Cohort profile: The Cancer Risk Associated with the Body Art of Tattooing (CRABAT) study

Tattooing, involving the injection of pigments into the skin, has become increasingly popular, with up to 40% of individuals under 40 years old tattooed in high-income countries. Despite regulatory measures, tattoo inks may contain hazardous substances such as polycyclic aromatic hydrocarbons, primary aromatic amines, and metallic impurities, many of which are classified as carcinogens. Research on systemic health risks, particularly cancer, associated with intradermal ink exposure remains limited. Complications like contact allergies and inflammatory skin reactions are more frequently reported among tattooed individuals. However, cancer risks from tattooing, especially for internal cancers like lymphoma, are challenging to assess. Existing case-control studies indicate mixed findings regarding hematologic cancers, with one large study reporting a 20% increased lymphoma risk among tattooed individuals in the first two years post-tattooing. Here, we present the Cancer Risk Associated with the Body Art of Tattooing (CRABAT) study, that is, to our knowledge, the first larger study that prospectively investigates tattoo-related cancer risks. CRABAT follows up over 110,000 participants for long-term health effects within the French Constances cohort with objective cancer data linkage. Of [~]13,000 participants that were tattooed in 2020, detailed tattoo exposure assessment via a validated tattoo exposure questionnaire was conducted in 2023 (response rate >60%). With its robust dataset through linkage to the Constances variable pool, CRABAT enables the analysis of exposure-response relationships, and addresses potential confounders such as sociodemographic and lifestyle factors, and alternative pathways such as tattoo-related infections. Body word count: 2498 words