Liver and endometrial cancer accounted for high numbers of new cases; increases of these cancer types have been attributed to rising rates of diabetes and obesity.
Diabetes and being overweight caused 5.6% of all new cancer cases worldwide in 2012, or nearly 800,000 cases, according to an analysis published this week in the journal The Lancet Diabetes & Endocrinology.
While several researchers have highlighted the rise in cancers tied to obesity—especially soaring rates of liver cancer—this is the first study to quantify just how many cases can be attributed to the related epidemics of diabetes and being overweight.
To come up with their global estimate, the Lancet authors collected data on new cases of 12 types of cancer from 175 countries for 2012, which was then paired with data on body mass index (BMI) and diabetes rates. They matched the data by age and gender and looked back at corresponding BMI and diabetes data from 2002, estimating a 10-year lag before cancer materializes once diabetes or high BMI is present. With this method, they found that 792,600 new cancer cases in 2012 could be attributed to diabetes or high BMI. For this study, researchers assumed cancers were attributable to a BMI of at least 25 kg/m2, which is the CDC cutoff for being overweight. Obesity is defined as having a BMI of 30 kg/m2 or higher.
Liver and endometrial cancer were the most common cancers linked to diabetes and high BMI. Overall, 24.5% new liver cancers and 38.4% of new endometrial cancers were attributed to these chronic conditions; however, the authors noted that liver cancer is even more prevalent in high-income Asia Pacific and east and southeast Asian countries, where diabetes or high BMI were linked to 30.7% and 53.8% of these cases, respectively. Endometrial cancer is more common in high-income western countries.
Earlier this year, CDC identified 13 cancers that accounted for 40% of all new cases in the United States, including liver, endometrial, and cancers of various organs of the digestive system. CDC officials said they were alarmed that these cancers were showing up in younger patients, suggesting that nation’s problem with diabetes and obesity was driving cancer risk down to younger members of the population, and along with it, rising healthcare costs.
The connections among diabetes, obesity, and cancer are complex; both genetic and lifestyle factors are involved. Excess weight can trigger inflammation, which leads to increased insulin and estrogen production. This can cause cells to divide faster than normal, leading to the development of tumors.
Cancer from diabetes or high BMI occurs in both wealthy countries and poor ones. While most of the cancers tied to diabetes and being overweight occur in high-income western nations (38.2%), the next high share can be found in east and southeast Asia, with 24.1% of the cases. In developing countries, the effects of diabetes and being overweight are uneven, causing 9% to 14% of all cancer cases in Mongolia, Egypt, and Kuwait but only around 1% in the East African nations of Tanzania, Mozambique, and Madagascar.
Given rising worldwide rates of diabetes and obesity, the share of cancers they cause is only expected to grow, according to the study’s authors. The World Health Organization (WHO) estimated that 1.9 billion adults, or 39% of those over 18, were overweight in 2016. The WHO estimates that 422 million people have diabetes. The share of the population with diabetes climbed from 4.7% in 1980 to 8.5% in 2014.
“As the prevalence of these cancer risk factors increases, clinical and public health efforts should focus on identifying preventive and screening measures for populations and for individual patients. It is important that effective food policies are implemented to tackle the rising prevalence of diabetes, high BMI and the diseases related to these risk factors,” said lead author Jonathan Pearson-Stuttard, BMBCh, Imperial College London, United Kingdom, in a statement.
Pearson-Stuttard J, Zhou B, Kontis V, Bentham J, Gunter MJ, Ezzati M. Worldwide burden of cancer attributable to diabetes and high body-mass index: a comparative risk assessment [published online November 28, 2017]. Lancet Diab Endocrinol. 2017; doi: 10.1016/S2213-8587(17)30366-2.