There is encouraging news for people worried about dementia. A large study from Japan has found that individuals with low or moderate genetic susceptibility to the disease may significantly reduce their risk by maintaining healthy lifestyles and effectively managing conditions such as high blood pressure, diabetes, and obesity.
The findings suggest that genes do not entirely determine a person's future. For a large section of the population, everyday choices related to diet, physical activity, and overall health may play an important role in protecting brain function as they age.
The study, conducted by researchers from Kyushu University and RIKEN and published in Alzheimer’s & Dementia: Diagnosis, Assessment & Disease Monitoring, examined how lifestyle and health-related factors interact with genetic risk to influence dementia development.
The research is particularly relevant as dementia cases continue to rise worldwide, including in India. The number of people living with the condition is expected to nearly triple by 2050. India, with its rapidly growing elderly population, is also expected to witness a sharp increase in dementia cases over the coming decades.
Researchers analysed data from 9,605 Japanese adults aged 65 years and above. Participants were tested for the APOE ε4 gene variant, the strongest known genetic risk factor for Alzheimer's disease, the most common form of dementia.
A person can inherit zero, one, or two copies of the APOE ε4 gene variant from their parents. The study found that dementia risk increased steadily with the number of copies carried.
People with two copies of the gene faced the highest risk, with dementia rates more than ten times higher than those who did not carry the variant.
However, the findings were more encouraging for those carrying either one copy or no copies of the gene. In these groups, healthier lifestyles and better control of medical conditions were associated with a substantially lower risk of developing dementia.
Researchers assessed participants using a score based on modifiable risk factors, including health conditions and lifestyle habits that can be improved through behavioural changes or medical treatment.
Brain scans also supported the findings. Participants with healthier lifestyles and lower risk scores showed less brain shrinkage and fewer white matter lesions—changes that are commonly associated with cognitive decline and dementia.
Among those carrying two copies of the high-risk gene, however, lifestyle factors appeared to have a more limited effect. These individuals showed greater brain damage and higher dementia risk, regardless of their health profiles.
The findings underline the importance of preventive measures, particularly in countries such as India where rates of diabetes, hypertension, and obesity are rising steadily. These conditions are known to affect blood vessels and can contribute to cognitive decline later in life.
Regular physical activity, a balanced diet, blood pressure control, diabetes management, avoiding tobacco, and maintaining a healthy weight are among the measures experts recommend for preserving brain health.
“Among individuals carrying one APOE ε4 allele, as in those carrying no APOE ε4 alleles, favourable management of risk factors may help reduce the risk of dementia,” said Professor Toshiharu Ninomiya from Kyushu University’s Faculty of Medical Sciences, who led the study.
The researchers believe the findings strengthen the case for public health programmes focused on healthy ageing and better management of chronic diseases.
At the same time, they note that people carrying two copies of the APOE ε4 gene may require additional preventive and treatment approaches beyond lifestyle changes alone.
“On the other hand, for individuals carrying two APOE ε4 alleles, earlier intervention as well as new preventive or therapeutic approaches beyond lifestyle and health management may warrant consideration,” Prof. Ninomiya said.
The study offers a reassuring message: while genetic factors can increase vulnerability to dementia, many people may still be able to lower their risk through healthier living and timely management of medical conditions.
For millions facing the prospect of cognitive decline in later life, prevention may begin with simple steps taken years before symptoms appear, said the study.
