medwireNews: People with type 1 diabetes who take a higher daily dose of insulin may have an increased risk for cancer compared with those on lower doses, US researchers report.
In their analysis of 1303 individuals with type 1 diabetes from the DCCT/EDIC cohort, 7% of whom developed cancer over 28 years of follow-up, the investigators found that the incidence of cancer per 1000 person–years was highest in people with a high average daily dose of insulin (≥0.8 units/kg), at 2.91. This decreased to 2.87 in those taking a medium daily dose (0.5 to <0.8 units/kg), and fell further, to 2.11, in those with a low daily dose (<0.5 units/kg).
Each unit/kg increase in daily insulin dose was associated with a significant 5.93-fold increased risk for cancer in a multivariable analysis model including time-dependent variables, and a 4.13-fold increased risk in a model including time-fixed variables. Women also had a significantly higher cancer risk than men, as did older versus younger people.
Wenjun Zhong (Merck & Co Inc, West Point, Pennsylvania) and Yuanjie Mao (Ohio University, Athens) caution that their study did not demonstrate a causal association and was limited by small participant numbers, “which precluded analyses with specific cancer types and resulted in a wide [confidence interval] for daily insulin dose.”
They conclude in a letter to JAMA Oncology that “larger studies in [type 1 diabetes] are needed to validate this association.”
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