People with at least three years of higher education are at greater risk for cancerous brain tumours than those with no more than nine years of schooling, perplexed researchers said Tuesday.
"There is a 19 per cent increased risk that university-educated men could be diagnosed with glioma," said Amal Khanolkar, a scientist at the Institute of Child Health in London and lead author of a study in the Journal of Epidemiology and Community.
For women, he said, the risk rose by 23 per cent.
"It was a surprising result which is difficult to explain," Khanolkar told AFP.
Concretely, the increase in risk is minimal because such brain tumours are rare.
At the lowest level of education, the chances of glioma were reported at five in 3,000. At the other end of the educational spectrum, the odds increased to six in 3,000.
But the question remained as to whether the gap — no matter how small — was real and, if so, what caused it.
Earlier research exploring a possible link between education or social level, on the one hand, and the frequency of brain tumours, on the other, had been inconclusive.
To "put to rest" these conflicting findings, Khanolkar and colleagues at the Karolinska Institute medical university in Stockholm used a new approach.
Rather than comparing a small number of brain tumour patients with healthy individuals, they sifted through the health records of 4.3 million adults tracked by the Swedish public health system from 1993 to 2011.
The researchers distinguished between three kinds of brain tumours — two of them non-cancerous — with different causes.
"At the lowest level of education, the chances of glioma were reported at five in 3,000. At the other end of the educational spectrum, the odds increased to six in 3,000."
The strong link between education level and tumour incidence held for all three types, but was strongest for deadly gliomas.
Interestingly, an even higher risk gap was found between low-income manual labourers and high-income men and women who did not work with their hands.
Gliomas are malignant brain tumours which grow rapidly and cause severe symptoms, including migraines, nausea and memory loss.
The survival rate is very low.
The study did not seek to explain the link between higher education and tumours, nor did it consider the potential impact of environmental and lifestyle factors, such as smoking or alcohol consumption.
The most common explanation for risk levels that rise with years spent in the classroom is that people with a higher education or income "have a better awareness of symptoms," Khanolkar said.
This would mean they are more likely to seek help and receive a correct diagnosis.
But while this may be true in a country with a health system that clearly favours the well-to-do, the argument is far less convincing in the Swedish context, the researchers said.
"Sweden has a universal, tax-based health care system," said Khanolkar. Everybody has roughly the same access to treatment.
"The symptoms are not avoidable — you can't sit at home and not seek care."
Moreover, he added, gliomas form very rapidly — often within 48 hours — and are excruciatingly painful.
"The symptoms are not avoidable — you can't sit at home and not seek care," he said.
To further their probe, the team will canvass an updated version of the database for possible correlations between ethnicity and brain tumour risk.
Underlying genetic variation in populations from different geographic regions — where certain mutations are more or less common — could be a factor, Khanolkar acknowledged.
One expert, commenting on the study, pointed to other possible culprits.
"Two additional factors which might be of interest in this context are height and, in women, hormone replacement therapy," said James Green, a clinical epidemiologist at the University of Oxford.
Risk of brain tumours — as of most cancers — is higher in taller people, and taller people tend to be richer and more educated," he noted.
"Hormone replacement therapy increases risk of brain tumours, and its use tends to vary by socio-economic group."
Your Essential Sunscreen (and Skin Cancer Prevention) Guide
Choosing the Right Formula(01 of04)
Open Image ModalSunscreens come in two forms: Physical sunscreens, such as zinc oxide and titanium dioxide, are minerals that sit on the skin's surface and reflect the sun's rays like tiny mirrors. Chemical sunscreens, such as avobenzone and oxybenzone, work like little sponges to absorb and neutralize solar energy. Physical blockers can deflect both types of rays: UVA and UVB. Chemical ingredients may defend against only one or the other. Look for broad spectrum on the label to make sure the product you use covers both.
There are pros and cons with each form. While physical blockers very rarely cause an allergic reaction, a small percentage of the population is allergic to avobenzone or oxybenzone, according to Darrell Rigel, MD, clinical professor of dermatology at New York University Langone Medical Center. "The main problem with physical sunscreens is that they tend to be less water-resistant," Rigel says. "You put them on and go in the pool or sweat, and they can just run off." If you're the sporty type, select a chemical sunscreen, which is more likely formulated to resist water and perspiration. No matter what kind you end up choosing, "you need at least an SPF 30 every day," says Rigel.
Making Sure Your Sunscreen Works
If dermatologists could tell you one thing about the way you apply sunscreen, it's this: You're skimping. To shield your face and body adequately when you're outdoors, experts say you need a full ounce of sunscreen (equivalent to a shot glass). And you need to reapply that amount every two hours -- more often if you're getting wet. (Water-resistant sunscreens are rated for 40 or 80 minutes -- check the label. After that, it's time for another coat.) So even if you're spending only a long weekend in Bermuda, a couple of TSA-approved bottles won't cut it. When your day is spent mostly indoors, it's OK to say "one (coat) and done." "You still need an SPF 30, but you can put it on in the morning and not reapply unless you go out for errands," says Rigel. (credit:Sabine Villard/Trunk Archive)
Stop! Now Read This(02 of04)
Open Image ModalIf you've got skin, the following applies to you.
There are two types of skin cancer. Nonmelanoma -- basal cell or squamous cell carcinoma -- usually looks like a little pimple or sore, may also bleed and doesn't go away after a few weeks. "Anything that's bleeding, scabbing, crusting and not healing needs to be checked by a dermatologist," says Lisa Chipps, MD, assistant clinical professor of dermatology at Harbor-UCLA Medical Center. Melanoma is a potentially deadly form that often shows up as an irregular mole. Follow the ABCDE guide. If your spot fits any of the descriptions below, get yourself to a dermatologist, stat.
Asymmetry: one side is different from the other
Borders: scalloped or irregular edges
Color: multiple shades instead of a uniform brown hue
Diameter: larger than a pencil eraser
Evolving: anything that changes in size, shape or color over time
Special Alert
Attention, darker-skinned women: You are more susceptible to a specific form of melanoma that tends to develop on palms and soles, says Carlos Charles, MD, clinical instructor of dermatology at Weill Cornell Medical College. It may also appear as a linear pigmented band on the nail bed, so check those areas regularly. (credit:Gillian MacLeod)
The Best Defense(03 of04)
Open Image ModalInquiring Minds Want to Know...(04 of04)
Open Image ModalWhat's the best sunscreen?
"The one you'll wear every day -- as long as it's broad spectrum and at least SPF 30," says Chipps. "You have to like the texture, or you aren't going to use it. It's a personal preference, and finding yours may take some trial and error."
Won't sunscreen make my oily skin break out?
It's not the sunscreen agents causing your pimples; it's the formula, says Rigel. If blocked pores are a problem, look for OIL-FREE or NONCOMEDOGENIC on the label.
Is the SPF in my makeup enough?
That would be a resounding no, say dermatologists. "If you wear a thick coat of foundation all over your face, then maybe," says Chipps. "But most people don't -- they apply a thin layer and put on only a little extra if they're covering a blemish." If you want to thwart the rays, first smooth on a lightweight sunscreen, then put on your makeup. (credit:Ridofranz/iStock/Thinkstock)