A review of some recent studies by leading researchers at several medical and research centers around the U.S. has found that people are less likely to experience dementia and Alzheimer’s disease today than they were 20 years ago – and those who do may be developing it later in life.

The study authors say the research they reviewed credits the change to improvements in education levels, health care and lifestyle.

“We’re very encouraged to see a growing number of studies from around the world that suggest that the risk of dementia may be falling due to rising levels of education and better prevention and treatment of key cardiovascular risk factors such as high blood pressure and cholesterol,” says Kenneth Langa, M.D., Ph.D., a professor of Internal Medicine at the University of Michigan Medical School and a co-author of the review. “Our findings suggest that, even if we don’t find a cure for Alzheimer’s disease and dementia, there are social and lifestyle factors we can address to decrease our risk,” says Langa.

Previous studies by some of the review co-authors found that regular exercise may help delay dementia and that people with lower blood sugar levels tend to have less risk of dementia.

The researchers say that numbers of cases may still continue to grow because the number of people growing older is increasing. “The growing number of older adults in the U.S. and around the world means we will undoubtedly see a significant growth in the number of people with dementia, however the good news is they appear to be living longer without experiencing it,” says Langa, who adds that “we are seeing a positive trend that suggests that improving our physical and mental health go hand in hand with fighting off this devastating condition.”

But the researchers say other factors could impact the gains, and so people and health providers need to be vigilant. “We need to be aware that recent increases in obesity and diabetes threaten to reverse these gains, because of the impact these conditions can have on the aging brain,” says study co-author Kristine Yaffe, M.D., a professor of psychiatry, neurology, and epidemiology and biostatistics at the University of California, San Francisco and the San Francisco Veterans Affairs (VA) Medical Center.  “The obesity and diabetes epidemics are not affecting age groups most at risk for dementia—yet,” says Yaffe.

Eric Larson, M.D., MPH, executive director of the Group Health Research Institute in Seattle, Washington, and another co-author of the study, says that “to help more people avoid dementia, we’ll need to find better ways of preventing obesity—and avoiding obesity-linked health risks, including diabetes and dementia,” Larson says. Larson adds that narrowing health disparities will also be crucial, because obesity and diabetes are more common among certain racial and ethnic minorities and others who lack access to education and health care.

“As luck would have it, preventing obesity and diabetes jibes with preventing dementia,” says Larson, “[and we have to focus on] exercise, diet, education, treating hypertension, and quitting smoking.”

In 2008, Langa and Larson published one of the first studies suggesting a decline in U.S. dementia rates, using information from the U.S. Health and Retirement Study. They found that decline tracked with education and improvements in health care and lifestyle. Since then, according to the researchers, several other U.S. and European studies have confirmed the trend, and also shown that other factors that can decrease the risk of dementia include early and ongoing education, retiring later, educated parents (especially an educated mother), maintaining social activities and getting treatment for depression.

The review article on the decline in dementia was published in the New England Journal of Medicine.