Preexisting prediabetes and the severity of COVID-19.

To the Editor,

The emergence of a novel coronavirus disease (COVID-19) in Wuhan, China, is spreading rapidly across the globe. A frequent preexisting comorbidity in COVID-19 patients is type 2 diabetes [1]. Several reports published in Primary Care Diabetes and elsewhere have consistently shown that preexisting type 2 diabetes is associated with the disease severity of COVID-19. This includes increased episodes of acute respiratory distress syndrome, intensive care unit admission, mechanical ventilation, and mortality [2,3]. However, the impact of preexisting prediabetes on the course of this disease is far less well studied.

Prediabetes and type 2 diabetes share similar pathophysiology, with the two primary defects being impaired insulin secretion and insulin resistance [4]. Most importantly, the key underlying mechanisms behind the severity of COVID-19 in known type 2 diabetes patients, including chronic low-grade inflammation, impaired innate immunity, poor adaptive immune response to infections, and pro-coagulative state [2], also characterize the prediabetes phenotype, although to a lesser degree than type 2 diabetes [4]. Thus, it can be hypothesized that people with preexisting prediabetes could also experience poor outcomes of COVID-19. For example, in a study by Li et al. in China, out of 453 hospitalized COVID-19 patients, 129 (28.5%) had possible preexisting prediabetes (fasting plasma glucose (FPG) 5.6–6.9 mmol/l and/or HbA1c 5.7–6.4%) [5]. This was associated with a trend towards a higher risk of mortality (Hazard ratio 3.30, 95% CI 0.65, 16.6), compared with those with normal glucose. In a large suburban hospital study from New Jersey, among 184 hospitalized COVID-19 patients, 44 (23.9%) had preexisting prediabetes (HbA1c 5.7–6.4%) [6]. Slightly more than 50% of these patients had persistently elevated FPG in the absence of steroid therapy. These preliminary observations suggest that preexisting prediabetes is much more prevalent in COVID-19 patients than known type 2 diabetes (7 to 17% depending on the disease severity) [1]. They also provide early indications for a possible association between preexisting prediabetes and COVID-19 disease severity. However, large-scale observational studies are required to study this relationship further. To ascertain the status of preexisting prediabetes, it is essential that clinicians utilize the electronic medical records and/or screen all COVID-19 patients with HbA1c in addition to blood glucose [7].

Compared with type 2 diabetes, prediabetes is highly common, the prevalence is rapidly increasing, and most people are unaware of their high-risk status [8]. Thus, even its minimal influence on COVID-19 can impact a large number of individuals. It is therefore crucial to understand the link between preexisting prediabetes and the severity of COVID-19.

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Conflict of interest

None of the authors have any conflict of interest.