Developing insight over degeneration – study sheds light on potential benefit of influenza immunisation to decreased risk of Parkinson disease

Pushing scientific understanding on degenerative diseases has become a powerful passion for many medical researchers both professionally and personally. Stepping into this space is a group of medical scientists forming an international coalition of researchers. They looked to further insight and options for a disease that has impacted millions. The team’s study looked at influenza immunisation for those in mid-life years, and the impact on risk for Parkinson disease (PD) in the years to come.

With the group calling for more study, encouragingly the data indicates there could be a positive link between immunisation and lower risks of PD, which need to be further explored.

Initial question

The group of scientists from Canada and Germany set out to answer an area of possibility to treat PD with greater efficacy, “is immunization for influenza between age 40 and 50 years associated with a decreased risk of Parkinson disease later during the life course?”

This area of study has been of significant importance to many medical professionals and advocates. PD is the second most common neurodegenerative disease across the globe, not only impacting the lives of the over one million people diagnosed in the U.S but with a greater global footprint, and their caretakers alongside.

Understanding so far

Respected research has shown that PD tends to increase with advancing age, and has higher rates of diagnosis among men than women. Frustrating both researchers and those living with this degenerative disease is the unclear etiology of the disease, that is, the continued mystery as to what triggers the condition.

In noting the current state of the science, that there are “no curative or disease-modifying treatments available, and approved medications mainly alleviate symptoms, such as hypokinesia, rigor, or tremor”, the researchers were compelled to push the understanding forward. While at times slow-paced, gaining greater insight on this disease and potential avenues to gain treatment directionality is persevered by many professionals from personal conviction.

Infection as cause

Starting from prior research which suggested a potential source of PD in infections, “with different bacteria, viruses, and fungi having been suggested as possible causative pathogens over the years”, the team pursued conducting an extensive study to be able to conclude findings from a large sample group.

With the influenza virus being, “the most prominent pathogens in this regard, with preclinical studies suggesting its involvement in the degeneration of dopaminergic neurons and the promotion of α-synuclein phosphorylation and aggregation”, the team wished to see if they could definitively prove not only that there was no negative to being immunised later in life against influenza but that it could have a potential benefit against the risk of PD.

“Several observational studies have shown that influenza infection was associated with an increased risk of PD. A case-control study with a long follow-up also found that influenza infection was associated with an up to 73% increased risk of PD 10 years after infection, which is in line with current evidence regarding a long-term pathogenic process of PD.”

Limited previous sample size

The need for peer-reviewed, extensively researched studies has never been greater in an era of mass misinformation.

The group tackled this head on, understanding the accumulating, albeit still speculative evidence, the researchers noted, “there is a need to understand the potential role of immunization for influenza at midlife as a preventive measure against the development of PD later during the life course.”

“The only population-based study in the area was limited by its small sample size and insufficient follow-up, which led to inconclusive findings and further precluded the assessment of the outcomes of immunization at midlife.”

They state, “To address this important knowledge gap, we conducted a large, population-based cohort study with almost 30 years of follow-up to assess whether immunization for influenza at midlife (between ages 40 and 50 years) is associated with a decreased risk of PD.”

Findings

The researchers assembled, analysed and aggregated a cohort of over a million individuals to conduct their study.

They reviewed the data of, “more than 1 million individuals who received influenza immunization at midlife and their matched controls, influenza immunization at midlife was not associated with the risk of incident Parkinson disease overall.”

And while the “results varied based on seasonality and time since vaccination” and “none of the differences were statistically significant”, the data showed that there were, “potential benefits occurring several years after vaccination or in specific [that] subgroups require further investigation.”

Future implications

While overt causal links were not established, “this cohort study found that influenza immunization at midlife was not associated with the risk of PD in the overall population.” There were however, “potential benefits for PD risk occurring several years after vaccination or in specific patient subgroups require further investigation.”

Many experts in the medical research space have acknowledged difficulty in leaping forward in the complex areas of degenerative conditions. The study is however, a decided move forward in pointing to where further research can focus.

The team stresses that the data shows there is a “potential time-dependent association” between influenza immunisation and decreased risk of PD.

“There was a numerical decrease in the risk of PD over time that reached a maximum of 25% approximately 8 years after the vaccination.”

Seasonal focus

The study further found that there may be greater efficacy to reducing the risk of PD when immunising against influenza within certain seasons, “immunization for influenza at midlife was further associated with a numerical decrease in the risk of PD among individuals vaccinated during influenza season; this result was not observed among individuals vaccinated outside of influenza season.”

While remaining cautious within the bounds of what the data can yield, the researchers are optimistic, “given that the benefits of the vaccine for PD appear more plausible when mediated by the prevention of influenza than by alternative mechanisms, this finding might be in line with a causal association.”

For the millions around the world that are managing this disease, and the scores of loved ones alongside them, the pursuit of further insight and breakthroughs has never been more timely and needed.