Study shows: Europeans clearly overestimate the benefits of cancer screenings

Interviews with more than 10,000 individuals from 9 European countries comprised part of the first European-wide study on the understanding of early detection screening for cancer carried out by the Harding Center for Risk Literacy in cooperation with the Association for Consumer Research (GfK), Nuremberg. The findings are surprising: It turns out that Europeans are poorly informed optimists when it comes to early detection screening.

In discussions about the fundamentals of modern public health systems, one ideal is evoked time and again: that of the responsible, well-informed patient. Are citizens in Europe truly well enough informed to make a competent decision? As far as their knowledge about the benefit of early detection screening for cancer is concerned, the answer is a clear "no".
The researchers discovered that 92 % of all interviewed women overestimate (or do not know) the benefit of mammography as a means to prevent fatal breast cancer. And 89 % of all men expect too much of the PSA test with respect to reducing the risk of fatal prostate cancer or admit that they do not know enough about this topic.

Just how useful is mammography? Earlier studies showed that of 1,000 women who did not participate in the screening, around 5 died of breast cancer within a ten-year period; in a second group of 1,000 women who decided in favor of early detection screening, this number was reduced to 4. In many information leaflets this fact is translated into figures asserting that mammography can reduce the risk by 20% (sometimes even 25 % or 30 % is stated). Based on these, women often draw the conclusion that mammography "saves" 200 out of 1,000 women. The study presented here shows that only1.5% of all interviewed women knew that early detection screening reduces breast cancer mortality by only about one in 1,000 women!

The study focuses on yet another question as well: Are people who more frequently consult physicians or pharmacists better informed about the benefit of early detection screening? Across Europe the answer is again a clear "no". German women in particular, who tend to get their information about early detection screening by consultating with physicians and pharmacists, are not only unable to make reasonable estimates but are even worse informed than those who consult physicians and pharmacists less frequently. The potential causes for this are known from other studies conducted by the Max Planck Institute, which point to flaws in medical education and further training of physicians. This system largely fails neglects training physicians to understand the statistical results of scientific studies and to communicate these to their patients. In addition, students in all schools are generally taught "secure" fields of mathematics, such as algebra and trigonometry, rather than statistical thinking, which would prepare them for dealing with the risks of an insecure world.

Prof. Dr. Gerd Gigerenzer, director of the Harding Center for Risk Literacy, has commented on the findings of the study: "Early detection screening always bears the risk of complications, such as unnecessary operations or incontinence. In order to be able to make an informed decision on whether to participate in screening or not, patients must know about the potential benefits of early detection screening and the potential damage to health. According to the existing scientific studies, the benefit of mammography screening in the age group from 50 to 69 years is a reduction of one in 1,000 women who will die of breast cancer. For early detection screening tests of prostate cancer (PSA tests) the benefit rate is a reduction of zero or one death in 1,000 men. Our European-wide study thus shows that people are simply not aware of these numbers. If we want responsible, well-informed patients, not a paternalistic public health system, this is where we need to start. In a system that is becoming more and more expensive, it is particularly important to inform people precisely and comprehensively in order to give them the competence to make crucial decisions."

Ulla Schmidt, Germany's Health Minister, once envisioned in a speech that patients and physicians should speak to each other "on equal terms". This European-wide study shows that at present, attaining this goal remains an appealing but distant dream.

The Study

Gigerenzer, G., Mata, J., & Frank, R. (2009). Public knowledge of benefits of breast and prostate cancer screening in Europe. Journal of the National Cancer Institute101, 1216-1220. doi:10.1093/jnci/djp237


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