Comparison of Sun Protection Factor (SPF) 30 Persistence Between Inorganic and Organic Sunscreen in Swimmers: Protocol for a Multicenter, Randomized, Noninferiority, Split-Body, Double-Blind Clinical Trial.

Background: Outdoor swimming athletes are often exposed to undesirable environmental conditions such as long-term sun exposure. The risk of sunburn can still occur in this population due to the loss of sunscreen and an increase in the sensitivity of the skin to ultraviolet rays, particularly ultraviolet B, in wet conditions. Some previous trials showed that organic sunscreens had a longer shelf-life than inorganic sunscreens after exercise due to their characteristics to bind better with the skin layer. Meanwhile, inorganic sunscreens tend to form layers on the skin's surface so that they can be more easily removed. To our knowledge, no studies evaluate sunscreens' resistance, either inorganic or organic, after exercising in Indonesia.

Objective: This study aims to evaluate the persistence of inorganic versus organic sunscreens used by swimmers. The primary objective is to assess whether the inorganic sunscreen is as good as the organic sunscreen in the field of the persistence of sunscreens after swimming for 1.5 hours.

Methods: This study is a randomized, split-body, double-blind, noninferiority, and multicenter clinical trial in Cikini, Jakarta, Indonesia. An estimated 22 athletes in each group, who aged 18-40 years and practice in the morning or afternoon, will be randomized using a computer-generated randomization method. We calculated the sample size using the difference in the average decrease in sun protection factor (SPF) levels that is considered significant based on the clinical judgment set by the researchers, which was 5. Neither the research subjects nor the researchers are aware of the type of sunscreen that will be applied. The hypothesis will be tested using paired-sample t test or Wilcoxon to assess the difference of SPF levels in each group between organic and inorganic sunscreens with SPSS (version 20.0; IBM Corp).

Results: This study has been approved by the Ethical Committee Faculty of Medicine Universitas Indonesia and is funded by the International Publication Grant from Universitas Indonesia. The enrollment process was completed in December 2020.

Conclusions: This study will test all procedures in preparation for conducting the main study, including several potential obstacles and challenges from the perspective of participating physicians and eligible swimmers. The study results will be disseminated through publications in a peer-reviewed journal with Open Access format. This study will provide information about SPF 30 persistence in sunscreens and the best type of sunscreen to be used while swimming, particularly for athletes.

Trial Registration: ClinicalTrials.gov NCT04618536; https://clinicaltrials.gov/ct2/show/NCT04618536?term=NCT04618536.

International Registered Report Identifier (irrid): RR1-10.2196/42504.