In the UK, Parkinson’s affects around 166,000 adults. And Parkinson’s UK writes that the disease is “on the rise” – as our population gets bigger and older, some expect that figure to reach 173,000 by 2030.
Like dementia, there is no single test that can conclusively diagnose Parkinson’s. This is a shame, because early diagnosis and treatment can improve outcomes and quality of life.
To help health professionals spot Parkinson’s risk earlier, some scientists have looked into gut changes that might reveal a higher likelihood of developing the condition.
A 2025 study found that men with a combination of three physical signs “had a 23-fold higher risk of receiving a [Parkinson’s] diagnosis in the subsequent three years” than men without.
The signs that could reveal a higher Parkinson’s risk
The study, conducted by researchers from Harvard T.H. Chan School of Public Health, Harvard Medical School and Brigham and Women’s Hospital, involved 6,108 men, who were repeatedly tested for signs linked to Parkinson’s. They were then followed over a period of 3.4years to see if any of them went on to get a Parkinson’s diagnosis.
Two measures of Parkinson’s risk were devised:
The probability of very early Parkinson’s based on the Movement Disorders Society (MDS) research criteria,The co-occurence of constipation, probable rapid eye movement sleep behavior disorder (pRBD), which can include acting out your dreams, and hyposmia (a decreased sense of smell).After a follow-up period of 3.4 years, 103 participants had been diagnosed with Parkinson’s.
Men with a very high probability of early-stage Parkinson’s disease (80% or greater) according to the MDS’ research criteria have a “21-fold higher” risk of developing Parkinson’s compared to men with a low probability.
And men with a combination of constipation, pRBD, and hyposmia faced 23 times more Parkinson’s risk than those without.
The study authors write that both measures had “comparable predictive values”.
They added: “Our study demonstrates that combinations of key signs and symptoms strongly predict future clinically manifest [Parkinson’s]”.
Researchers hope these findings will lead to better screening for Parkinson’s
Other studies have separately suggested that constipation, pRBD, and a decreased sense of smell seem to be linked to later Parkinson’s diagnosis.
Brain changes that create the motor issues associated with the condition might also affect our gut, while some think that lesions in a part of the brain called the pons, which also shows signs of damage in Parkinson’s cases, may contribute to pRBD.
Another theory suggests that the build-up of “alpha-synuclein”, which is seen in parts of the brain affected by Parkinson’s, can begin near the olfactory bulb, affecting people’s smell perception.
The combination of all three factors seems to be a stronger predictor of dementia than the presence of one sign on its own.
The paper concludes by saying that “these measures may be integrated into screening strategies to identify individuals who could be targeted for enrolment into [Parkinson’s] prevention trial”, potentially helping to spot and even help to treat symptoms in people who might otherwise go undiagnosed for longer.
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