Higher insulin dose is positively associated with cancer incidence, finds a study.

The study, published in JAMA Oncology, looked at the correlation between daily insulin dose and cancer incidence (the number of new cases) among patients with type 1 diabetes, and also found the association is stronger among those with insulin resistance.

The results showed that traditional metabolic factors such as obesity (represented by body mass index), sugar control (represented by Haemoglobin A1c), and blood pressure control do not associate with cancer incidence in patients with Type-1 diabetes.

"However, cancer incidence was higher for those who took large doses of insulin," said Yuanjie Mao, assistant clinical professor at Ohio University in the US.

Our results implied that clinicians might need to balance the potential cancer risk when treating patients with Type 1 diabetes on a high daily insulin dose or that improving insulin sensitivity may be preferred over simply increasing the insulin dose," he added.

The study also found that age and sex are associated with cancer incidence when evaluated separately and that a daily insulin dose posed a higher risk of cancer than age, especially a higher insulin dose.

Specifically, women were found to carry a higher risk than men; however, it was unclear what risk factors may contribute to the higher cancer incidence in Type 1 diabetes.

Although previous studies have concluded that patients with diabetes have a higher risk of cancer in general, this is the first study to explore the associated cancer incidence factors in Type 1 diabetes.

Mao explained:

"Type 1 diabetes accounts for an estimated five to 10 per cent of all diabetes cases, and recent studies in Type 1 diabetes also found a higher incidence of certain cancers such as stomach, liver, pancreas, endometrium and kidney cancers in the population compared with the general population. Whereas, in Type 2 diabetes, the increased risk is attributed to metabolic factors such as obesity, chronic inflammation status, and insulin resistance."