Dementia Cases Declined by 24% in US Between 2000-12, Study Reports

At a time when predictions of a dementia epidemic flourish, a recent study demonstrated that the rates have actually gone down in the U.S. — echoing findings from other studies that suggest that the idea of an epidemic is unfounded.

Forces behind the decline in dementia diagnoses are complex, and at the moment, it is difficult to conclude which contributing factors matter the most. Rising levels of education, improved health behavior, and better treatments for heart and metabolic problems are, however, top candidates, the researchers reported.

The study, “A Comparison of the Prevalence of Dementia in the United States in 2000 and 2012,” was published in the journal JAMA Internal Medicine.

Predictions of increased numbers of dementia diagnoses mostly stem from the fact that the U.S. population is aging. The Alzheimer’s Association states that the number of people living with the disease may triple through 2050.

However, recent reports indicate that, although older people make up a growing part of the population, the increase may be balanced by fewer people falling ill — at least in high-income countries. A study from England reported that, between 1991 and 2011, there were 24 percent fewer demential cases than expected, and other studies report similar numbers.

Researchers at the University of Michigan Medical School examined the number of people diagnosed with dementia in the year 2000, comparing it to cases reported in 2012, using data on more than 21,000 adults — age 65 or older — enrolled in the Health and Retirement Study.

In 2000, 11.6 percent of the participants were living with dementia. This number dropped to 8.8 percent in 2012, which translates to a relative decrease of about 24 percent.

The team compared the groups in a search for clues to the decrease. They found that in 2012, slightly fewer of the participants were women; 58.4% of cases diagnosed in 2000 were in women, compared to 56.3% in 2012.

A more important factor, the team believes, is that the 2012 group had on average one year more of education. Education is known to protect against dementia — a notion that the study confirmed. More years of education were linked to a lower dementia risk.

At the same time as dementia diagnoses were falling, the presence of conditions raising the risk of heart disease — such as high blood pressure, diabetes, and obesity — increased across the U.S.

The idea that education may counter dementia risk is referred to as “cognitive reserve” — the increased resilience to age-related brain changes brought on by cognitive stimulation.

The research team argues that increasing education levels and cognitive stimulation may also be a strategy for preventing dementia in low-income countries.

In addition to the direct effects of education on the brain, higher education levels also tend to be linked to an array of other factors that may contribute to lower dementia rates, like better use of diabetes and cardiovascular treatments.

Higher awareness of health issues and healthier behaviors, occupations that continue to stimulate cognition, and better access to healthcare also tend to go hand-in-hand with higher education levels.

So, researchers need to continue to monitor trends in dementia and contributing factors to get a clearer view of the processes most likely to impact dementia risk.