Ultraviolet radiation (UVR) is the most important risk factor for skin cancer. Indoor tanning, defined as the use of an ultraviolet emission device to produce a cosmetic tan[1], has been associated with increased risk of melanoma and non-melanoma skin cancer (NMSC), and thus has been classified as a group I carcinogen by the International Agency for Research on Cancer[2]. Despite the risk posed by this activity, indoor tanning is common practice among young people in developed countries. A systematic review and meta-analysis of 12 studies of indoor tanning and NMSC showed that ever exposure to indoor tanning was associated with a higher risk of both, squamous cell carcinoma and basal cell carcinoma, and that exposure at a young age (< 25 years of age) increased these risks considerably[1]. Similarly, melanoma risk was significantly higher due to sunbed use, as reported by a systematic review and meta-analysis of 27 observational studies[3]. Since indoor tanning is a potentially modifiable exposure it is of interest to examine its frequency and the characteristics of its users in the ALSPAC cohort. Up until 2017 ALSPAC did not include questions regarding indoor tanning. The exceptions are the mother’s ‘Your environment’ questionnaire administered in early gestation asking how often they had used a sun bed or lamp during their pregnancy, and the child-based KN questionnaire at 69 months old asking about ever use of sun bed or lamp and its frequency. On the other hand, ALSPAC children have been assessed with respect to natural sunlight exposure at regular intervals, although only up to the age of 12 years.
In one of the last waves of data collection for ALSPAC Young People (YP, Life@25+) we requested that a number of questions regarding indoor and outdoor tanning be included. This information is now available and we would like to investigate the determinants and the effects of tanning behaviour in the participants of ALSPAC at different life stages.

References
1. Wehner, M. R.; Shive, M. L.; Chren, M.-M.; Han, J.; Qureshi, A. A.; Linos, E. Indoor tanning and non-melanoma skin cancer: systematic review and meta-analysis. Br. Med. J. 2012, 345, 1–9, doi:10.1136/bmj.e5909.
2. El Ghissassi, F.; Baan, R.; Straif, K.; Grosse, Y.; Secretan, B.; Bouvard, V.; Benbrahim-Tallaa, L.; Guha, N.; Freeman, C.; Galichet, L.; Cogliano, V.; WHO International Agency for Research on Cancer Monograph Working Group A review of human carcinogens--part D: radiation. Lancet. Oncol. 2009, 10, 751–2.
3. Boniol, M.; Autier, P.; Boyle, P.; Gandini, S. Cutaneous melanoma attributable to sunbed use: systematic review and meta-analysis. BMJ 2012, 345, e4757–e4757, doi:10.1136/bmj.e4757.