Association between sun-protective behaviours and psoriasis in US adults in the National Health and Nutrition Examination Survey, 2009-2014: a cross-sectional study.

OBJECTIVE

To evaluate the association between sun-protective behaviours and psoriasis in a nationally representative sample of US adults.

DESIGN

Analysis of cross-sectional data.

SETTING

National Health and Nutrition Examination Survey (NHANES), 2009-2014.

PARTICIPANTS

A total of 9735 participants aged 20-59 years with available data on psoriasis, sun-protective behaviours and covariates were included in the analysis.

OUTCOME MEASURES

Information on sun-protective behaviours (staying in the shade, wearing long sleeves and using sunscreen) and psoriasis was obtained from questionnaires in the NHANES database. Logistic regression models and subgroup analyses were employed to investigate the association between sun-protective behaviours and psoriasis.

RESULTS

After adjusting for sociodemographic variables, body mass index (BMI), alcohol drinking status, smoking status, sun sensitivity and time spent outdoors in the multivariable logistic regression model, moderate wearing of long sleeves was negatively associated with psoriasis (OR, 0.55; 95% CI 0.33 to 0.90, p=0.02), while frequent wearing showed no significant relationship. There was no significant association between staying in the shade and psoriasis, regardless of frequency. Subgroup analyses stratified by age, gender, race/ethnicity and smoking status revealed no significant associations in most groups, but moderate wearing of long sleeves was found to be negatively associated with psoriasis among those aged 20-39 years (OR, 0.42; 95% CI 0.18 to 0.98, p=0.04), among non-Hispanic white individuals (OR, 0.52; 95% CI 0.28 to 0.97, p=0.04) and among non-smokers (OR, 0.49; 95% CI 0.25 to 0.95, p=0.04), as it was among women in terms of overall sun protection (OR, 0.58; 95% CI 0.35 to 0.97, p=0.04). However, among non-Hispanic white individuals (staying in the shade: OR, 1.69; 95% CI 1.00 to 2.84, p=0.049) and former/current smokers (overall: OR, 3.28; 95% CI 1.41 to 7.63, p=0.009), frequent sun protection was positively associated with psoriasis.

CONCLUSIONS

Moderate sun-protective behaviours among US adults were found to be negatively associated with psoriasis. However, among non-Hispanic white individuals and former/current smokers, frequent sun protection was positively associated with psoriasis. Future studies with rigorous study design could further explore and validate the potential reasons for these associations to better inform evidence-based behavioural recommendations that protect human health.