On 4 June 2013, the Annals of Internal Medicine published a randomised trial with a clear message for anyone who skips sunscreen on ordinary days. Adults who used it daily showed less skin ageing than those who applied it only when they felt like it. The difference was 24 per cent over 4.5 years.
The research came from Nambour, a community in Queensland, Australia, at a latitude of 26 degrees south. It analysed 903 adults younger than 55, drawn from 1,621 people randomly selected from a community register. The paper is titled “Sunscreen and Prevention of Skin Aging: A Randomised Trial”, and its authors are Maria Celia B. Hughes, Gail M. Williams, Peter Baker and Adèle C. Green.
How the trial worked
The work was part of the Nambour Skin Cancer Prevention Trial. According to Ob.Gyn. News, that trial studied 1,621 adults from 1992 to 1996. It originally tested whether sunscreen or dietary supplements affected skin cancer risk, photoaging and actinic keratosis.
For the ageing analysis, participants were randomly placed into four groups. Two groups used broad-spectrum sunscreen daily, and two used it at their own discretion. Each of those pairs was further split, with half taking 30 mg of beta-carotene and half taking a placebo.
The researchers focused on adults under 55. This was done to exclude the effects of growing old on participants’ skin.
The daily group was told to apply an SPF 15+ product to the face, neck, arms and hands every morning. They were also told to reapply after sweating, swimming or a few hours outdoors. Sunscreen bottles were weighed to check how much people were really using.
Skin ageing was measured through silicone impressions of the skin surface, called microtopography. These were taken in 1992 and again in 1996, from the backs of the hands. Assessors graded them without knowing which group each person belonged to.
What the results showed
The daily sunscreen group showed no detectable increase in skin ageing after 4.5 years. From the start of the trial to the end, ageing was 24 per cent lower in this group than in the discretionary group. The relative odds were 0.76, with a 95 per cent confidence interval of 0.59 to 0.98.
Beta-carotene supplements made no overall difference to skin ageing. The authors said further study was needed to rule out either a benefit or a harm.
The authors concluded that regular sunscreen use slows skin ageing in healthy, middle-aged men and women. They also listed limitations: some outcome data were missing, and the trial had only modest power to detect moderate effects. The National Health and Medical Research Council of Australia was the main funder.
Why it mattered
Sunscreen had long been recommended for preventing skin ageing. Yet the authors noted that supporting evidence was lacking. Many reasons existed to expect a benefit, but this trial put the idea to a controlled test. Thirteen years on, it is still the study most often cited for the claim.
FAQ
Did the study use a high-SPF sunscreen?
The daily group was told to use a broad-spectrum product of SPF 15 or above. The trial did not compare different strengths.
Did the study test the face?
Participants applied sunscreen to the face, neck, arms and hands. The skin impressions used to measure ageing were taken from the backs of the hands.