Clinical lessons for diabetes treatment from the COVID-19 pandemic

A high rate of severe Coronavirus Disease 2019 (COVID-19) illness and mortality in people with diabetes was recognized from the early period of the pandemic. Indeed, many individuals with diabetes, especially older patients, feared leaving home even as the pandemic waned. While extreme caution may well have prevented some instances of infection, it also increased distress and disease stigma as well as physical inactivity in the effort to avoid contact with people who may be infected. Interruption of treatment can negatively impact clinical glycemic management and lead to the development of diabetic complications. Fear of infection also was a factor in the disruption of optimal management for patients with type 1 diabetes, many of whom are relatively young and for whom regular treatment with insulin is essential. Although Japan has a national health insurance program, all costs are not covered, and financial distress also impacted the maintenance of optimal diabetes care.

Moreover, although Japan has a robust health checkup system as well as a health insurance program, many individuals with diabetes nevertheless remain undiagnosed; Uchihara et al.¹ report that patients hospitalized for COVID-19 infection, who are newly diagnosed with diabetes, progress to a critical condition at more than twice the rate of those already under diabetes management and show higher levels of HbA1c and inflammatory markers and require more oxygen. Moreover, it is especially difficult to manage glycemia in the early phase of COVID-19 treatment in such patients; steroid drugs, the recommended treatment for infection in cases of moderate to severe pneumonia, can exacerbate hyperglycemia. They also report that while both individuals with undiagnosed diabetes and those under treatment have worse COVID-19 outcomes including invasive mechanical ventilation, extracorporeal membrane oxygenation support, intensive care unit admission, and transfer to another medical facility for more advanced care as well as in-hospital death when compared with those who do not have the disease, individuals with undiagnosed diabetes exhibit an acute glycemic deterioration upon COVID-19 infection that poses a substantial additional risk. Interestingly, only those individuals receiving treatment for diabetes who had poor glycemic management (HbA1c ≥8.0%) were found to have worse COVID-19 outcomes, indicating that it is hyperglycemia rather than diabetes itself that exacerbates COVID-19 outcomes². Moreover, during the first year of the pandemic, Okada et al.³ reported lower susceptibility to COVID-19 infection among individuals with diabetes who maintained optimal HbA1c management goals. Thus, the management of glycemia in diabetes on a routine basis not only mitigates the severity of COVID-19 infection should it occur, but also may reduce the infection rate.

In the early summer of 2020, just after the advent of the pandemic, we conducted a questionnaire-based survey on the association of lifestyle and changes in body weight and HbA1c in individuals with diabetes⁴. Older individuals with diabetes were found to be more likely to have increased body weight due to reduced activity in daily life, resulting in poorer glycemic management. Changes in body composition in such individuals may well be the more important long-term impact of COVID-19 pandemic on diabetes management due in part to its age-related exacerbation. Tsukaguchi et al.⁵ report that poorer glycemic management is associated with changes in body weight, especially body fat mass and percentage, but not with changes in skeletal muscle mass or skeletal muscle index. They also note that the impact on body fat mass is more pronounced in older individuals.

Thus, the importance of maintaining a lifestyle that reduces obesity and physical deterioration as well as maintaining appropriate glycemic management in individuals with diabetes during coronavirus pandemics must be emphasized. Although more than 4 years have passed since the first appearance of COVID-19, much is still unknown regarding the long-term impacts of COVID-19 on diabetes treatment. However, it is evident that an inactive lifestyle and the resultant increase in body fat percentage can complicate glycemic management and lead to worse infection outcomes. Considering the possibility of future coronavirus pandemics, the optimal management of blood glucose and body weight and composition in diabetes patients in response to the challenge is therefore paramount (Figure 1).

Y Hamamoto received speaker fees from Novo Nordisk Pharma, Eli Lilly Japan, Daiichi Sankyo and Mitsubishi Tanabe Pharma, Taisho Pharmaceutical, MSD and Sumitomo Pharma, and received a research grant from Sumitomo Pharma and Nippon Boehringer Ingelheim. Yoshiyuki Hamamoto is an Editorial Board member of Journal of Diabetes Investigation and the author of this article. To minimize bias, he was excluded from all editorial decision-making related to the acceptance of this article for publication.

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