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Wolfson Institute of Population Health - Barts and The London

Changes in blood counts may occur years before Parkinson’s diagnosis

A new study led by authors from the Wolfson Institute’s Preventive Neurology Unit has shown that changes in blood counts that are associated with an increased risk of Parkinson’s disease may occur years before a Parkinson’s diagnosis.

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The researchers studied the relationship between baseline blood test results (differential leukocyte count and other markers of acute inflammation) and Parkinson’s disease in 465 patients with Parkinson’s and 312,125 controls from the UK Biobank cohort. Results showed that lower lymphocytes (one of the white blood cells) were associated with increased risk of a subsequent Parkinson’s diagnosis. Further analysis using Mendelian randomization suggested that the effect of lower lymphocytes on risk of Parkinson’s may be causal, and not simply an early manifestation of the disease in people who had not yet been diagnosed. Previous research has shown that patients with a diagnosis of Parkinson’s have low levels of lymphocytes, but this is the first study to suggest that the change might occur years before diagnosis. Parkinson’s disease affects 2% of the population over age 65, but a diagnosis can only be made after symptoms appear, by which stage the disease has caused irreversible damage. Earlier detection may lead to prevention and better treatments that reduce the rate of progression.

Corresponding author, Dr Alastair Noyce said: These results may help to guide future treatment and prevention strategies for Parkinson’s disease, which currently has no cure. Whether low lymphocytes cause Parkinson’s, are a manifestation of early Parkinson’s, or that there is a common cause for both low lymphocytes and Parkinson’s are questions that must now be addressed.

The Preventive Neurology Unit is funded by Barts Charity.

Melanie P Jensen, Benjamin Meir Jacobs, Ruth Dobson, Sara Bandres-Ciga, Cornelis Blauwendraat, Anette Schrag, The International Parkinson’s Disease Genomics Consortium, Alastair J Noyce. Lower lymphocyte count is associated with increased risk of Parkinson’s disease. Annals of Neurology, 2021.