But do diabetes and obesity cause cancer? Here’s what blood sugar tests don’t tell you
It is mainly women who bear the brunt of this in the case of diabetes, and men when diabetes is also associated with obesity
Key points
For years, diabetes has been discussed primarily in terms of its traditional complications: heart attacks, strokes, kidney failure, and problems with vision and the peripheral nerves. But there is another issue that is often overlooked: cancers linked to this condition. And the figures emerging from the congress of the European Association for the Study of Diabetes (EASD), currently taking place in Milan, paint a picture that is anything but negligible. Women are particularly affected in the case of diabetes, whilst men are more at risk when diabetes is also associated with obesity.
The Danish study investigating the link between diabetes, obesity and cancer
A study by the Steno Diabetes Centre at Aarhus University (Denmark), presented at the EASD and conducted using health records covering the entire Danish adult population, examined the incidence of cancer over a 27-year period (from 1996 to 2022), comparing outcomes in people with type 2 diabetes with those without diabetes. The result was that, between 2010 and 2022, the overall incidence of cancer was 12 per cent higher in men and as much as 22 per cent higher in women with type 2 diabetes. Between 1996 and 2009, the excess incidence of cancer among people with diabetes had been 9 per cent and 15 per cent, respectively.
The difference becomes even more apparent when looking at obesity-related cancers: between 2010 and 2022, these were 45 per cent more common in men and 30 per cent more common in women with type 2 diabetes than in people without diabetes. Lung cancer was 23 per cent more common in men and 25 per cent more common in women; for colorectal cancer, one of the most common in both sexes, the increase was 17 per cent in men and 14 per cent in women, whilst post-menopausal breast cancer was 8 per cent more common in women with diabetes.
The ratio varies depending on the type of cancer, gender and other factors
These figures must be interpreted correctly. They do not mean that diabetes simply ‘causes’ cancer. This study was designed to ‘capture’ differences in incidence, not to demonstrate a cause-and-effect relationship. Type 2 diabetes, obesity and cancer do, in fact, share a significant number of risk factors: age, being overweight, a sedentary lifestyle, diet and smoking. Distinguishing the contribution made by each individual factor is far from straightforward.
However, the link between diabetes and cancer has a solid biological basis. Insulin resistance, a condition typical of type 2 diabetes, is characterised by the body producing more insulin to compensate for the reduced response of the tissues. And hyperinsulinaemia, together with altered metabolic signalling, chronic inflammation and prolonged hyperglycaemia, is a possible component of the biological environment that may promote the development of certain tumours. However, it is a long way from this biological plausibility to a causal certainty: whilst it is true that diabetes is associated with an increased risk of certain cancers, it is equally true that not all cancers behave in the same way.
