For months now, it’s been clear that diabetes is a major risk factor for worse outcomes in people who develop COVID-19. Study after study has shown that people with diabetes are more likely to be hospitalized with the viral illness, and to experience worse outcomes — including a higher risk of death — if they are hospitalized with the disease.
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But it’s not all doom and gloom for people with diabetes when it comes to COVID-19 risk. Studies have also shown that good blood glucose control can significantly improve outcomes related to COVID-19. What hasn’t always been clear, though, is how much glucose control can affect outcomes after people are hospitalized with the illness — as opposed to how outcomes are affected by a person’s previous blood glucose control, as shown by their glucose level or HbA1c (a measure of long-term blood glucose control) when they’re admitted to the hospital.
But a new study adds support to the idea that good blood glucose control is an important factor in COVID-19 outcomes even after a person is admitted to the hospital with the illness.
Better glucose control in hospital reduces death risk
Published in the journal Diabetes Care, the study looked at 1,544 people hospitalized with COVID-19 across 91 hospitals in 12 U.S. states. In addition to looking at patients’ blood glucose levels at the time of their hospital admission — as some previous studies have done — researchers looked at glucose levels on day two of their hospital stay for ICU (intensive care unit) patients, and day two or three for non-ICU patients. These “achieved” glucose levels were then compared with outcomes related to the hospital stay, including the risk of death.
The study participants were grouped into four categories based on their achieved blood glucose levels: 140 mg/dl or lower, 141–180 mg/dl, 181–250 mg/dl, and greater than 250 mg/dl. Overall, 18.1% of the patients died during their hospital stay.
The researchers found that in non-ICU patients, a blood glucose level greater than 250 mg/dl on day two or three was independently associated with a much higher risk of death than in those with a lower glucose level — over seven times as high, in fact. This contrasts with the researchers’ finding that blood glucose levels at the time of hospital admission were far less likely to be associated with the risk of death. Based on glucose levels at the time of admission, those with a level greater than 250 mg/dl were only about 1.5 times as likely to die as those with a lower glucose level — a difference that wasn’t even found to be statistically significant, meaning that it could have been due to chance or other factors.
In patients who were directly admitted to the ICU, though, the picture was somewhat different. In this group, a glucose level greater than 250 mg/dl at the time of admission was associated with a death risk over three times as high as in those with a lower glucose level. In contrast, a glucose level greater than 250 mg/dl on day two of their hospital stay was associated with a death risk only about 1.4 times as high as in those with a lower glucose level — not a statistically significant difference. But a glucose level below 70 mg/dl — the threshold for hypoglycemia (low blood glucose) — was found to increase the risk of death by a factor of about 2.2, a significant difference.
Lessons for glucose management?
While the results of any single study shouldn’t be seen as definitive, this study does suggest that there are differences between ICU and non-ICU patients hospitalized for COVID-19 in terms of when blood glucose control matters the most in reducing or raising the risk of death.
In ICU patients — those with the most severe cases of COVID-19 — glucose levels at the time of hospital admission were a much better predictor of death risk than glucose levels achieved on day two of their hospital stay. But in non-ICU patients with less severe COVID-19, glucose levels on day two or three of their hospital stay were a better predictor of death risk than glucose levels at the time of hospital admission.
Together, these findings suggest that there may be a certain point in the course of COVID-19 when blood glucose control is most closely tied to the risk of death. It’s possible that non-ICU patients mostly haven’t reached this stage of the disease at the time of their hospital admission, while ICU patients have already reached it — so that further efforts to achieve good blood glucose control have little to no effect on their risk of death.
If this theory is valid, then it means that people with diabetes should double down on achieving good blood glucose control in case they develop COVID-19 — especially a severe case that gets them admitted to the ICU. But it also means that, especially for patients who aren’t in the ICU, it’s essential for medical professionals to effectively manage glucose levels of people hospitalized with COVID-19.