Understanding and Predicting a Complex Behavior Using n-of-1 Methods: Photoprotection in Xeroderma Pigmentosum

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 (a) understand and categorize the behavioral complexity and within-participant variability in photoprotection of the face in XP; (b) determine the predictors of photoprotection; and (c) identify individual needs for personalized interventions. Method: A total of 20 adults with XP completed an ecological momentary assessment (EMA) study over 50 days. Measures included an ultraviolet radiation diary of photoprotective behaviors used at each outdoor occasion (e.g., hat, face visor, sunscreen), and a mobile phone survey assessing self-reported protection (0 - 100), satisfaction with protection achieved, and predictive variables (e.g., motivation, effort, mood). Descriptive statistics for photoprotective behavior were computed, per person. When possible, individual dynamic logistic regression models were used to investigate the predictors of photoprotection, and correspondence between self-reported protection and behavior. Results: Photoprotection (clothing and sunscreen) was suboptimal for most participants, and discrepancies between self-reported protection and behavior were identified. Modeling of photoprotection was conducted for six participants who went outside sufficient times and used varied protection. Different predictors were identified across participants. Weekend versus 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 behavioral outcomes and intervention targets to improve photoprotection. The method of profiling multiple preventive behaviors using EMA may be of use in other rare conditions involving complex behaviors.