A gut feeling about gut feelings

At the Movement Disorders meeting held in Berlin two weeks ago, there was an interesting presentation dealing with a topic close to our hearts (literally).

In a previous post, we have discussed research suggesting that people (Danes) with vagotomies (severing of the nerves from the stomach to the brain) have a reduced risk of Parkinson’s disease – supporting the idea that perhaps the gut is a one site of disease initiation (click here to read that post).

At the meeting in Berlin, however, data was presented that failed to replicate the findings in a separate group of people (Sweds!).

Title: Vagotomy and Parkinson’s disease risk: A Swedish register-based matched cohort study
Authors: B. Liu, F. Fang, N.L. Pedersen, A. Tillander, J.F. Ludvigsson, A. Ekbom, P. Svenningsson, H. Chen, K. Wirdefeldt
Abstract Number: 476 (click here to see the original abstract – OPEN ACCESS)

The Swedish researchers collected information regarding 8,279 individuals born in Sweden between 1880 and 1970 who underwent vagotomy between 1964 and 2010 (3,245 truncal and 5,029 selective). For each vagotomized individual, they  collected medical information for 40 control subjects matched for sex and year of birth (at the date of surgery). They found that vagotomy was not associated with Parkinson’s disease risk.

Truncal vagotomy was associated with a lower risk more than five years after the surgery, but that result was not statistically significant. The researcher suggested that the findings needs to be verified in larger samples.

Differences between the studies?

The Danish researcher analysed medical records between 1975 and 1995 from 5339 individuals had a truncal vagotomy and 5870 had superselective vagotomy. The Sweds on the other hand, looked over a longer period (1964 – 2010) but at a smaller sample size (3,245 truncal and 5,029 selective).

Conclusions?

We must note here that the current research has not been peer-reviewed and we are presenting it here for interests sake. But it come after a series of correspondence regarding the original Danish paper were published in the journal Annals of Neurology. Those letters to the editor were from a group of researchers (believe it or not, mainly Norwegians) reported that an analysis of the same data sets used in the original study failed to find a significant difference between the groups – that is, no protective effect for vagotomies in Parkinson’s disease.

This Scandinavian debate has important implications for Parkinson’s disease, bringing in to question the idea that Parkinson’s disease may begin in the gut. Recently, there have also been several reports published suggesting that alpha synuclein present in colonic biopsies may not be as useful in diagnosing Parkinson’s disease as previously proposed.

And this is why the path of science is such a long one – interesting new findings need to be replicated before they can be added to our understanding of the world around us. And if those interesting results can not be replicated, then we have to ask ‘why?’

Watch this space.