A new study has suggested that risk of dementia has been declining dramatically, but scientists don’t know reason behind the decline. Since the late 1970s, the chronic disorder of cognitive abilities is on the decline, as per the study featured in the New England Journal of Medicine.

For the last more than four decades, the risk of developing dementia has declined with a rate of 20% every decade. The study has released its results at a time when it was predicted that cases of dementia, also known senility, will loom in future.

It is believed that Alzheimer’s disease, a type of dementia, is going to become one of the major health problems in next one decade. More than seven million people over 60 years old may suffer and lose their cognitive abilities by 2025. If compared with today, it is an increase of about 40%. As per estimations by the Alzheimer’s Association, the progressive mental deterioration may cost 1.1 trillion by 2050.

If situation before the study is viewed, both facts by the Alzheimer’s Association can be considered true. After seeing aging of the baby boomers, it is not wrong to say that dementia cases may soon surge to an all-time high. But the new study is opposite and suggests that the disorder cases may fall in next few years.

“Can we, a couple of decades down the road, bend the arc? … Stroke used to be second leading cause of death, and now it’s the fifth. Maybe we can do this for dementia, too”, said Sudha Seshadri, a professor of neurology at Boston University School of Medicine and lead author of the study.

Seshadri and other researchers claimed the new study is true after examining data from the Framingham Heart Study. For the study, they analyzed data on more than 5,000 people from Framingham, Mass. in 1948.