Could you have the dementia gene? Experts call for mass testing,
Middle-aged adults should be tested for a gene that could be responsible for more than 90 per cent of Alzheimer’s cases, a new study has suggested.
Scientists behind the research believe the gene, known as APOE, is associated with earlier cognitive decline, highlighting the need for midlife interventions.
Professor Wei Chen, the study’s lead author, said: ‘A growing body of research has started to explore the relationship between genetic risk factors and changes in cognitive function in the preclinical stage.
‘Our findings support consideration of AOPE e4 testing and targeted risk communication in midlife.
‘Several interventions – such as Mediterranean-style diets, structured cognitive training, and regular physical activity – show promise in attenuating cognitive decline before dementia onset.’
The APOE gene has long been recognised a major risk factor for Alzheimer’s, but scientists have found carriers of the gene show faster cognitive decline from the age of 70 than non-carriers.
The study, published in the journal JAMA Neurology, followed 4,392 Taiwanese participants, enrolled on the Health Aging Longitudinal Study.
Of this, 723 participants carried one copy of the APOE e4 gene, 33 had two copies of the gene and the remaining participants were classed as non-carriers.
Participants, who were around 68-years-old and dementia free at the beginning of the study, were followed for just over six years.
Their cognitive function was measured using a screening test called the Mini-Mental State Examination (MMSE) which tests a number of mental abilities including orientation, memory, attention and language skills and returns a score out of 30.
The higher the score, the better the cognitive function with anything lower than 23/30 indicating mild to severe cognitive impairment.
Cognitive function was measured both at baseline, during home interviews and study visits by trained professionals, and at follow up, enabling researchers to track changes in cognition over time.
On average, participants’ scores indicated good cognitive function at the start of the study, averaging a score of 27/30.
Over the course of the study, participants dropped around 0.2 points per year, totalling a reduction of 1.3 points in just over six years.
But those with the APOE e4 variant showed faster age-related cognitive decline after the age of 70, especially if they carried two copies of the gene.
These participants dropped around 2 points by the end of the study.
While still generally within the normal range, the researchers said this accelerated decline indicates a higher long-term risk of cognitive impairment as they age.
Other Alzheimer’s genetic variants, such as the APOE e2 gene which has previously been shown to have a protective effect, did not show measurable effects.
The researchers concluded: ‘Our results align with prior longitudinal studies demonstrating APOE e4-associated cognitive decline before overt dementia.
‘Approximately 17 per cent of our participants were e4 carriers who might benefit from early counseling and preventive strategies such as Mediterranean-style diets, cognitive training and regular physical activity.’
The team hope future research will evaluate the cost-effectiveness of these interventions and define optimal timing and intensity for testing and intervention.
However they acknowledged their study has some limitations including the fact the cognitive function was only assed with one screening test at two intervals which could lead to an underestimation of cognitive ability.
The findings may also not be generalisable to the general population given the small cohort – which only included a Chinese population – to demonstrate the effects of the APOE gene on healthy aging.
The researchers were also careful to stress that carrying a high-risk gene does not guarantee that someone will develop dementia.
Lifestyle and environmental factors can significantly influence risk, with smoking, poor cardiovascular health and social isolation all known to increase the likelihood of developing the memory robbing condition.
It comes following landmark research published earlier this year which found that the gene could be responsible for more than 90 per cent of Alzheimer’s cases.
Scientists behind the study suggested if the harmful influence of the gene could be neutralised, up to three-quarters – and possibly more – of Alzheimer’s cases might never develop.
Dementia is estimated to claim around 76,000 lives a year, making it the UK’s biggest killer.
Alzheimer’s is the most common form of dementia, affecting around 982,000 people in the UK. Early symptoms typically include memory problems, difficulties with thinking and reasoning, and language issues, which worsen over time.
However, experts believe that around 45 per cent of dementia cases may be preventable – or at least delayed – through lifestyle interventions and improved screening.
