Researchers have made a groundbreaking advancement in dementia care by developing a blood test capable of forecasting a woman’s risk of developing the condition up to 25 years before symptoms manifest.

The study reveals that elevated levels of a specific protein, associated with the brain alterations typical of Alzheimer’s disease, are significantly linked to future cognitive decline in otherwise healthy women.

This innovation could empower healthcare providers to identify women at risk for dementia well before any symptoms emerge, offering a substantial lead time for intervention.

Professor Aladdin Shadyab, the lead researcher from the University of California, San Diego, emphasized the potential impact, stating, “Having such an extended lead time allows for the development of early prevention strategies and more focused monitoring, instead of waiting for memory issues to disrupt daily living.”

This advancement represents a major departure from traditional diagnostic methods, which typically depend on observing clear signs of cognitive decline after the disease has already made significant progress.

The findings, detailed in the journal JAMA Network Open, tracked 2,766 women aged between 65 and 79 years, who participated in the Women’s Health Initiative Memory Study.

At the start of the study, all women were cognitively healthy. 

Blood samples were collected at baseline and were analysed years later to look for p-tau217, a type of protein that can form plaques and tangles in the brain. 

Women with high levels of a toxic protein in their blood and on combined hormone replacement therapy may be more likely to suffer dementia, researchers say 

Everyone experiences dementia differently. Use this checklist to help you make a note of your symptoms before you talk to your GP.

This is thought to be behind the symptoms of Alzheimer’s, the most common form of dementia thought to contribute to 60 to 70 per cent of cases. 

Over the 25-years follow-up, women who developed mild cognitive impairments as well as dementia, were flagged by researchers. 

Those who had higher levels of the toxic protein in their blood at the start of the study were around three times more likely to develop dementia later in life. 

But the researchers also found that risk of cognitive decline was not the same for all women. 

Women who were 70 or older at the start of the study who had high levels of p-tau217 were more likely to show stronger signs of cognitive decline than younger women. 

The team also found that higher tau levels were more strongly associated with poorer cognitive outcomes among women with the APOE E4 gene  – a recognised risk factor for Alzheimer’s. 

High protein levels in the blood were also more predictive of dementia in women who were on combined hormone replacement therapy (HRT) – which is prescribed to help alleviate the symptoms of menopause when hormone levels drop. 

Menopause has previously been linked to a loss of brain grey matter – which is vital for mental functions, memory, emotions and movement – making women more likely to suffer dementia than men. 

Significant clumps of tau proteins can form plaques and tangle — and this is thought to be behind Alzheimer’s symptoms

Interestingly, whilst both white and black women with higher p-tau217 levels were found to be an increased risk of developing dementia, the protein was not linked to mild cognitive impairment in black women.

 The researchers speculated this could be because mild cognitive impairment may be caused by different health problems in this group, such as vascular disease which restricts blood flow to the brain. 

Cognitive tested used to diagnose the condition also may now work equally as well for all populations. 

The team concluded: ‘Our findings suggest a potential moderating role of age, race APOE E4 and hormone therapy in the associations between p-tau217 and cognitive outcomes.

‘Blood-based biomarkers like p-tau217 are especially promising because they are far less invasive and potentially more accessible than brain imagine or spinal fluid tests.

‘This is important for accelerating research into the factors that affect risk of dementia and for evaluating strategies that may reduce risk.’ 

But, Prof Shadyab added: ‘Ultimately, the goal is not just prediction, but using that knowledge to delay or prevent dementia altogether.’ 

Experts who were not involved in the study have welcomed the findings, highlighting the potential risks of hormone replacement therapy. 

‘This is a well conducted observational study showing that race, older age and use of hormones replacement therapy can all affect how effective a blood test is at predicting cognitive decline and dementia in women,’  Prof Tara Spires-Jones from the University of Edinburgh said.

‘A strength of this study was looking at HRT use, with authors finding a stronger association of the p-tau217 blood test with dementia in people who took oestrogen plus progestin but not oestrogen alone.

‘Understanding how age, race and HRT might influence the interpretation of this type of blood test is important for future clinical trials.’

However, she added that the study has a number of limitations to consider, including the fact that the data cannot explain why HRT influences the effectiveness of blood tests and potential dementia risk. 

Neurologists from the University of Oxford agreed, labeling the findings ‘impressive’ whilst stressing that not everyone with higher levels of this protein go one to develop dementia, meaning a positive test does not guarantee dementia. 

Dr Sheona Scales, Director of Research at Alzheimer’s Research UK, similarly welcomes the findings. 

‘Women are twice as likely to be affected by dementia, but we do not understand why there is this difference,’ she said. 

‘As it stands today, these blood tests are fast becoming a powerful tool as part of a standard dementia diagnosis assessment. But we are still learning about how these tests work, especially in people who don’t have the signs and symptoms of mild cognitive impairment or dementia, so they are not currently a standalone test.

‘While the findings are promising, more research is needed before these tests could be used to reliably predict dementia in routine healthcare.’