He hopes to find a cure for dementia, and will publish results in 2020

Neurologist born in the village is testing a new drug on residents

In a picturesque village in the Andes mountains, an 82-year-old woman is putting her middle aged children into nappies.

Mrs Cuartas, who lives in a small village called Yarumal, in Colombia, is forced to take care of her three children despite being an old woman herself.

Her children have been afflicted with the village's curse: something they called 'La Bobera': the foolishness.

The curse means many of the village's 5,000 residents have a genetic mutation that predisposes them to Alzheimer's disease – and most develop the condition by the time they are just 40 years old.

Doctors say 5,000 people in the village of Yarumal, Colombia (pictured), are at risk of developing early onset Alzheimer's because of a genetic mutation passed down and spread through intermarriage

Yarumal is based in the Antioquia area of Colombia. People from this area call themselves 'paisa', meaning countrymen, and the mutation which causes Alzheimer's has come to be known as the 'paisa' mutation

'To see your children like this, it's horrible, horrible.' Mrs Cuartas told The New York Times,

'I wouldn't wish this on a rabid dog. It is the most terrifying illness on the face of the earth.'

One of her sons, Dario, 55, has to be tied to a chair with blue shorts as he squirms so vigorously, shredding his nappy with his hands.

Her daughter, Maria Elsy, 61, is mute and fed by a nose tube. Previously, she had violent rages.

Maria Alsy was a nurse but started to forget her patients' medications at age 48.

Mrs Cuartas' other son, Oderis, 50, can only remember to buy one item at a time from the shop.

Many of the 5,000 villagers who live in Yarumal have inherited the mutation that pre-disposes them to Alzheimer's and intermarriage has accelerated its spread.

It was inherited from the village's Basque country ancestors, and those from the Antioquia area of Colombia now call themselves 'paisa', meaning countrymen.

WHAT IS THE YARUMAL CURSE? Many of the 5,000 villagers who live in Yarumal have inherited the mutation that pre-disposes them to Alzheimer's and intermarriage has accelerated its spread. It was inherited from the village's Basque country ancestors, and those from the Antioquia area of Colombia now call themselves 'paisa', meaning countrymen. A single parent can pass down the mutation, located on the 14th chromosome – which causes a devastating form of early-onset Alzheimer's. Those who have the mutation have a 50 per cent chance of developing Alzheimer's, sometimes as early as 32 years old. The disease begins with forgetfulness but slowly progresses to being disorientated, having delusional ideas and being aggressive. In some families, parents and children have progressed through the illness together, from memory loss to dementia. Advertisement

A single parent can pass down the mutation, located on the 14th chromosome – which causes a devastating form of early-onset Alzheimer's.

Those who have the mutation have a 50 per cent chance of developing Alzheimer's, sometimes as early as 32 years old.

The disease begins with forgetfulness but slowly progresses to being disorientated, having delusional ideas and being aggressive.

In some families, parents and children have progressed through the illness together, from memory loss to dementia.

But a neurologist named Francisco Lopera, who grew up in Yarumal, hopes there is a blessing in the village's curse.

Thirty years ago, Dr Lopera, the head of the neuroscience program at the University of Antioquia, set himself an ambitious mission: to find a treatment to prevent Alzheimer's, the most common form of dementia in the world.

'Most treatments have failed because they're administered too late. Our strategy is to intervene before the disease destroys the brain,' Dr Lopera said.

Alzheimer's disease is caused by parts of the brain wasting away.

It is not known exactly what causes this process to begin, although people with the condition have been found to have abnormal amounts of proteins called amyloid plaques, fibres and a chemical called acetylcholine in the brain.

These reduce the effectiveness of the brain's nerve calls and gradually destroying them.

Over time this damage spreads to several areas of the brain, such as the grey matter (responsible for processing thoughts) and the hippocampus (responsible for memory).

Francisco Lopera, a neurologist who grew up in Yarumal, has set himself an ambitious mission: to find a treatment to prevent Alzheimer's. He is trialling a new drug on 300 of the village's residents

For several months, Dr Lopera been testing an experimental drug on a group of 300 healthy patients aged 30 to 60 years old who have the paisa mutation.

The active molecule in his drug targets the proteins that attack the brain and lead to dementia.

The trials are part of a $100 million (£65 milion) project financed by the National Institutes of Health and Banner Research Institute in the U.S., as well as Swiss pharmaceutical group Roche.

The results are expected around 2020.

The stakes are high worldwide: more than 36 million people suffer from Alzheimer's and, without a cure, the number could rise to 66 million in 2030 and 115 million in 2050, according to the World Health Organisation.

I wouldn't wish this on a rabid dog. It is the most terrifying illness on the face of the earth

That's nearly one new case every four seconds — three times the rate of HIV infections.

'We don't know what causes Alzheimer's, but for one per cent of the cases worldwide, it's genetic in origin.

'And that opens a very important window toward finding a preventive treatment,' said Dr Lopera, who estimates 5,000 people are at risk in and around Yarumal.

At his university, a small room filled with refrigerators and formaldehyde jars holds a 'brain bank' created with organ donations from local residents — an invaluable research source.

'It was very hard for them to accept, in addition to their suffering, donating their loved ones' brains,' said Lucia Madrigal, a nurse in the neuroscience department who organises cognitive stimulation workshops for patients.

The World Health Organisation predicts 115 million people worldwide will have Alzheimer's by 2050. Pictured is a brain scan of a 74-year-old patient with the condition

'But without that social link, the scientific project could never have seen the light of day,' she said.

Herself a fit 60-something with no plans to retire, she has lived Yarumal's nightmare along with residents.

'Some say they'd rather kill themselves. Then they get sick and they forget,' she said.

Marta — an energetic, 72-year-old grandmother from Yarumal who has settled in the regional capital Medellin — said she is praying for Dr Lopera's treatment to work.

Two of her daughters, aged 43 and 47, are suffering memory loss and 'becoming small children again,' she said.

Another daughter, 53-year-old Alitee, is 'just a body' who drinks from a baby bottle.