The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causal agent of the coronavirus disease 2019 (COVID-19). A recent eClinicalMedicine study investigates whether people with diabetes are more prone to develop long COVID, which is defined as the prolonged persistence of symptoms following SARS-CoV-2 infection.

Study: The prevalence of long COVID in people with diabetes mellitus–evidence from a UK cohort. Image Credit: Dragana Gordic / Shutterstock.com

What causes long COVID?

Long COVID has been described as the persistence of symptoms or development of a multi-system syndrome after recovering from the initial SARS-CoV-2 infection. Some common features of long COVID include muscle weakness, concentration impairment/brain fog, fatigue, and malaise. Other less frequent symptoms of long COVID are chest pain, headaches, excess perspiration, anxiety, and sore throat.

Although scientists have identified several factors that contribute to the development of long COVID, few studies have explored the prevalence of long COVID at the population level. Understanding whether this prevalence varies by a specific comorbidity is essential. 

About the study

The current retrospective observational cohort study explored the prevalence of long COVID in the United Kingdom population. The researchers were particularly interested in studying people with diabetes, as several studies have confirmed that people with a history of diabetes mellitus are at a greater risk of developing adverse sequelae of acute SARS-CoV-2 infection.

All relevant electronic health record (EHR) data were obtained from the Greater Manchester Care Record (GMCR). This database hosts the Primary Health Care records of approximately 2.87 million people in Greater Manchester. 

The current study investigated whether people with type 1 diabetes (T1D) or T2D were susceptible to developing long COVID following SARS-CoV-2 infection. To this end, individuals with a history of T1D or T2D and COVID-19 confirmed through polymerase chain reaction (PCR) testing were considered.

Each participant with T1D or T2D was matched by age and sex with healthy or non-diabetic controls. Importantly, all study participants tested positive for COVID-19, even 28 days after recovering from the initial infection.

Study findings

A total of 3,087 T1D individuals were matched with 14,077 non-diabetic controls, whereas 3,087 individuals with T2D were matched with 14,077 non-diabetes controls. The mean age of individuals diagnosed with T1D and T2D was 47 and 65, respectively. All patients with T1D were treated with insulin, whereas those with T2D were treated with insulin and oral hypoglycaemic agents. 

The researchers assumed that individuals with T2D regularly attend general practices to monitor their condition. This increases the likelihood of being diagnosed with long COVID more efficiently.

A lower number of long COVID diagnoses or referrals were associated with people with T1D at 0.33% as compared to 0.48% for matched controls. Compared to men with T2D, matched non-T2D controls were less likely to develop long COVID.

The prevalence of long COVID was higher in matched controls as compared to women with T2D. Both males and females with T2D exhibited a similar prevalence of long COVID.

A bidirectional association was observed between long COVID, T2D, and acute COVID-19. Those with a higher body mass index (BMI), younger females, or of mixed ethnicity who were diagnosed with T2D were at a greater risk of developing long COVID.

It is possible that younger females with T2D were more susceptible to long COVID due to the tendency of this group to visit general practices more frequently than males.

Strengths and limitations

The current study’s key strength is its cohort, which included all general practices in Greater Manchester. Furthermore, only participants accurately diagnosed with diabetes were considered for the analysis. Another strength of this study is the consideration of the wide-ranging COVID-19 pandemic period from its onset to September 2023.

Consistent with previous reports, the current study also acknowledges that the diagnosis of long COVID is a subject of variability. Although it is possible to underreport people with acute SARS-CoV-2 infection, the number of diabetic and non-diabetic people remained constant.

Another limitation is the exclusion of people with other forms of diabetes, such as diabetes due to maturity-onset diabetes of the young (MODY) or secondary to pancreatitis.

Despite these limitations, the current study highlighted that individuals with T2D develop long COVID at a higher rate. Thus, more research is needed to identify the different factors that increase the risk of developing long COVID.