SummaryBackground Seborrhoeic dermatitis is a chronic relapsing inflammatory skin disease with unclear pathophysiological mechanisms. Objectives To establish which lifestyle and physiological determinants are associated with seborrhoeic dermatitis. Methods Seborrhoeic dermatitis was diagnosed by a trained physician during a full-body skin examination within the Rotterdam Study, a prospective population-based cohort study in middle-aged and elderly people. The current design is a comparative cross-sectional study embedded in the Rotterdam Study. Potential factors were identified from the literature and analysed in a multivariable logistic regression, including: age, sex, obesity, skin colour, stress, depression, education level, hypertension, climate, xerosis cutis, alcohol and tobacco use. Results Of the 5498 participants, 788 participants were diagnosed with seborrhoeic dermatitis (14Á3%). We found associations between seborrhoeic dermatitis and male sex [adjusted odds ratio (OR) 2Á09, 95% confidence interval (CI) 1Á77-2Á47], darker skin (adjusted OR 0Á39, 95% CI 0Á22-0Á69), season (summer vs. winter: adjusted OR 0Á63, 95% CI 0Á48-0Á82) and generalized xerosis cutis (adjusted OR 1Á41, 95% CI 1Á11-1Á80). Conclusions Seborrhoeic dermatitis is one of the most common inflammatory dermatoses in middle-aged and elderly individuals, especially during winter. Men, and people with a light and dry skin were most likely to have seborrhoeic dermatitis.

Current treatments for seborrheic dermatitis provide only temporary relief. Therefore, identifying modifiable lifestyle factors may help reduce disease burden. The objective of this study was to determine whether specific dietary patterns or total antioxidant capacity are associated with seborrheic dermatitis. Participants of the Rotterdam Study with a skin examination and a food frequency questionnaire were included. Total antioxidant capacity was assessed on the basis of ferric reducing antioxidant potential of each food item. Dietary patterns were identified with principal component analysis (PCA). Multivariable logistic regression analyses were used to assess the association between total antioxidant capacity, dietary pattern-derived PCA factors, and seborrheic dermatitis adjusted for confounders. In total, 4,379 participants were included, of whom 636 (14.5%) had seborrheic dermatitis. The PCA identified vegetable, Western, fat-rich and fruit dietary patterns. The fruit pattern was associated with a 25% lower risk (quartile 1 vs. quartile 4: adjusted odds ratio = 0.76, 95% confidence interval = 0.58-0.97, P = 0.03), and the Western pattern with a 47% increased risk (quartile 1 vs. quartile 4: adjusted odds ratio = 1.47; 95% confidence interval = 0.98-2.20, P = 0.03), but only for females. Other factors were not associated with seborrheic dermatitis. In conclusion, a high fruit intake was associated with less seborrheic dermatitis, whereas high adherence to a "Western" dietary pattern in females was associated with more seborrheic dermatitis.

Background Seborrheic dermatitis (SD) is a chronic inflammatory skin disease with a multifactorial aetiology. Malassezia yeasts have been associated with the disease but the role of bacterial composition in SD has not been thoroughly investigated. Objectives To profile the bacterial microbiome of SD patients and compare this with the microbiome of individuals with no inflammatory skin disease (controls). Methods This was a cross sectional study embedded in a population-based study. Skin swabs were taken from naso-labial fold from patients with seborrheic dermatitis (lesional skin: n = 22; non-lesional skin SD: n = 75) and controls (n = 465). Sample collection began in 2016 at the research facility and is still ongoing. Shannon and Chao1 α- diversity metrics were calculated per group. Associations between the microbiome composition of cases and controls was calculated using multivariate statistics (permANOVA) and univariate statistics. Results We found an increased α-diversity between SD lesional cases versus controls (Shannon diversity: Kruskal-Wallis rank sum: Chi-squared: 19.06; global p-value = 7.7x10-5). Multivariate statistical analysis showed significant associations in microbiome composition when comparing lesional SD skin to controls (p-value = 0.03;R2 = 0.1%). Seven out of 13 amplicon sequence variants (ASVs) that were significantly different between controls and lesional cases were members of the genus Staphylococcus, most of which showed increased composition in lesional cases, and were closely related to S. capitis S. caprae and S. epidermidis. Conclusion Microbiome composition differs in patients with seborrheic dermatitis and individuals without diseases. Differences were mainly found in the genus Staphylococcus.

Expanding the COL7A1 mutation database: novel and recurrent mutations and unusual genotype-phenotype constellations in 41 patients with dystrophic epidermolysis bullosa.