Lyme neuroborreliosis: How unique Danish registry data can benefit patients

In Europe, Lyme borreliosis is a common tickborne human infection. When the disease causes neurological symptoms (often facial paralysis), it gives rise to major concern. Patients ask: “Can you treat me and get me back to my daily life?” In our more than 30 years of experience in infectious diseases, we have not been able to give good answers to the questions often asked of us by our patients. Publications about people who are severely ill for years, following reported Lyme borreliosis, abound on the internet. Some scientific literature seems to emphasise the frequency and severity of long term complications. Most existing research on Lyme neuroborreliosis looks at small patient populations with no control cohorts.  

We have previously used Danish registers to study the long term outcomes of central nervous infections. These studies demonstrated that infections of the central nervous system, such as pneumococcal meningitis and herpes simplex encephalitis, were associated with substantially decreased employment, lower education, and increased need for disability pension. Inspired by these studies, we linked these national registers with local registers of Lyme borreliosis tests. We found that most people continue their usual life after being treated for Lyme neuroborreliosis. We have to emphasise, however, that this study focuses on Lyme neuroborreliosis, and is not designed to answer questions regarding the post-treatment of Lyme disease syndrome (PTLDS).

An important aspect of the paper was access to data from national Danish registries. Denmark has a tax funded national public health system, and its registry allows researchers to follow various aspects of life in the population. Danish authorities offer scientists access to these data through research facilities, which observe strict security. We were, therefore, able to undertake a population based nationwide study that included more than 2000 patients and a well designed control population. We were able to follow the patients before their diagnosis of Lyme neuroborreliosis, as well as their family members. We therefore assume that our study populations are representative of general Lyme neuroborreliosis patients and the Danish background population.

Surprisingly, our study showed an association between a diagnosis of Lyme neuroborreliosis and hematologic cancer and skin cancer. We believe this to be a true association, but cannot exclude the possibility that it is a random finding. Our hypothesis is that the association is caused by a common risk factor, for example, an immunological predisposition, rather than a consequence of infection with Borrelia.

We are aware that Lyme neuroborreliosis may give rise to residual symptoms that may lead to social consequences. This aspect is also confirmed in our study. However, access to subjective information on the internet and social media can cause concern, anxiety, and insecurity. We find that a main object for modern epidemiology is to use patient data to reassure patients of a benign prognosis, when justified. Danish registry data are probably the best in the world for this purpose. Currently, some Danish authorities are discussing reducing researchers’ access to these data, which would be a regressive move. Denmark has generated some unique data. The country has a responsibility to ensure that it can benefit Denmark, as well as the international community. Our study demonstrates how these data can benefit patients.

Finally, we can use the results of the study in our daily clinical work to reassure patients, and provide answers to their questions: “Yes, neuroborreliosis is a severe and unpleasant disease, but it can be treated, and almost all patients get back to their daily lives.”

Niels Obel is a consultant and professor in infectious diseases, Copenhagen University Hospital, Denmark. His major research interest is long term consequences of infectious diseases.




Anne-Mette Lebech is a consultant at the Department of Infectious Diseases, Denmark, and her research interest is Lyme borreliosis.





Ram B. Dessau is a consultant in clinical microbiology, Slagelse Hospital, Denmark, and Lyme borreliosis has been a main focus of his research.

Competing interests: Please see statement on research paper.