International health agencies recommend that no sun protection is necessary when the UV index is under 3. However, new data from a New Zealand NIWA research group published last month (www.nature.com/scientific reports) raised significant questions about the validity of this advice.
The issue is that the UV index value of 3 was chosen as the level of UV intensity which will lead a fair skin person to burn after one hour of exposure. This assumes no one spends more than one hour at a time outside, which is clearly flawed. Their data suggests that similar skin damage can be done from a long exposure at low UV dose, as is seen in short exposure at a higher UV dose.
This sits somewhat contrary to data about the body's ability to adapt to low dose sun exposure reported in this blog on 4 February 2017 below. The current study quotes recent evidence that there is a measurable increase in DNA damage from small increases in UV exposure even at low level. The February report however looked at a reduction in DNA damage with time, suggesting the body can adapt over a period of weeks if the exposure levels are low. The beauties and controversies of medical science!
They do raise another interesting observation. In winter, UV exposure to the face and neck is higher than the UV index would suggest. This is a result of the sun sitting lower in the sky, and therefore more dose hits these vertical surfaces than it does the horizontal surface that is used to measure the UV index.
A recent study published in the medical journal, Dermatologic Surgery investigated patient preference in the treatment of the most common type of skin cancer, basal cell carcinoma. They reviewed six studies on the subject.
In four of the six studies, recurrence of the tumour was rated the most important attribute. Cosmetic appearance of the area after treatment was rated most important in one study, and the second most important in three studies.
This information is not surprising but highlights the utility of Mohs micrographic surgery for appropriately selected skin cancer lesions. Mohs surgery offers the lowest recurrence rates for these cancers and because it also specifically allows for the sparing of normal surrounding tissue, the defect size and subsequent reconstruction/scar can be minimised for the best cosmetic result. Additionally, recurrent tumours will require further surgery at a later date resulting in a larger defect and reconstruction. Also, recurrent tumours are more difficult to clear, have lower cure rates, and are more technically difficult to reconstruct.
Therefore, the first chance to treat is always the best chance to minimise the recurrence rate, and maximise the cosmetic outcome.
With skin cancer being such a major health issue in New Zealand it is always pleasant to read people are working on ways to improve challenges in the diagnosis of this disease.
In a recently published paper in the journal Skin Research and Technology, Magalhaes and colleagues reviewed the literature to date on the use of infrared thermal imaging for the diagnosis of skin cancer. This picks up subtle differences in temperature between benign and malignant skin lesions, presumably based on increased blood flow in the malignant lesions.
This non-invasive technology may be a promising tool for the identification of early skin cancer, hopefully in the not-too-distant future.
We have always been led to believe the UV radiation reflected off the water and sand when at the beach, or out on the water is part of the reason we are more prone to sunburn when undertaking these activities.
Interestingly, a recent study in the medical journal Photodermatology Photoimmunology Photomedicine (March 2018) concluded that in fact the vast majority of the sun's UV radiation passes into the water, and very little is reflected especially when the sun is high in the sky (the time when the UV level peaks). We certainly notice the reflected light with our eyes, but the reflected UV does not appear to have a major bearing on our skin.
The corollary of this fact is of course that we are still exposed to almost the same UV when we are swimming under the water as when sitting on the beach. The UV index was only reduced to half by a depth of two meters under the surface.
Adequate shade and protection from the sun above remains the priority when enjoying the beach or water sports.
Self skin examination is very useful for detecting melanoma. In 1985, the ABCD acronym was introduced to help people identify suspicious moles themselves.
A = Asymmetry
B = Border irregularity
C = Colour irregularity
D = Diameter > 6mm
The E was a later but very important addition.
E = Evolving (changing)
Since that time, many of us have changed the D from diameter to DIFFERENT (i.e an 'ugly-duckling' mole that looks different for any of your other moles).
A late 2017 study reported in the Journal of the American Academy of Dermatology tested the utility of just the Ugly Duckling sign versus the ABCD acronym for simulated moles in 101 adult volunteers. The ugly duckling sign demonstrated superior accuracy of melanoma recognition, and better specificity than the ABCD group.
This is a simulated study in a relatively small number of participants, but it underlines the usefulness of a very simple tool that may increase the pick-up of melanoma by all of us. We tend to teach the whole ABCDE (with D as different) but given this data, possibly using just the D on its own is easier and more effective.
A lot has been written lately about sunscreens in the medical literature and the press. One comment you will read frequently is that there is very little benefit to an SPF (Sun protection factor) higher than SPF30. The basis behind this advice is scientifically sound.
Approximate UVB ray blockade:
SPF15 sunscreens block 93%
SPF30 sunscreens block 97%
SPF50 sunscreens block 98%
Looking at these figures, it would certainly seem reasonable to conclude, increasing SPF above 30 provides very little additional benefit.
However, standard SPF laboratory testing that dictates a sunscreens SPF rating is very different from how sunscreens are used in real life. Multiple studies have confirmed the fact that we do not apply our sunscreen anywhere near as thick as in the standardised SPF testing protocol (2 mg/cm2). When we apply our sunscreen at the beach, we are likely to be getting considerably less protection than the product provided in the laboratory setting. Therefore, using a higher SPF rated product will help cover the difference between testing and real-life usage.
This has now been proven in a December 2017 study published in the Journal of the American Academy of Dermatology. Nearly 200 people were randomised to apply a SPF50 sunscreen to one side of their face, and a SPF100 sunscreen to the opposite side of their face without knowing which was which. No advice was given as to the amount, or how to apply the sunscreen, so the experiment was closer to representing real-life usage. Independent and the subjects' own assessment of sunburn scores following sun exposure both showed significantly higher sunburn on the SPF50 side of the face compared to the SPF100 side.
There is also a second reason why a higher SPF sunscreen is likely to be more desirable. Broad-spectrum sunscreens (which are universally recommended as the best) can only be labelled 'broad-spectrum' when their UVA protection is at least 30% of the UVB protection (the SPF rating is based on UVB testing alone). UVA is a longer wavelength radiation present in the sun which has been implicated in both skin cancer and sun-damage to the skin. A higher SPF sunscreen therefore offers a higher UVA protection and therefore better broad-spectrum protection.
Sunscreens are only filters and do not block all of the sun's harmful radiation. They should be used in conjunction with other sun-protection behaviours such as seeking shade, using clothing and sunglasses, and keeping out of the sun in the middle of the day when the UV levels are at their highest. However, it seems higher SPF rated sunscreens do indeed offer increased protection when used in real life.