A lifestyle that increases the risk of cardiovascular disease also raises the risk of developing several types of cancer.
LIFESTYLE: People who have a lot of the risk factors for cardiovascular disease are also at increased risk of getting colon, stomach or oesophageal cancer, according to three recent studies of nearly 200,000 Norwegians. Abdominal obesity may be a particularly crucial factor.
“Our findings show that cancer, like cardiovascular disease, is closely linked to lifestyle factors such as obesity, blood pressure and levels of triglycerides,” says NTNU researcher Eivind Ness-Jensen, who is one of the authors of the studies.
Researchers from Norway and Sweden have used data from eleven large Norwegian population surveys that total more than 193,000 Norwegians. The researchers followed the participants through the end of 2010, and compared the risk of various cancers in participants with and without metabolic syndrome, a condition that involves a high risk of cardiovascular disease.
Approximately one in four Norwegian adults has metabolic syndrome, defined by a large waistline, high blood pressure, unhealthy cholesterol profile and high blood sugar.
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Increased risk of colon cancer
Every year, about 3,600 Norwegians are diagnosed with colorectal cancer. It’s among the most common forms of cancer.
One of the three studies shows about a 26% increased risk of these cancers in people who have metabolic syndrome, and the results were recently published in the highly acclaimed American Journal of Epidemiology. For men, the risk of cancer in the upper colon saw greater increases, whereas women with metabolic syndrome had a 52% higher risk of rectal cancer.
Ness-Jensen also observed that the individual factors of a large waistline, high blood pressure and high triglycerides— or fat in the blood— were associated with an increased risk of colorectal cancer.
In another study published in the journal Epidemiology, the researchers looked closely at the relationship between body composition and colon cancer, and showed that high BMI—unlike a large waistline—was not associated with increased risk.
“This suggests that abdominal obesity, but not general obesity, contributes to the development of colon cancer. Previous studies have shown that belly fat produces inflammatory substances that have direct carcinogenic properties,” says Ness-Jensen.
Risk of stomach and oesophageal cancer also up
Stomach cancer kills more than 300 Norwegians every year. Metabolic syndrome was associated with a 44% increased risk of stomach cancer, and in women a large waistline, high blood pressure and high blood sugar levels were associated with increased risk.
The researchers believe the increased risk of stomach cancer may be because metabolic syndrome and its defining risk factors cause chronic inflammation. Other possible mechanisms may be problems with gastrointestinal motor function, decreased insulin sensitivity and changes in the hormonal environment.
According to Ness-Jensen, the researchers were not able to detect any definite association between metabolic syndrome and oesophageal cancer, but found that a larger waistline was also was a risk factor for developing this cancer. One possible reason for this could be a higher incidence of acid reflux in obese individuals.
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Can’t rule out more correlations
One strength of the study is that the researchers have been able to adjust the analyses for a wide range of factors that may affect the relationship between metabolic syndrome and cancer.
The results are also based on standardized measurements of all the risk factors and reliable information on cancer diagnoses from the Cancer Registry of Norway.
The relatively low number of people who contracted gastric or oesophageal cancer during the follow-up period reduces the probability of detecting weaker correlations, and scientists cannot rule out the possibility of more links between the risk factors for cardiovascular disease and cancer development than were identified in these three studies.
“Our findings are important because they show that lifestyle factors that may cause cardiovascular disease are also concerning for cancer development,” says Ness-Jensen.