Fifth of people have gene that protects against Alzheimer’s and could one day lead to vaccine, study says

One in five people carry a genetic variant that appears to protect against Alzheimer’s and Parkinson’s, a study suggests.

Analysis of medical and genetic data from hundreds of thousands of people found that having this variant, called DR4, reduced people’s chances of developing either condition by more than 10 per cent on average.

Experts say the discovery may one day lead to a vaccine that could slow or stall the progression of these two common conditions.

An international team, led by Stanford University in California, combined databases from numerous countries to compare the incidence and age of onset of Alzheimer’s and Parkinson’s among people with the variant.

They found people with the gene were less likely to develop the condition in the first place, and those who did were diagnosed at a later age compared to those who did not have it.

Senior author Emmanual Mignot said: ‘In an earlier study we’d found that carrying the DR4 allele [variant] seemed to protect against Parkinson’s disease.

‘Now, we’ve found a similar impact of DR4 on Alzheimer’s disease.

‘That this protective factor for Parkinson’s wound up having the same protective effect with respect to Alzheimer’s floored me. The night after we found that out, I couldn’t sleep.’

The researchers also analysed data on the autopsied brains of more than 7,000 Alzheimer’s patients and found that DR4 carriers had fewer tangles of a protein called tau, as well as a later onset of symptoms, than those who did not carry the genetic variant.

They said their findings suggest that tau, an essential player in Alzheimer’s, may also turn out to play some kind of role in Parkinson’s.

The team explained that a vaccine which makes DR4 ‘work harder’ could one day be developed to delay or slow progression of Alzheimer’s and possibly Parkinson’s.

However this would only benefit the one in five people who carry the genetic variant.

Their findings were published in the journal Proceedings of the National Academy of Sciences.