Sunscreen Revisited – Should You Act on New Evidence?

Back in 2011, I wrote a post on sunscreen, questioning the rational behind it’s use.

Since writing that piece, a new randomly controlled trial has been conducted on sunscreen use and melanoma risk, and just recently, the official health advice on sun exposure has been changed in UK, so I thought it was about time for an update.

Sunscreen Use and Melanoma Risk: New RCT

When I wrote my original article on suncreen use, there were no RCTs available – all of the evidence was based on epidemiological studies.

None of these studies indicated strong evidence that sunscreen use was effective at preventing melanoma, and some even showed that sunscreen use may even increase melanoma risk!

It just recently came to my attention, however, that later that same year (2011), an RCT on sunscreen use and melanoma risk was conducted in Australia by Adèle C. Green et al:

Reduced Melanoma After Regular Sunscreen Use: Randomized Trial Follow-Up

As the title may suggest, the conclusion of the authors of the study was that using sunscreen was indeed protective against melanoma.

In my original post, based on the evidence available up to that point, I questioned the use of sunscreen, and personally did not use it, preferring to get sufficient sun to tan and produce vitamin D, and then seeking shade and using clothing to avoid overly tanning or burning.

So you may ask, has my perspective changed in the light of new evidence?

Analysing the Study

The study tracked just over 1600 participants for 10 years. Half of the participants were assigned to a group who had to apply sunscreen thoroughly on a daily basis (in addition to questioning their use, the scientists also collected their empty bottles to ensure compliance). The remaining half were left to their own devices.

After 10 years, 11 primary melanomas had been identified in members of the daily sunscreen group, and 22 in the discretionary group – exactly double. From this seemingly startling difference, the scientists conducting the study concluded that sunscreen use is an effective method of preventing melanoma.

Based on this evidence, will I be running out and buying stockpiles of sun cream?

Not quite yet. My reasons for hesitation are:

• This is just one, relatively small study

The results of the study barely reached statistical significance. Though the number of cases in the discretionary group is double that of the daily group, one must bare in mind that the number of cases was a tiny fraction of the total sample size. 33 cases out of 1600 participants is just 2%.

That the results just barely reached statistical significance means that the results are very probably due to the sunscreen use, but it is not impossible that it was just due to freak chance.

Were there prior evidence from the epidemiological studies as to the efficacy of sunscreen, and perhaps another RCT of a similar or larger size, also with positive results, we could take all these together as firm confirmation.

For me however, one small study which barely reaches statistical significance is a little too early to draw firm conclusions.

• There was no placebo arm

One of the biggest confounding factors in this study, in my opinion, is that there was no placebo sunscreen. I appreciate that this was done for ethical reasons. Had you given people fake sunscreen, and then they’d developed fatal skin cancer, that would be a bit awkward. This however leads to one group who are left to their own devices, and another group who are constantly reminded about melanoma risk.

How do we know that the reduced melanoma cases in the daily application group were actually down to the sunscreen, or if they were simply more mindful not to get burnt than the discretionary group? Which leads me onto my next criticism…

• Sunscreen is not the only fruit

I’ve talked about this common issue with “the gold standard of science” the RCT before, in relation to diets and supplements.

A very well designed RCT can tell you which is better, option A or B (or C or D etc depending how many arms the study has).

In this study, the scientists compared A: Daily sunscreen application, to B: Doing nothing.

How about option C: Getting reasonable sun exposure, without overly tanning or burning by covering up with clothing and seeking shade?

• Melanoma is not the only disease

Following on from the above, another common problem with RCTs is that they only tell you what effects the variables being tested (A or B) have on the outcomes being measured (X, or Y, Z etc depending how many variables are measured).

In this study, there is just one outcome measured – incidences of melanoma. While melanomas are certainly not pleasant, and can potentially be fatal if undetected/untreated, studies such as this which just focus on one outcome, have the potential to miss the woods for the trees.

It is my opinion that studies such as these should be looking for all cause mortality (which in fact it did, with 87 deaths in the intervention arm, and 86 in the control), tracking any/all diseases, and measuring general well-being. Again, I appreciate scientists are limited by time and budget, but this information is important.

Sunscreen use has been linked to rises in numerous other cancers, with possible mechanisms such as blocking vitamin D production, increasing time in the sun without burning, and/or chemicals leaching through the skin.

Potentially reducing your melanoma risk from 2/80 to 1/80 is all very well and good, but not if it simultaneously raises your risk of another cancer or disease, particularly as melanoma is relatively easy to detect and treat in comparison to others.

Living with bears, for example, is one way to reduce your risk of dying from a heart attack, but is not an option I would personally go for.

• The study is funded by L’Oreal

It has been shown that the source of funding for a study can strongly bias the result. I.e. a study funded by the manufacturer of a product, is much more likely to show the product as effective than an independently funded study.

Aside from the criticisms above, the study does appear to be fairly rigorous, and I am by no means suggesting any kind of corruption or collusion from the authors of the study. However, who is to say that other similar studies haven’t been funded by sunscreen manufacturers in the past, which failed to show a significant protective effect, and then never saw the light of day?

This is a common tactic used by drug companies, as highlighted in Ben Goldacre’s book Bad Pharma. Roll the dice enough times, and eventually you’ll get double 6.

Now, perhaps I’m getting into tinfoil hat wearing paranoia territory here, but it is food for thought. I appreciate that studies such as these are very expensive to conduct, which could explain why we still only have 1 small RCT to inform our decisions, but when you consider that the sunscreen industry’s estimated value is around $1.3 billion, one would think they could afford to fund a few more (statistically significant?) studies?

The Study I’d Like to See

If I had unlimited resources, I’d like to see a study with at least 12,000 people. Let’s assign 4000 to 1 of three groups. 1 using sunscreen daily, 1 educated to get enough time in the sun to get a mild tan, but to avoid getting overly tanned or burnt by seeking shade and using hats and clothing, plus a control group who can do whatever they like.

Let’s then track them for all cancers and disease, plus measure well-being for good measure.

Of course, this probably isn’t going to happen. We are already buying lots of sunscreen, so I guess the sunscreen manufacturers have nothing to gain and everything to lose from sponsoring such a study. Unless perhaps we can get money from “Big Hat”…?

Revised Sun Exposure Advice from NICE in the UK

So unfortunately, the new study hasn’t really shed any new light on the matter. What is good to see, however, is that the official message with regards to sun exposure (in the UK at least), is changing for the better.

Here is the latest message from NICE:

Weighing the benefits and risks of sunlight exposure

In summary, the new guidelines make a point of raising awareness that some sun exposure is good, and that people should make an effort to get some unprotected exposure to at least the forearms and hands, particularly at risk groups such as older people, indoor workers, or darker skinned people living at more northern latitudes.

With regards to the potential dangers, they highlight that sunscreen alone is not adequate protection, rather they should seek shade and cover up with clothing and hats to avoid over exposure. All pretty good advice if you ask me!

My thoughts on sunscreen and sun exposure as of 2015

My general thoughts haven’t changed drastically, but here’s where I’m up to now:

• Get outside and get some sun

The benefits of being out in the sun (even if it’s weak northern sun), can’t be substituted by some UV tubes or a bottle of Vitamin D pills, particularly if that time in the sun is spent moving, playing and having fun, especially with friends. Get sufficient unprotected exposure to bronze a little, without turning a strange colour.

• Don’t get burnt

I’d say the jury is still out as to whether sun burn causes melanoma. It does cause other types of skin cancers and skin damage however, which while not necessarily fatal, are still unpleasant. It’s also painful, and makes you look like a bit of an idiot.

Personally, where possible I’d do this by covering up with clothing, and/or seeking shade. You are a human being, not a potato, you don’t have to roast yourself at high temperature for 4 hours every day to get a nice tan.

• Perhaps judicious sunscreen use can have its place?

While I am certainly not convinced we should be liberally applying sunscreen on a daily basis in order to try and prevent melanoma, one thing it most certainly does, is stop you from getting burnt.

Though my preferred method for this would be a combination of gradually building up a tan by incrementally increasing sun exposure using shade and clothing, I appreciate that this is not always possible.

Say for example you are an endurance athlete who lives in Northern Europe, who is taking part in a race just south of the equator in January. It’s going to be hot. Your skin is not conditioned for it and will burn if exposed. It’s not going to be practical to run an endurance race in the heat, fully clothed with a large brimmed hat. In this instance, sunscreen would probably be a good idea.

Where I’m still undecided, is for pale skinned active outdoor lovers who live in hotter climes than those in which their ancestors evolved (i.e. pale skinned people of Northern European origins living further South.

If there are risks to sunscreen use, I think these most likely come from:

1. Blocking all vitamin D production from never getting exposure without cream
2. Encouraging people to spend too much time out in the sun without shade or clothing protection.

1 is easily remedied – just get some exposure without cream.

2 is easily remedied for sun bathers – just lie in direct sun for a shorter period of time so you don’t burn, then go under a sun shade. You can more easily read a good book then too, double win.

But what if you regularly play beach volley ball tournaments, or love spending the whole day surfing or running the trails in the blazing sun?

Yes, in theory you could do these activities in wetsuits or base layers, but that would rather take away much of the enjoyment.

In these cases, the length of time out in direct sun is dictated by the activity, irrespective of whether sunscreen is used or not – could there be a potential benefit?

The answer is, unfortunately, that we really don’t know, and as always, more research is needed.

I for one would certainly sign up for the trial…