Daily itch duration, sleep disturbance, scratching frequency, and average itch intensity mediated the association between disease severity and quality of life among patients with chronic inflammatory skin diseases, with daily itch duration showing the strongest mediating effect.
Researchers conducted a prospective, cross-sectional study involving 522 adult patients with chronic pruritus associated with atopic dermatitis, psoriasis, chronic prurigo, or chronic urticaria recruited from 10 dermatology practices and 2 dermatology clinics in Germany between September 2018 and October 2020. Dermatologists assessed disease severity using disease-specific instruments, and patients completed validated questionnaires evaluating worst and average itch intensity, daily itch duration, scratching frequency, sleep disturbance, and itch-specific quality of life (QoL). To facilitate comparisons across the four conditions, investigators harmonized disease severity into a single categorical measure.
The primary analyses evaluated the associations between disease severity, itch-related measures, and QoL using the 5-Pruritus Life Quality (5PLQ) questionnaire. Researchers then performed multivariable regression and mediation analyses to determine whether itch intensity, daily itch duration, scratching behavior, and sleep disturbance explained the relationship between disease severity and impaired QoL.
Mediation analyses identified daily itch duration as the strongest mediator of the association between disease severity and QoL, followed by sleep disturbance, scratching frequency, and average itch intensity. In contrast, worst itch intensity did not significantly mediate the relationship.
Supporting analyses showed that impaired QoL correlated only weakly with overall disease severity but more strongly with itch-related measures. In multivariable analyses, female sex, moderate disease severity, scratching frequency, and sleep disturbance were independently associated with greater QoL impairment. Compared with patients with psoriasis, those with atopic dermatitis, chronic prurigo, and chronic urticaria had higher QoL impairment.
The investigators noted that average itch intensity appeared more informative than worst itch intensity for understanding impaired QoL. They also highlighted daily itch duration as an important but often underassessed dimension of itch that showed the greatest mediating effect across the analyses, suggesting that evaluating multiple aspects of itch may better characterize disease burden than focusing solely on peak itch intensity.
The authors acknowledged several limitations. The cross-sectional design precludes causal inference; disease severity was harmonized across four diseases using a composite severity measure, chronic urticaria severity was assessed with a nonvalidated investigator global assessment, patient groups were unequal in size, and only adult patients were included, limiting generalizability to pediatric populations.
Overall, the findings suggest that assessing daily itch duration alongside sleep disturbance, scratching behavior, and average itch intensity may provide a more comprehensive understanding of how disease severity relates to QoL in patients with chronic inflammatory skin diseases.
"Assessing these itch-related parameters and addressing them with targeted therapeutic interventions is thus of pivotal importance to improve the quality of life in this complex patient population," wrote lead study author Manuel P. Pereira MD, of Charité–University Medical Center Berlin, and colleagues.
Disclosures: The study was supported by an unrestricted grant from Novartis Pharma GmbH, which had no role in the study design, conduct, analysis, or publication. Several authors reported financial relationships with pharmaceutical companies. Full disclosures are available in the published article.
Source: Dermatology and Therapy
