Dementia? We’d rather not know: These cousins reveal why they’ve decided not to be tested 

Most of us are curious about what may lie ahead — but would you really want to know if you had a high chance of inheriting an incurable disease?

This is closer to becoming a reality for more people, with Health Secretary Matt Hancock recently announcing the NHS may sell patients their genetic data to find out what their future health may hold.

But some families are already facing this difficult dilemma. Families such as Carli Pirie’s, from Biggleswade, Bedfordshire, which includes her brother and sister and her two cousins — Jack Bradshaw, 29, and his brother Tom, 32, from Stevenage, Hertfordshire.

That’s because their family carries a rare faulty gene linked to early onset Alzheimer’s. Their mothers, Tracey and Nicole, and their maternal grandmother, Ann, all developed the condition, and the cousins have a 50 per cent chance of being affected, too.

Family ties: Carli Pirie (centre) and her 2 cousins Jack Bradshaw (right) and Tom Bradshaw (left) are running the London Marathon For Dementia Reveloution

The vast majority of Alzheimer’s cases — 99 per cent — are not thought to be caused by a single gene. While there are around 20 genes associated with a higher risk of Alzheimer’s, these are believed to have only a small effect on whether people develop it.

But in early onset Alzheimer’s, three faulty genes have been identified; if you inherit one of them, you will develop the disease.

Carli’s mum, aunt and grandmother all have one of them, called amyloid precursor protein (APP); the others are presenilin 1 and 2.

These genes are involved in the production of a protein called amyloid. If one of these genes is faulty, there can be an abnormal build-up of the protein in the brain that causes clumps or plaques, a characteristic feature of Alzheimer’s.

These ‘big lumps of sticky protein gunge up the brain and make it difficult for brain cells to communicate with each other, and eventually they kill the brain cells’, explains Dr David Reynolds, chief scientific officer at the charity Alzheimer’s Research UK.

For Carli, 31, her siblings and her cousins, witnessing their mothers’ rapid descent into dementia within just a few years has been distressing enough — both now live in care homes and barely recognise their families. But they also live with the knowledge that they have a 50 per cent chance of developing the same disease.

‘We could all find out tomorrow if we have the faulty gene or not — but so far none of us has chosen to do so,’ says Carli, a construction project coordinator who lives with partner Alex, 35, who runs an engineering company, and her daughter Olivia, ten.

‘It’s not an easy decision to make, as we have all witnessed what our grandmother and my mum and her sister have all gone through, but there’s no cure or effective treatment yet.’

Did you know? More than 5 million people suffer from the disease in the US, where it is the 6th leading cause of death.

Did you know? More than 5 million people suffer from the disease in the US, where it is the 6th leading cause of death.

Carli’s grandmother Ann developed Alzheimer’s aged just 48 in 1987 and died at 65, having not recognised her loved ones for many years.

However, at the time she was diagnosed the family were unaware the disease was hereditary — the APP gene was not discovered until 1991.

‘Everyone gets more forgetful as they get older, but when Mum began repeating herself and forgetting things in her late 40s, I had a horrible sense that history was about to repeat itself,’ says Carli.

‘She’d call me and have long conversations, then ring me back a few minutes later and tell me everything again, with no memory of the chat we’d just had.’

Carli’s mum Tracey was diagnosed with Alzheimer’s shortly afterwards, in 2010, at the age of 50, and her memory deteriorated rapidly over the next three years.

‘Mum was increasingly fearful and confused — she thought people were trying to get into the house,’ says Carli. ‘When I visited her, she would mistake me for other people. It was upsetting.’

Tracey ultimately moved into a nursing home near Carli and her sister. Still only 58, she is now bed-bound and struggles to recognise her family when they visit.

Tracey’s younger sister Nicole was diagnosed with the same condition six years ago at the age of 48, three years after her sister — the family believe their great-grandparents may also have been affected.

For the past seven years Carli has been taking part in a research project called the Dominantly Inherited Alzheimer’s Network (DIAN) at University College London, which is tracking the health of extended family members of people at risk of APP early onset Alzheimer’s with annual brain scans, plus blood, spinal fluid and cognitive tests.

Alzheimer's disease is a progressive, degenerative disease of the brain, in which build-up of abnormal proteins causes nerve cells to die

Alzheimer’s disease is a progressive, degenerative disease of the brain, in which build-up of abnormal proteins causes nerve cells to die

The researchers already know — from the results of a blood test — if Carli has the gene or not. She has now resolved to find out herself this year.

‘I changed my mind after I met someone at a DIAN conference who said she felt empowered by finding out,’ says Carli.

‘People ask me how I would live with the knowledge I was going to get Alzheimer’s in my 40s or early 50s, but I think about it every day anyway. I worry about my future. And, of course, if I am affected, there is a chance my daughter will be, too.’

Dr Amanda Heslegrave, a senior research associate at the UK Dementia Research Institute at University College London, is analysing cerebrospinal fluid (CSF) and blood samples from volunteer families with a similar history of Alzheimer’s to Carli’s.

‘We know that there are some changes that happen in the body years before symptoms start,’ explains Dr Heslegrave. ‘In studying those we definitely know will develop the disease, we can identify these changes.

‘For instance, we have identified that levels of neurofilament light, a type of scaffolding for protein, starts to rise in CSF and in the blood when there is neurodegeneration in the brain.’

It’s possible in future this chemical could be used as a biomarker to tell scientists if any drug treatments developed are having an effect.

Carli’s cousin Jack Bradshaw, a maintenance team manager with Network Rail, and his partner Nikki, 32, a lab assistant — who have two children aged six and six months — are facing the same agonising choice as Carli.


Alzheimer’s disease is a progressive, degenerative disease of the brain, in which build-up of abnormal proteins causes nerve cells to die.

This disrupts the transmitters that carry messages, and causes the brain to shrink. 

More than 5 million people suffer from the disease in the US, where it is the 6th leading cause of death.


As brain cells die, the functions they provide are lost. 

That includes memory, orientation and the ability to think and reason. 

The progress of the disease is slow and gradual. 

On average, patients live five to seven years after diagnosis, but some may live for ten to 15 years.


  • Loss of short-term memory
  • Disorientation
  • Behavioral changes
  • Mood swings
  • Difficulties dealing with money or making a phone call 


  • Severe memory loss, forgetting close family members, familiar objects or places
  • Becoming anxious and frustrated over inability to make sense of the world, leading to aggressive behavior 
  • Eventually lose ability to walk
  • May have problems eating 
  • The majority will eventually need 24-hour care   

 Source: Alzheimer’s Association

‘Obviously, I knew when I was a boy that my Nan was not quite right, but I didn’t have any idea that it was something that could be passed down until Mum was diagnosed,’ says Jack.

‘Mum had been a bubbly person — we called her Superwoman — but she suddenly became withdrawn and forgetful. She’d do things like go out to the kitchen to make a cup of tea and then forget all about it.

‘One day I got a call saying that Mum had left her front door wide open while Dad was out at work.

‘APP is quite an aggressive gene, so Mum went downhill quite rapidly. Increasingly, she couldn’t be left on her own during the day, and two and half years ago she had to go into a care home.

‘These days I don’t think Mum knows who I am,’ Jack adds.

‘One of the worst things is not only not knowing if I will be affected, but the possibility that my kids may be affected, too. When Mum was first diagnosed I think I was in denial that it would affect me, and it’s only in the last year I’ve accepted I’m at risk.’

So far Jack has chosen not to be tested — but now wants to start counselling as preparation.

‘On balance, now I think I’d rather know as I’m worrying about it anyway,’ he says.

His brother Tom, an electrician, who lives with his wife Jaymie, 30, and their two children aged 11 and six, says: ‘When I visit Mum in the nursing home I do have the fear that one day my children will be doing the same for me.

‘I haven’t had the test, either. I’ve been weighing up the pros and cons for two years but still can’t decide.’

Dr Reynolds says: ‘The difficulty is that at the moment there is no treatment for APP. This is why having the genetic test for it poses such an enormous dilemma.

‘The results can either be an enormous relief or the opposite, although some argue knowing that you have the faulty gene does allow you to plan for the future and take part in research studies where potential medicines may be given at an earlier stage when we know changes are taking place but symptoms haven’t developed yet.’

Carli, Alex, Jack, Tom and Jaymie are all running the London Marathon in April in aid of Dementia Revolution, a combined drive by Alzheimer’s Society and Alzheimer’s Research UK to fund research.

Carli admits she does ‘sometimes have bad days if I’ve seen Mum or I think too far ahead in the future, but I still have hope and can stay positive’.