Sunscreen and Ageing Skin: What a 4.5 Year Trial Found

Sunscreen does not stop skin from ageing. It is not a filter for time. What the best trial we found does show is narrower and easier to believe: people who wore it every day showed less change in their skin's surface than people who wore it when they felt like it.

This piece goes through that trial, what the American Academy of Dermatology and Cleveland Clinic say about how sun changes skin, and what daily sunscreen cannot do.

What is actually going on when sun changes skin?

Cleveland Clinic calls it photoaging: the premature ageing of skin from ongoing exposure to ultraviolet A (UVA) and ultraviolet B (UVB) radiation. UVA reaches the deeper layer of skin, the dermis, which holds the collagen and elastin that give skin its tightness and bounce. UVB acts on the outer layer.

The signs Cleveland Clinic lists are the ones people usually blame on age alone: more lines around the eyes and mouth, loss of tone and elasticity, freckles and age spots, uneven colour and texture, and thinner skin. Some of that is time. A share of it is sun, and the sun part is the part you can plan around.

What does the evidence say?

The study most people point to was published in the Annals of Internal Medicine in 2013 by Hughes and colleagues. It ran in Nambour, Australia, and it was a randomised, controlled trial, which means chance decided who got what.

• Who: 903 adults under 55, drawn from 1,621 people randomly selected from a community register.
• What: Four groups. Half were told to use broad-spectrum sunscreen daily. The other half used it at their own discretion, as they normally would. Each of those halves was also split, so some took 30 mg of beta-carotene and some took a placebo.
• How long: 4.5 years.
• How it was measured: the change in the skin's surface texture (microtopography) between 1992 and 1996, graded by assessors who did not know which group anyone was in.

The daily sunscreen group showed no detectable increase in skin ageing over the 4.5 years. Compared with the discretionary group, their skin ageing was 24% less (relative odds 0.76, 95% confidence interval 0.59 to 0.98). Beta-carotene supplements made no overall difference.

What sunscreen cannot do

This section matters as much as the last one.

• It does not undo what has happened. Cleveland Clinic is direct that once UV radiation changes the DNA in skin cells, that damage cannot be undone. It adds that this does not mean the appearance of your skin cannot change.
• It is not enough alone. The AAD says sunscreen alone cannot fully protect you, and recommends shade, protective clothing, hats and UV-blocking sunglasses alongside it.
• The trial has limits. The authors note that some outcome data were missing and that the study had modest power to detect moderate effects. It was one place, with adults under 55, and it looked at skin texture rather than every sign of ageing.
• It is not a timeline. Nothing here tells you how your own skin will look in any given year.

What to do about it

The AAD guidance is plain and practical:

• Choose a sunscreen with SPF 30 or higher that is broad-spectrum (covers UVA and UVB) and water resistant.
• Use about 1 ounce, roughly a shot glass, to cover skin that clothing does not. For the face, use at least 1 teaspoon, about the length of your index and middle fingers.
• Put it on before you go outside. The AAD says it takes about 15 minutes for skin to absorb it and protect you.
• Reapply about every two hours, and right after swimming or sweating.

Cleveland Clinic suggests avoiding peak UV hours, which it puts at roughly 10 a.m. to 4 p.m. The AAD's shade advice names 10 a.m. to 2 p.m. The two differ, so count the middle of the day as the time to look for shade.

Where copper peptides fit, and where they do not

Copper peptides are not a sunscreen, and no study we have read tests them as a substitute for one. If you use a copper peptide serum, the sunscreen still goes on top in the morning. If you are wondering how the two sit together, our piece on copper peptides and sun sensitivity covers it.

No paper has tested a koppā formula. What we can say is that a daily serum such as our 2% GHK-Cu serum belongs in the part of your routine that sits under SPF, not in place of it.

If your interest is in why the skin around the eyes and forehead lines early, see what causes crow's feet and why forehead wrinkles show up young.

Who to talk to

A dermatologist is the person for a new or changing mole or spot, and Cleveland Clinic says the same. They are also the right call if you have had a lot of sun over the years and want to know what can change how your skin looks. Cleveland Clinic lists retinoids, laser resurfacing, chemical peels and fillers among what dermatologists offer.

Frequently asked questions

Do I need sunscreen on cloudy days?

We did not find a source that answers this for cloudy days specifically, so we will not guess. The AAD advice is to apply sunscreen every day on skin not covered by clothing if you will be outside.

Is SPF 30 enough?

Both the AAD and Cleveland Clinic give SPF 30 or higher as the standard, with broad-spectrum cover.

How much should I put on my face?

At least 1 teaspoon, according to the AAD, about the length of your index and middle fingers.

Can I skip sunscreen if I wear a hat?

Hats help. The AAD lists them next to shade, clothing and sunglasses as part of the picture, and says sunscreen alone is not full protection. The same goes the other way: a hat does not cover every exposed area.

Does a vitamin like beta-carotene do the same job?

In the Nambour trial it did not. Beta-carotene had no overall effect on skin ageing, and the authors say more study is needed before ruling out either benefit or harm.

Is any of this a promise about how my skin will look?

No. The trial measured groups of people, not individuals, and skin ageing has causes beyond the sun.