Quantifying rigidity of Parkinson's disease in relation to laxative treatment: a service evaluation

Aisha D. Augustin, Andre Charlett, Clive Weller, Sylvia M. Dobbs*, David Taylor, Ingvar Bjarnason, R. John Dobbs

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)


Aim: To estimate whether laxatives prescribed for constipation in Parkinson's disease (PD) could moderate rigidity. Constipation predates diagnosis of PD by decades. Deposition of misfolded protein may begin in the gut, driven by dysbiosis. Successive antimicrobial exposures are associated with cumulative increase in rigidity, and rigidity has biological gradients on circulating leukocyte-subset counts. Methods: Retrospective service evaluation, in a gut/brain axis clinic, yielded an interrupted time series, relating maintenance laxative and other medication to rigidity, in consecutive outpatients identified by inclusion and exclusion criteria. Objective assessment of rigidity was used to bring greater sensitivity to change, validated against subjective gold standard (UPDRS). Results: There were 1493 measurements of torque required to extend (flexor rigidity) and flex (extensor rigidity) the forearm in 79 PD patients over 374 person-years. Both were strongly associated with UPDRS (P < 0.001 and P = 0.008, respectively). Before exhibition of laxative, flexor rigidity increased by 6% (95% CI 1, 10) per year, plateauing at −2% (−4, 1) per year after, with no shift at initiation. Change in slope was significant (P = 0.002), and manifest in those naïve to antiparkinsonian medication. The change was replicated for individual laxative classes (bulk, osmotic, enterokinetic). There was no temporal change in extensor rigidity. Limited experience with a quanylate cyclase-C receptor agonist (17 patients, 6 person-years) indicated a large and significant step down in flexor and extensor rigidity, of 19% (1, 34) and 16% (6, 24) respectively (P = 0.04 and <0.001). Conclusions: Maintenance laxative usage was associated with apparent stemming of the temporal increase in rigidity in PD, adding to indicative evidence of a continuing role of gastrointestinal dysbiosis in pathogenesis.

Original languageEnglish
Pages (from-to)441-450
Number of pages10
JournalBritish Journal of Clinical Pharmacology
Publication statusPublished - 2016

Bibliographical note

Publisher Copyright:
© 2016 The Authors. British Journal of Clinical Pharmacology published by John Wiley & Sons Ltd on behalf of The British Pharmacological Society.


  • bulk
  • dysbiosis of Parkinson's disease
  • enterokinetic and quanylate cyclase-C receptor agonist
  • gut/brain axis clinic
  • laxatives for constipation
  • objective quantification rigidity


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