No association between higher insulin doses and raised cardiovascular risk, study reports

Adults with type 2 diabetes who were treated with higher insulin doses had no increased cardiovascular risk, a Canadian study finds.
Scientists at the School of Pharmacy at Memorial University of Newfoundlands in St John’s, Canada say their findings should reassure both patients and clinicians of the overall safety of insulin use in treating type 2 diabetes.
John-Michael Gamble, PhD and colleagues added that the results could help explain why certain studies have called into the question in the safety of insulin therapy in patients with type 2 diabetes.
The study team analysed healthcare records from 6,072 adults with type 2 diabetes, all of whom were aged 30 years or over and had began metformin monotherapy from 2001 to 2012, and were new users of insulin. A subcohort of 3,599 patients was included based on hospital records and death certificate information.
The patients were categorised into five groups depending on their mean insulin dose per day (up to 100 units) and all-cause mortality. During follow-up they were assessed within 180-day time segments – the average (median) period the participants were followed for was 3.1 years.
These results were then stratified by three categories of insulin use for cardiovascular events: less than 50 units per day; 50 to less than 100 units per day; and at least 100 units per day.
At first, higher insulin doses were associated with increased mortality, but adjustments for changes in blood sugar control, weight, frequency of hypoglycemia and occurrence of cardiovascular events decreased this association.
Furthermore, no significant associations were observed between higher insulin doses and cardiovascular events.
The researchers wrote: “Existing studies have shown conflicting evidence regarding the safety of exogenous insulin therapy in patients with type 2 diabetes. In particular, observational studies have reported an increased risk of death and cardiovascular disease among users of higher versus lower doses of insulin.
“These findings could partly explai, and help to reconcile, the opposing conclusions reached by previous observational studies and randomized trials with respect to the safety of insulin.
“Overall, the result from this study reassures both patients and their physicians of the overall safety and absence of major [CV] harms of insulin use in the treatment of type 2 diabetes.”
The study was published online in The Lancet.