A new study published in JAMA Internal Medicine provided some much-needed good news about Alzheimer's disease and dementia. Researchers found that among Americans age 65 and older the prevalence of dementia has declined significantly--from 11.6 percent in 2000 to 8.8 percent in 2012.
The researchers uncovered some potential reasons behind the lower rates of dementia. As in other studies, this one found that people with more education are at lower risk for dementia, including Alzheimer's disease. The Framingham Heart Study, for example, showed that the number (incidence) of older participants with dementia declined by 20 percent per decade between 1977 and 2008; but the decline was seen only in those with at least a high school education.
The most likely explanation for the connection between educational attainment and dementia risk is "cognitive reserve." Studies conducted in numerous countries have shown that people with post-graduate degrees and/or those who pursue formal education throughout their lives are protected from cognitive decline, even into their 90s. This may be one reason why some older adults with accumulations of beta-amyloid plaques in their brains don't develop dementia.
Another intriguing finding of the new study is that the prevalence of dementia decreased despite an increase in risk factors such as diabetes and hypertension. One possible explanation is better medical care and patient education. The prevalence of patients seeking treatment for diabetes, hypertension, and high cholesterol also accelerated during these years, and there was a decline in vascular complications of diabetes.
Research is now being conducted to find the best ways to manage these conditions while reducing dementia risk. Many of these studies are funded by the Alzheimer's Drug Discovery Foundation (ADDF). ADDF grantee Dr. Sandra Black, working at Sunnybrook Institute and the University of Toronto, is comparing two classes of hypertension medications to determine if one prevents brain degeneration better than the other. The ADDF is also funding studies testing diabetes drugs for dementia prevention. Findings from these and other studies will help doctors prescribe drugs for common conditions such as hypertension that also reduce Alzheimer's risk.
Finally, following a healthy lifestyle over many years is also a likely contributing factor. As discussed on the ADDF's CognitiveVitality.org website, there is growing evidence that exercise, diet, social ties, and other lifestyle choices promote brain health and may prevent dementia.
It's important to note that while the prevalence (i.e., proportion of total cases in the population at a specific time) of dementia is declining, the incidence (i.e., number of new cases) of people with the disease may not be. As more people live longer and the large Baby Boomer generation ages, the incidence of people with dementia is likely to increase. Alarmingly, a new report from the British government found that dementia has now surpassed heart disease as the leading cause of death in England and Wales. This may be the case in other countries soon as Alzheimer's remains the only leading cause of death that can't be prevented or treated. To truly overcome Alzheimer's and other dementias, we need to develop safe, effective drugs as soon as possible.