Some viruses, such as the herpes varicella-zoster virus, never leave the infected persons body. Instead, they remain dormant in the central nervous system and flare up occasionally. Yet, the long-term consequences of having certain viruses remain relatively unexplored. However, one study that has come to our attention recently has tried to do this. Here we consider the findings of a study that sought to see whether a cumulative presence of infections would have an impact on cognitive functioning.

The study, which was published in Neurology included a total of 1625 participants. At the start of the study, the participants were 69 years old on average. The studies lasted eight years, and during this time the researchers performed a range of tests and assessments. They analysed blood samples for herpes simplex 1 and 2 and cytomegalovirus. In addition to that, they screened all the participants for Chlamydia pneumoniae and helicobacter pylori. Lastly, they performed annual tests to assess changes in cognitive abilities such as memory. The key findings indicated that a high level of infection was related to an increased risk of memory deficiencies. This association remained even after mental sharpness, education, smoking, heart disease and diabetes were taken into account. However, the researchers were keen to stress that their study reflected an association and not causation. As such, they recommended that further studies be carried out within this field.

Although it looks like an acceptable study on the face of it, we cannot help but feel a bit sceptical about it. One of the reasons for that is that many aspects relating to the rationale were not sufficiently clarified in the publication. In particular, it was not mentioned how long the individuals had had each virus before the researchers detected an increased risk for poorer memory. As such, there was no baseline to compare the findings to. Similarly, we cannot help but feel that a case-control study that sought to give participants a battery of rigorous and reliable cognitive tests would have been more suitable for the type of research that was being carried out. That’s not to say that the current study lacked qualities worth replicating. The sample and the adjustment for confounding variables as well as the long follow up period are commendable. Therefore, it is our hope that further studies aiming to confirm and extend on these findings will be undertaken.