Actinic keratosis (AK) is a skin condition associated with several risk factors, such as age, sun exposure, and immunosuppression. Certain drugs, such as photosensitizing medications and calcium channel blockers (CCBs), have also been linked to AK. Therefore, his study aims to explore the impact of individual, behavioural, and exposure factors on the severity of AKs on the face and scalp. A multicentre cross-sectional study was conducted on immunocompetent individuals with at least one AK on their face or scalp. The study assessed demographic factors, sun exposure and protection, smoking and alcohol use, personal and family history of skin cancer, and medication use within the last six months. The primary outcome was the Actinic Keratosis Area and Severity Index (AKASI) score, and a hierarchical generalized linear model was used to evaluate the variation in AKASI scores, adjusting for sex, age, and skin phototype. A total of 270 subjects aged between 39 and 92 years were evaluated, with a majority having phototype I or II (77%), male gender (51%), a personal history of skin cancer (55%), and low adherence to sunscreen use (29%). The use of photosensitizing medications was reported by 61% of the sample. Through multivariate analysis, older age (βSE = 0.14; p < 0.01), lighter skin phototype (βSE = 0.15; p = 0.01), a personal history of skin cancer (βSE = 0.12; p < 0.01), sunburning (βSE = 0.12; p < 0.01), and the use of CCBs (βSE = 0.11; p = 0.02) were identified as independent risk factors for AK severity. However, regular use of sunscreen was associated with less severe AK (βSE=-0.10; p = 0.03). Photosensitizing drugs, including hydrochlorothiazide, were not identified as risk factors. Older age, lower skin phototype classifications, and a personal history of skin cancer were confirmed as severity risk factors for AK, while adherence to sun protection was identified as a protective factor. The use of CCBs was associated with more severe AK.
