Understanding and predicting a complex behaviour using n-of-1 methods: Photoprotection in xeroderma pigmentosum

Kirby Sainsbury, Rute Vieira, Jessica Walburn, Falko F Sniehotta, Robert Sarkany, John Weinman, Vera Araujo-Soares

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Objective: Xeroderma pigmentosum (XP) is a very rare inherited disease; the most important aspect of clinical management is rigorous photoprotection from ultraviolet radiation. The aims of this novel study were to: (1) understand and categorize the behavioural complexity and within-participant variability in photoprotection of the face in XP; (2) to determine the predictors of photoprotection; and (3) to identify individual needs for personalized interventions.

Methods: A total of 20 adults with XP completed an ecological momentary assessment (EMA) study over 50 days. Measures included an activity diary of photoprotective behaviours used at each outdoor occasion (e.g., hat, face visor), and a mobile phone survey assessing self-reported protection, satisfaction with protection achieved, and predictive variables (e.g., motivation, effort, mood). Descriptive statistics for photoprotective behaviour were computed, per person. When possible, dynamic logistic regression was used to model the predictors of photoprotection, and correspondence between self-reported protection and behaviour.

Results: Photoprotection (clothing and sunscreen) was sub-optimal for most participants, and discrepancies between self-reported protection and behaviour were identified. Modelling of photoprotection was conducted for six participants who went outside sufficient times and used varied protection. Different predictors were identified across participants. Weekend vs. weekday, physical symptoms, stress, and feeling self-conscious were most frequently associated with protection.

Conclusion: The findings support the need for intervention and have implications for the selection of individually-tailored behavioural outcomes and intervention targets to improve photoprotection. The method of profiling multiple preventive behaviours using EMA may be of use in other rare conditions involving complex behaviours.
Original languageEnglish
Pages (from-to)1145-1158
Number of pages14
JournalHealth Psychology
Issue number12
Publication statusPublished - Dec 2018

Bibliographical note

Acknowledgements: We would like to thank Lesley Foster (research nurse) for all her work in setting up the n-of-1 study with patients; the XP national clinical team (Hiva Fassihi, Tanya Henshaw, Sally Turner, Isabel Garrood, Alan Lehmann) and members of the PPI panel (Cathy Coleman, Ben Fowler, Sandra Webb, Ros Tobin) for input into design of materials.

Funding: This research is funded by the National Institute for Health Research (NIHR) Programme Grants for Applied Research (RP-PG- 1212-20009). The views and opinions expressed therein are those of the authors and do not necessarily reflect those of the NIHR, NHS, or the Department of Health.


  • xeroderma pigmentosum
  • rare disease
  • photoprotection
  • adherence
  • n-of-1
  • ecological momentary assessment


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