Randomised, in people, over four and a half years, measured on skin rather than in a survey. It holds.
Prevents premature ageing. Daily use protects against fine lines, wrinkles and loss of firmness caused by the sun.
The market's own words. No brand is named, because the claim is the thing under examination and it belongs to dozens of them.
In adults under 55 in a high-UV climate, does applying broad-spectrum sunscreen daily, compared with using it at your own discretion, reduce measured skin ageing over several years?
The same claim written as a proposition somebody could go and check: who, compared with what, measured how, over how long.
Hughes, Williams, Baker and Green, in the Annals of Internal Medicine in June 2013. Nine hundred and three adults under 55 in Nambour, subtropical Queensland, randomised either to apply broad-spectrum SPF 15 to head, neck, arms and hands every morning, or to carry on using sunscreen however they liked. Four and a half years. The endpoint was not a questionnaire and not a photograph: silicone replicas were taken from the back of the left hand and graded for microtopography, so the measurement did not know which group it came from. Skin ageing increased 24 per cent less in the daily group (relative odds 0.76, 95 per cent CI 0.59 to 0.98). The unflattering parts, stated plainly: SPF 15, which is below what most people now buy; the back of a hand, not a face; a latitude that delivers far more UV than most of Europe; and the sunscreen was supplied by a manufacturer, though the study itself was funded by the National Health and Medical Research Council of Australia rather than by industry. It is still, more than a decade on, the only trial of its kind — nobody has repeated it, and nobody is likely to, because randomising people away from sunscreen for five years is no longer something an ethics committee will approve.
Very little, honestly, and that is the point of the position. What would narrow it is evidence that the effect does not carry across skin tones, since the trial population was overwhelmingly fair-skinned and the mechanism is not identical in richly pigmented skin. What would sharpen it is a trial with a facial endpoint and a modern SPF, which would tell us the size of the effect people are actually buying rather than the size measured on a hand at SPF 15.
It does not mean a particular bottle has been tested — nothing here is a verdict on a brand, and a 60-pound serum with SPF in it is not better supported than a 9-pound one at the same protection. It does not mean sunscreen reverses anything: the trial measured ageing that did not happen, not ageing that went away. It does not mean 24 per cent off your face, on your continent, at your SPF. And it does not mean the rest of the aisle inherits this — the evidence belongs to sun protection, not to whatever else is in the formula.
You are paying for sun protection, and the anti-ageing claim is the one place in this Register where the label and the literature are pointing at the same thing. What you are not paying for is the difference between one broad-spectrum sunscreen and another at the same SPF: the trial supports the habit, not the price. Buy the one you will actually put on every morning, which in practice means the one whose texture you do not resent, and spend the difference somewhere the evidence is thinner and needs the help.
Type and funding are stated because they change what a study is allowed to prove, and because a trial paid for by the company selling the thing is not disqualified — it is just not the same evidence as one that was not.