Sun Protection

Research summary

• Sunscreen's evidence for preventing skin cancer is a genuine study in how observational and randomized evidence can tell different stories.
• A meta-analysis of 29 studies covering 313,717 people -- mostly case-control designs -- found no significant overall association between sunscreen use and skin cancer risk (odds ratio 1.08) for either melanoma or non-melanoma skin cancer, and noted that a positive association seen in older studies has steadily weakened since the 1980s, likely reflecting confounding by indication (people already at higher risk tend to use more sunscreen).
• The one long-running randomized controlled trial on the question tells a different story: the Nambour trial in Queensland, Australia randomly assigned 1,621 adults to daily versus discretionary sunscreen use for 4.5 years, and found no effect on basal-cell carcinoma but a significant reduction in the number of squamous-cell carcinoma tumors (rate ratio 0.61) in the daily-sunscreen group.
• Ten years after the trial ended, a follow-up found the daily-sunscreen group had less than half as many new melanomas as the discretionary group (11 versus 22 cases), with the reduction concentrated in invasive melanoma (hazard ratio 0.27).
• Because this level of evidence comes from a single trial population in a very high-UV environment, and the broader observational literature remains null, the case for sunscreen rests unusually heavily on one well-conducted but singular randomized trial rather than a consistent body of evidence.