Low Glucose on Last Day in Hospital Link to Death in Diabetes

Patients with diabetes who have hypoglycemia or even low-normal glucose levels in the 24 hours prior to hospital discharge have a significantly increased risk of readmission within 30 days, in addition to a higher likelihood of dying post-discharge, new research shows.

Diabetes is known to increase the risk of hospital readmission by as much as 40%, but the new study, of nearly 850,000 admissions at Veteran Affairs (VA) hospitals over 14 years, suggests that key glucose thresholds — specifically on the day of discharge — could offer important guidance in assessing post-discharge risk.

"Although future studies are needed, physicians should avoid discharging patients with diabetes from the hospital until glucose values above 100 mg/dL are achieved during the last day of the hospitalization," said first author Elias Spanakis, MD, Baltimore VA Medical Center and University of Maryland School of Medicine, in a press release by the Endocrine Society.

Those With Hypoglycemia Have Greater Risk of Dying Post-Discharge

For the study, published online in the Journal of Clinical Endocrinology & Metabolism, Spanakis and colleagues evaluated nationwide data on 843,978 patients with diabetes at VA hospitals from 2000 to 2014, excluding hospitalizations for psychiatric or long-term care, admissions ending in transfer to non-VA hospitals, and admissions with a length of stay exceeding 30 days.

Overall, the 30-day readmission rate among patients was 17.3% and mortality rates at 30, 60, and 180 days were 2.3%, 6.0%, and 10% respectively.

Hypoglycemia (glucose levels < 70 mg/dL) in the last 24 hours of the inpatient stay was present in 9.1% of patients, and 0.6% had severe hypoglycemia (< 40 mg/dL) on the last day in hospital.

After adjusting for factors including age, body mass index, sex, comorbidities, diabetes medications, and other factors, patients with glucose levels indicative of hypoglycemia in the last 24 hours of hospitalization had a 39% higher rate of dying within 30 days of discharge, a 30% higher rate within 90 days, and a 27% higher rate within 180 days, compared to those with normal glucose concentrations (100-109 mg/dL).

For those with severe hypoglycemia in the 24 hours before discharge, the corresponding mortality rates were 124%, 81%, and 66% higher than those with normal glucose levels.

Those with hypoglycemia at discharge were also 20% more likely to be readmitted within 30 days compared to those with normal levels, and with severe hypoglycemia, the 30-day likelihood of readmission was 32% higher.

Key Glucose Thresholds for Increased Risk of Readmission, Death

The key glucose thresholds on the day of discharge that emerged as indicative of an increased risk included levels below 92.9 mg/dL, associated with a higher risk of 30-day readmission, and below 67.3 mg/dL, associated with an increased risk of mortality.

Glucose levels below 87.2 mg/dL were associated with higher combined 30-day readmissions or mortality, compared to patients with glucose levels in the normal range.

"We found that patients with diabetes who are discharged with low or even near-normal glucose values during the last day of the hospital stay are at a higher risk of dying or being readmitted to the hospital," Spanakis noted.

The higher risk of 30-day readmission seen even with a level of 87.2 mg/dL — well within the "low-normal" range of 70 to 93 mg/dL — may be because the level is a predictor of further declines in glucose in the near future, the authors speculate.

"The reasons for the increased risk for readmission for this glucose category [70-93 mg/dL] is unknown, [however] we hypothesize that diabetes patients with glucose levels close to the hypoglycemia range prior to discharge are more likely to develop even lower glucose values after discharge," they write.

Last Day of Hospitalization a "Unique Period" for Modifiable Factors

Despite existing research on overall risks of diabetes and high as well as low glucose levels during hospitalization and readmission, few, if any, previous studies have focused on low glucose levels specifically on the last day of hospitalization as predictors of future outcomes.

But the time period is important as a potentially modifiable factor in longer-term outcomes, such as readmission and death, the authors note.

"The final day of the hospitalization represents a unique period during the inpatient stay, when medications adjustments have been almost finalized, patients are able to tolerate a full diet — minimizing nutritional interruptions and abnormalities in glucose control — and the underlying conditions that necessitated hospitalization have been treated," they explain.

The findings should therefore spur further studies looking at how glucose measures on the last day of hospitalization can be used to identify risk and prevent readmission, the authors emphasize.

"As clinical studies are lacking, large randomized clinical trials are needed to evaluate the impact of improved glycemic control after discharge on clinical outcomes and the effectiveness of innovative strategies on the transition of care."

Spanakis has reported receiving research support from DEXCOM. Co-author Guillermo E. Umpierrez, MD, has reported receiving research support (to Emory University) from Merck, Novo Nordisk, AstraZeneca, Boehringer Ingelheim, and Sanofi. He has also received honorarium for advisory boards/as a consultant from Sanofi and Intarcia Therapeutics. Co-author Soren Snitker, MD, is an employee of Novo Nordisk.

J Clin Endocrinol Metab. Published online May 1, 2019. Abstract

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