Youngsters who watch television for long hours and stay physically inactive are at greater risk of developing Alzheimer’s disease 25 years later, according to a research presented Monday at the Alzheimer's Association International Conference in Washington, D.C. The study found that the cognitive performance of these youngsters declines significantly in midlife.

As part of the "Coronary Artery Risk Development in Young Adults Study," scientists followed more than 3,200 adults, aged between 18 and 30, for 25 years. They assessed the physical activity and television-viewing habits of the participants at least three times during the study's time frame. The team defined low physical activity as burning fewer than 300 calories in a 50-minute session thrice a week, whereas high television watching was defined as more than four hours a day, it said in a statement..

The researchers examined the memory and physical activity levels, and found that 17 percent of the participants reported a long-term pattern of sedentary lifestyle, 11 percent had a long-term pattern of high television viewing, and 3 percent reported both. The study results showed that physically inactive people and those engaged in binge television watching had twofold chances of having poor cognitive function in midlife.

“Our findings demonstrate that even early- and mid-adulthood may be critical periods for promotion of physical activity for healthy cognitive aging,” Tina Hoang, study's co-author and research associate at the Northern California Institute of Research and Education, said in the statement. “Because research indicates that Alzheimer’s and other dementias develop over several decades, increasing physical activity and reducing sedentary behavior beginning in early adulthood may have a significant public health impact.”

In 2015, an estimated 5.3 million Americans of all ages suffer from Alzheimer's disease, the most common form of dementia, according to the Alzheimer's Association. Almost two-thirds of Americans with Alzheimer's are women. Statistics also show that the number of people aged 65 and above with Alzheimer's disease will potentially rise by 40 percent in the next 10 years.

All forms of dementia will cost the United States $226 billion this year, and this is likely to increase to as much as $1.1 trillion by 2050, according to the Alzheimer's Association.