This observational study has investigated whether patients with psoriasis had the most severely impaired QoL among 13 skin diseases. The data came from the DLOI of a large sample of dermatological patients in China. A total of 8,339 participants were included. The study’s major finding was that patients with psoriasis had worse QoL than patients without psoriasis, even after adjusting for demographic factors and other common health conditions. The sensitivity analysis also showed a high degree of robustness after excluding subjects with acne or eczema.
Previous studies have shown that QoL measured by the DLQI in patients with psoriasis is lower than that of patients with AD, vitiligo or alopecia areata [24–26]. Our findings corroborate these studies. However, a study from Denmark found that patients with AD reported the greatest DLQI impairment among patients suffering from psoriasis and other dermatological diseases, which did not adjust for possible confounding factors to assess whether there was a statistically significant difference . In contrast, another study reported no significant difference between AD and psoriasis when controlling for 4 confounding factors (age, sex, diagnosis and concomitant diseases) . Our study confirmed that patients with psoriasis were associated with worse QoL than patients with other skin diseases, when controlling for 9 factors.
The mean DLQI score for patients with psoriasis in this study was 11.20. This is higher than the previous mean DLQI for subjects with psoriasis in several other studies [17, 32, 33]. However, there have been several studies which have reported lower DLQI means for patients with psoriasis than ours [24–26]. Our results are in accordance with those from studies conducted in China [22, 23]. This demonstrated that our sample was representative. We also analyzed six aspects of the DLQI, and the scores for patients with psoriasis along any aspect were higher than that of those without psoriasis. This was consistent with the above results.
Disease severity was an important factor affecting QoL. The more severe the disease, the higher the DLQI score. A study from Norway and South Africa has demonstrated this [28, 29]. In order to eliminate disease severity’s influence on DLQI scores, we conducted both subgroup analysis and multivariate linear regression. The results showed a statistically significant difference in DLQI scores between the two groups, even if disease severity was controlled.
A major strength of our study is the large study population collected from several large clinical centers. Additional strengths include the assessment with well-validated measurement-DLQI, and the multivariate linear regression model for controlling confounding effects.
This study does have several limitations. Firstly, this cross-sectional study was based on the population of dermatology patients in China, rather than the overall population. Therefore, the prevalence of psoriasis was much higher than that of the general population (15.7% and 0.47%, respectively) . Thus, the likelihood of selection bias is high. Secondly, a cross-sectional study cannot establish causality between psoriasis and QoL. Finally, the judgment of disease severity was not based on specific criteria for each disease, and this may have affected the accuracy. However, qualified dermatologists with standardized training could maintain the comparability.