Post-Transplant New-Onset Diabetes Linked to Low Magnesium

LAKE LOUISE, Alberta— Hypomagnesemia may confer an increased risk for new-onset diabetes after transplantation (NODAT) in kidney recipients, according to a new Canadian study.

The Toronto team reviewed the records of 838 people who received kidneys at the Toronto General Hospital between 2000 and 2010. They found lower serum magnesium increases the risk of NODAT by almost 50%, although the increase was not statistically significant.

“If we confirm this association in our follow-up analysis the findings may have implications for post-transplant management of serum magnesium, especially among those at increased risk of NODAT,” lead investigator S. Joseph Kim, MD, a nephrologist, explained to Renal & Urology News after presenting the study at the Canadian Society of Transplantation's 2013 annual meeting. “We have deferred any changes in clinical practice locally until we have the follow-up analysis completed, hopefully the end of September.”

Earlier studies suggested a relationship between hypomagnesemia and NODAT, but there is still no consensus on the existence and strength of the association. The theory is that reduced serum magnesium levels can contribute to insulin resistance, which in turn leads to type 2 diabetes.

To help clarify the relationship, Dr. Kim, Assistant Professor of Medicine at the University of Toronto, and his colleagues analyzed data from adult kidney-transplant recipients in the Comprehensive Renal Transplant Research Information System between January 1, 2000 and December 31, 2010. This database includes all adult patients transplanted at the Toronto General Hospital and other hospitals in Toronto's University Health Network. It includes records of patients' serum magnesium levels before transplant, at one month and three months post-transplant and then every three months after that.

They excluded people who had received simultaneous or prior non-kidney transplants, had diabetes before transplantation, had primary kidney non-function after transplant, had missing lab values or were lost to follow-up.

Three-quarters of the patients (628/838) had low serum magnesium levels before transplantation. The characteristics of the hypomagnesemia and non-hypomagnesemia groups were similar, except the average age of people with normal magnesium levels was a bit higher, at 46.3 versus 43.6 years.

When the investigators analyzed the relationship between NODAT risk and serum magnesium levels over time, at one month post-transplant and rolling averages they found a positive association. For example, every 0.1 mmol/L increase in serum magnesium level at baseline was associated with a 48% decreased likelihood of NODAT. Patients in the lowest quartile of average time-varying and rolling serum magnesium levels, 0.20-0.67 mmol/L, had a 43% increased likelihood of NODAT than those with normal levels, 0.82-1.89 mmol/L.

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