study carried out over 50 days suggest that UVR exposure and
photoprotection are relatively stable within individuals (Sainsbury et al., 2018). Due to the
modest overall variance explained in photoprotection, we also speculate whether the
questionnaire missed other psychological correlates, such as those which have since been
identified by related qualitative research (e.g., resistance to XP identity; Morgan et al.,
2019). Concerns about questionnaire length voiced by the PPI panel were a contributing
factor to the decision to limit constructs measured and use shortened versions. Another
limitation is that adherence is likely to be lower than observed since we used a self-report
measure. A validation of our bespoke adherence tool against UVR dosimetry over a three-
week period indicated that whilst those reporting suboptimal adherence typically did not
protect well against UVR, there was greater variability in UVR protection for those self-
reporting high adherence (Canfield et al., 2018).
Due to the rarity of the condition, it was necessary to recruit from a number of different
countries. Whilst this may enhance the generalizability of our findings, this relies on there
being no differences in the strength of the association between predictor variables across
countries (i.e., no country by predictor interaction). The sample size limited the
possibility to analyse photoprotection differences between countries. Given the
challenges of recruiting participants in rare disease research (Kwakkenbos et al., 2013;
Sainsbury, Walburn, Araujo-Soares, & Weinman, 2018), we had to extend the data
collection period beyond the summer months (May to December 2016) and seasonal
differences might have had an influence on some responses. Despite these limitations, this
is the only survey that has collected internationally comparable quantitative data in people
diagnosed with XP. It is unlikely that larger studies are feasible in the target countries due
to the response rate of 57% of those invited already being included here.
14 Jessica Walburn et al.
Implications for intervention design
A number of modifiable psychological factors associated with photoprotection were
identified that may be amenable to intervention. We would recommend that an
intervention incorporates content to strengthen necessity by exploring specific beliefs
that underpin doubts and resolving misunderstandings. Similar techniques have been
effective in other chronic conditions (Broadbent, Ellis, Thomas, Gamble, & Petrie, 2009;
O’Carroll, Chambers, Dennis, Sudlow, & Johnston, 2013). Communicating the cumulative
nature of UVR damage would be particularly important. To maximize efficacy, resultant
elevation of perceived threat should be accompanied by content to emphasize response
efficacy (Tannenbaum et al., 2015). Promotion of habitual photoprotection by anchoring
new behaviours to existing habits, creating environmental cues, and repeating in the same
context should be included (Gardner, 2015). The reduced photoprotection on cloudy days
reported here has serious implications for patients since UVR damage is still incurred and
cloudy days are frequent in Western Europe. Therefore, we suggest that content related to
psychological drivers are linked to weather conditions (e.g., emphasizing that external
prompts to protect are more important in cloudy weather when there are fewer natural
cues, such as sunlight). Given the complex nature of photoprotection, interventions to
improve photoprotection will need to be tailored both to the individual’s pattern of drivers
and to the particular photoprotection activity, since avoiding going outside and
photoprotection whilst outside are influenced by different factors.
Acknowledgements
We acknowledge the role of the French Association ‘Les Enfants de la Lune’ and the valuable
input of Michele Milota, XP Family Support Group, USA, for giving us the opportunity to
distribute the questionnaire to members of the XP Family Support Group. We acknowledge the
constructive input of the XP national clinical team (Isabel Garrood, Hiva Fassihi, Tanya
Henshaw, Alan Lehmann, Sally Turner), the members of the Patient and Public Involvement
panel (Cathy Coleman, Ben Fowler, Ros Tobin, Sandra Webb) in assisting with development of
the questionnaire. We thank Kate Johnstone and Mariam Babunashvili for assisting with data
entry. Many thanks to Federica Picariello, Lucy Hardy, and Myfanwy Morgan for commenting
on the final draft.
Funding
This study/project is funded by the National Institute for Health Research (NIHR)
[Programme Grant for Applied Research Scheme (RP-PG-1212 20009)]. The views
expressed are those of the author(s) and not necessarily those of the NIHR or the
Department of Health and Social Care.
Conflicts of interest
All authors declare no conflict of interest.
Author contributions
As joint first authors, JWa and MC were equal contributors and all authors reviewed and
commented on the manuscript. All authors (excluding MC) were involved in the study
Adherence to photoprotection in XP 15
design and development of the questionnaire. JW and LF were involved in the translation
of questionnaires and all data collection. MC and SN conducted the analysis assisted by
NM.
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Received 23 November 2018; revised version received 15 April 2019
Supporting Information
The following supporting information may be found in the online edition of the article:
Table S1. Univariate ordinal logistic regression of photoprotection practices on
demographic, clinical and psychological variables.
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Adherence to photoprotection in XP 19
