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Higher-risk people are shunning colon cancer screens

August 07, 2017

An acknowledged problem in public health surveys is that those who take part are generally more health conscious and healthier than those who do not. If this is also true of colon cancer screening, it means, at worst, that the people at greatest risk of developing the disease are not being screened, even though they would benefit most from the procedure.

A new study from Karolinska Institutet has confirmed these fears. Nine years ago, a team of researchers invited 2,000 people between the ages of 59 and 61 to take part in a colon cancer screening programme. Thirty-nine per cent of them accepted, but 61 per cent chose not to. A follow-up of these two groups has now shown that a larger percentage of the non-participants have since developed colon cancer or died, either from colon cancer or other diseases, compared with the participants.

???We do not think that the difference in incidences of cancer and death between the two groups is due to any effect the screening might have had, but believe it was down to the selection of people who took part,??? says Johannes Blom, one of the researchers behind the study. ???What we have here is the self-selection of more health conscious and healthier people , who perhaps don??t benefit as much from taking part.???

The team believes that those who opted out of the programme have less healthy lifestyles. This is supported by the findings that more of the non-participants have developed other forms of smoking-related cancer and that they run more than double the risk of dying from cardiovascular disease.

???If higher-risk people choose not to take part, public screening programmes will become very cost inefficient,??? says Dr Blom. ???One of the greatest challenges is therefore to encourage participation, so that the less motivated are also screened.???

On 1 January, the Stockholm County Council became the first health authority in Sweden to launch a screening programme for colon cancer.

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FMD measurements can provide valuable information about a person's cardiovascular health. Previous studies have shown that people with an impaired FMD response have an increased risk of heart attack, need for bypass surgery or catheter procedure to open clogged coronary arteries, and even death from heart disease.

Dr. Kelm speculated that cocoa flavanols improve FMD response by increasing the production of nitric oxide, the chemical signal that tells arteries to relax and widen in response to increased blood flow. Relaxation of the arteries takes stress off of the heart and blood vessels.

The high-flavanol cocoa used in this study-which provided many times more flavanols than the typical U.S. dietary intake of 20 to 100 mg daily-is not sold in the supermarket. Dr. Kelm cautioned that the take-home message of the study is not that people with diabetes should guzzle cocoa, but rather, that dietary flavanols hold promise as a way to prevent heart disease.

"Patients with type 2 diabetes can certainly find ways to fit chocolate into a healthy lifestyle, but this study is not about chocolate, and it's not about urging those with diabetes to eat more chocolate. This research focuses on what's at the true heart of the discussion on "healthy chocolate"-it's about cocoa flavanols, the naturally occurring compounds in cocoa," he said. "While more research is needed, our results demonstrate that dietary flavanols might have an important impact as part of a healthy diet in the prevention of cardiovascular complications in diabetic patients."

Umberto Campia, M.D., who co-wrote an editorial about the new study in the same issue of JACC, noted that diabetics are an ideal population in which to study the effects of flavanols on arterial function, because high blood sugar damages the endothelium and because these patients have a high risk of cardiovascular disease.

Any therapy that helps the lining of the arteries to function better is potentially important, said Dr. Campia, a research associate with MedStar Research Institute in Washington, D.C.. "The endothelium is one of the largest organs in the body," he said. "It maintains the health of the arteries and prevents blockages that can cause heart attacks, strokes and limb loss."

"This study is important and thought-provoking," he noted. "We now have sizeable evidence that cocoa flavanols have a positive effect on the health of the arteries. This is the foundation we need for doing a much larger prospective study that looks at the effect of cocoa flavanols not just on endothelial function, but also on the risk of heart attack, stroke, and other serious forms of cardiovascular disease."

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