Diabetes is a chronic disease affecting hundreds of millions worldwide and has multiple risk factors. The more the risk factors present, the higher the likelihood of developing diabetes. Understanding these factors is essential for prevention. A new study published in The Lancet Diabetes and Endocrinology describes a link between COVID-19 and diabetes.
From databases of tens of millions of people in England registered with their general practitioners, researchers examined the risk of developing diabetes following COVID-19. They found a four-fold increase in risk during the first month post-infection. The risk remained elevated in two-thirds of these individuals in the second year.
Early indications came in 2020 when doctors across the world noted a surprisingly high occurrence of diabetes in previously healthy individuals following a diagnosis of COVID-19. Some required high doses of insulin. A paper published in the Journal of Family Medicine and Primary Care in October 2022 from Telangana reported similar findings.
However, observations based on small numbers of patients are not always definitive. For instance, steroid use for COVID-19 raises blood sugar levels on its own. Besides, in any population, diabetes exists undetected in a significant proportion of individuals. This might have been unearthed only because of the medical attention they received after contracting COVID. A reverse causality has also been implicated, with people with diabetes being at greater risk for severe COVID-19. It was also unclear whether the rise in blood sugars would settle down after the immediate stress of COVID passed. Thus, the link remained a matter of debate, necessitating larger studies over an extended period of time.
The new study also examined health records from before and after the vaccine rollout, enabling researchers to investigate the impact of vaccination on diabetes risk. With a follow-up period exceeding a year, they could assess the persistence of newly diagnosed diabetes. Since the study relied on well-maintained databases from before the pandemic, the findings are unlikely to be due to increased testing alone. The persistence of diabetes into the second year indicates that steroid use alone was not responsible.
Two key observations linked the severity of COVID-19 to an increased risk of diabetes. Firstly, the risk was significantly higher among hospitalised patients. Secondly, vaccinated individuals, who experienced less severe COVID-19, had a lower risk of developing diabetes.
When comparing vaccinated and unvaccinated populations, it is important to address demographic differences. For instance, unvaccinated people in England tended to be younger, healthier, and more likely to be of South Asian or Black ethnicity. Although South Asians have a higher baseline risk of diabetes, younger age lowers the overall risk in a population. To ensure accurate conclusions, the researchers adjusted for these factors, eliminating any inaccuracies from comparing unequal populations.
The increased diabetes risk following COVID-19 is believed to involve at least two mechanisms. The receptors used by the virus to attach and enter human cells are also found in the insulin-producing beta cells in the pancreas. Therefore it is possible the virus might have damaged these cells. Additionally, the widespread inflammation caused by COVID-19 leads to insulin resistance. Besides adding to the body of evidence connecting chronic diseases and viral infections, the study enhances our understanding of the various mechanisms involved in the development of diabetes. In summary, COVID-19 has increased the burden of chronic diseases among survivors in several ways, with diabetes being one of them.
(Rajeev Jayadevan is co-chairman of the National IMA COVID task Force)
