Alzheimer’s disease could be detected in its early stages via a simple and inexpensive analysis of urine samples, a study has revealed. Researchers from China found that formic acid — a chemical best known for its use in the sprayed venom of ant species, but that can occur naturally in the human body — can be found in significantly higher concentrations in the urine of people with Alzheimer’s, regardless of the disease’s severity. The discovery could pave the way for large-scale screening programs that could help detect the disease early enough to be able to treat it before it becomes irreversible.
According to the Alzheimer’s Society, in 2019 there were more than 850,000 people in the UK with dementia — equivalent to around 1 in every 14 adults aged 65 and over.
They said: “If current trends continue and no action is taken, the number of people with dementia in the UK is forecast to increase to 1,000,000 by 2025 and 1,590,000 by 2040.”
The new study was undertaken by gerontologist Yifan Wang of the Shanghai Jiao Tong University and colleagues from WuXi Diagnostics Innovation Research Institute and Fudan University in Shanghai and the Chinese Academy of Sciences in Beijing.
They said: “Alzheimer’s disease is a continuous and concealed chronic disease, meaning that it can develop and last for many years before obvious cognitive impairment emerges.
The researchers continued: “The early stages of the disease occur before the irreversible dementia stage, and this is the golden window for intervention and treatment. Therefore, large-scale screening for early-stage Alzheimer’s disease is necessary for the elderly.”
The problem with screening for Alzheimer’s is that, at present, the diagnostic methods used by doctors tend to be expensive and difficult to administer. For example, one approach relies on brain imaging via so-called positron emission tomography (PET) — but these are costly and require exposing patients to radiation during the scan.
Tests that use biomarkers, on the other hand, typically rely on the patient giving a blood sample or, worse, a sample of cerebrospinal fluid obtained via lumbar puncture. Both of these procedures can be off-putting for patients.
In contrast, urine samples are non-invasive and easy to deliver — making them well-suited for large-scale screening programs. While experts have previously identified urinary biomarkers for Alzheimer’s, none have been capable of revealing the disease in its early stages.
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In fact, the research built on previous work by the same team which focussed on the organic compound formaldehyde as a urinary biomarker for Alzheimer’s disease. Formaldehyde which is perhaps best known for its use as a tissue preservative, but is also produced naturally in small amounts in the body.
Searching for a marker that was more effective in detecting early-stage Alzheimer’s, the team turned to formic acid, which is a metabolic product of formaldehyde.
To this end, the team recruited a total of 574 people who were early healthy volunteers with normal cognition or individuals with Alzheimer’s with differing degrees of progression — ranging from subjective cognitive decline to fully-fledged disease.
Each participant was subjected to a range of psychological evaluations, and also donated blood and urine samples for analysis.
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Mr Wang and his colleagues found that, compared with the healthy control participants, all the subjects with Alzheimer’s — including those with only early-stage, subjective cognitive decline — had significantly higher levels of formic acid in their urine.
While the exact nature of the link between Alzheimer’s and formic acid is unclear, the researchers said, it appears that the compound has potential as a biomarker for the disease, even in its early stages.
Furthermore, the team also found that when they compared urinary formic acid levels with blood-based Alzheimer’s biomarkers, they were able to more accurately predict what stage of the disease the patient in question was experiencing.
The researchers concluded: “Urinary formic acid showed an excellent sensitivity for early Alzheimer’s screening. The detection of urine biomarkers of Alzheimer’s is convenient and cost-effective and it should be performed during routine physical examinations of the elderly.”
The full findings of the study were published in the journal Frontiers in Aging Neuroscience.