Constipation precedes Parkinson's

The research record

This is the project's file for this landmark, as written and checked. Sources are listed at the end; anything not yet confirmed is marked "Not yet verified".

Who

Robert D. Abbott (Division of Biostatistics and Epidemiology, University of Virginia), H. Petrovitch, L. R. White, K. H. Masaki, C. M. Tanner, J. D. Curb, A. Grandinetti, P. L. Blanchette, J. S. Popper and G. W. Ross, working from the Honolulu Heart Program in Hawaii. Funders were not read.

What happened

Between 1971 and 1974, the Honolulu Heart Program asked 6,790 men aged 51 to 75, none with Parkinson's, how often they had a bowel movement. The men were then followed for 24 years. 96 developed Parkinson's, on average about 12 years into follow-up.

• Parkinson's incidence fell as bowel frequency rose: 18.9 per 10,000 person-years with fewer than one movement a day, versus 3.8 with more than two.
• After adjusting for age, smoking, coffee, laxative use, jogging and diet, men with fewer than one movement a day had 2.7 times the risk of men with one a day (95% CI 1.3–5.5). The excess was 4.1-fold against two a day (95% CI 1.7–9.6) and 4.5-fold against more than two (1.2–16.9).

The authors said it was unclear whether constipation is part of early Parkinson's or a marker of susceptibility.

Why it moved us toward a cure

This was the first large prospective evidence that Parkinson's begins years before the movement symptoms, and that the gut is involved. It fit the pathology in the gut plexuses (landmark 257) and Braak's suggestion that a trigger might enter through the gut (landmark 6). Trials aiming to slow the disease need people in the early window. A long prodromal (pre-diagnosis) phase with recognisable signs is what makes prevention trials conceivable.

Outcome

Advanced. Many later studies have repeated the link between constipation and later Parkinson's. It is still not specific: most constipated people never develop the disease. Only men were studied.

Sources

• Abbott et al., "Frequency of bowel movements and the future risk of Parkinson's disease", Neurology 2001;57:456–462, DOI 10.1212/WNL.57.3.456, PMID 11502913 (abstract via Europe PMC)
• American Academy of Neurology press release
• Not yet verified: funders; the ethnic make-up of the cohort; the replication studies' numbers; how many of the 96 cases were pathology-confirmed. Authors, numbers and conclusion are from the PubMed abstract.