Dementia is on the decline in the U.S., as well as several other countries, especially among adults nearing retirement age.

A batch of new research reveals that dementia diagnosis has dropped 44 percent compared with diagnosis levels in the late 1970s in several developed countries, including Germany.

"This is some good news," said Dean Hartley, director of science initiatives for the nonprofit Alzheimer's Association. The studies were scheduled to be presented at this week's Alzheimer's Association International Conference, being held in Copenhagen, Denmark.

The decline is also being seen in Sweden, England and the Netherlands. One study reveals signs of progress are happening fast in Germany, however, with older adults just 25 percent more likely to be diagnosed with dementia than in 2007.

"We hope this data is saying, 'There are things we can do to change this,' " Hartley added, referring to the huge human and financial toll of dementia worldwide.

According to the Alzheimer's Association, there are 5.2 United States residents suffering from Alzheimer's disease, the most common form of dementia. Related health care costs are predicted to total $214 billion this year.

The decline in dementia diagnosis is tied to several health factors, claim researchers. The primary one may be improved cardiovascular health, according to Claudia Satizabal, a researcher at Boston University School of Medicine, who led the U.S. study.

Average blood pressure and cholesterol levels are improving and there is less risk of stroke and heart disease due to less people smoking, she noted.

Several studies have linked good heart health to lower risk of developing Alzheimer's. Oxygen to the brain is critical to staving off dementia. 

"What's good for the heart is also good for the brain," Hartley said, and researchers are also attributing the lower levels to better awareness about lowering Alzheimer's risk as well as improved education about health and lifestyle factors that impact health.

It's long been believed that activity, mental and physical, is crucial to avoiding Alzheimer's disease and other dementia ailments.

"For an individual, the actual risk of dementia seems to have declined," probably due to more education and control of health factors such as cholesterol and blood pressure, said Dr. Kenneth Langa, a University of Michigan expert on aging.