Diagnosis of Alzheimer's becoming more common, but less severe

Alzheimer's disease is the most common form of dementia, affecting nearly six million Americans. Aside from the incredible toll it takes on patients and their families, the estimated total cost of care is over $400 billion. As the baby boomer generation continues to age, this economic, physical, and emotional burden is only expected to increase. In the fight against Alzheimer's, it's crucial that policymakers, researchers, scientists, and physicians are armed with forecasts based on accurate assessments of this disease.

Recently, population health scientists have described Alzheimer's as both decreasing and increasing in prevalence. This confusion may stem from the difficulty in making a definitive diagnosis. The lack of standardization in identifying patients in the data can also cause different study results.

To better understand the direction of current trends in Alzheimer's disease and other dementias, researchers from the Biodemography of Aging Unit at the Social Science Research Institute analyzed individual medical records and results of cognitive assessments commonly used to determine cognitive impairment drawn from the Health and Retirement Study data.

"An important advantage [of the study] is that it's one of the few large, nationally representative datasets to provide both repeated measurements on an individuals' cognitive status and information on diagnoses made by medical professionals through the Medicare system," said Igor Akushevich, associate research professor in the Social Science Research Institute and member of the Biodemography of Aging Unit at SSRI.

"We found that although the prevalence of Alzheimer's disease diagnoses in the Medicare population is increasing, the level of cognitive impairment in these very same individuals has been going down. This is good news and while more research is required before we can make a definitive conclusion, it likely suggests that doctors are identifying the disease at increasingly earlier stages," he said.

Researchers also identified the need for care when using pre-defined thresholds for classifying a cognitive impairment test result as dementia.

"We found that if you use a slightly different threshold, then you get a very different estimate of the trend in dementia. These estimates are very sensitive to the specific value of the threshold," Akushevich said.

The findings are in keeping with some major population trends, like the aging Baby Boomer population that's estimated at around 70 or 80 million depending on what year is used to define the generation's origin.

With Baby Boomers reaching retirement and old age, more diagnoses of age-related dementia can be expected. At the same time, these diagnoses are becoming less severe and represent less of a burden on the patient, caregivers, and health system.

"We don't have a lot of definitive knowledge about Alzheimer's disease, its biology, or the reasons for its development and progression. We've studied this condition for a very long time, but it's proving a difficult nut to crack," Akushevich said.

Because researchers know that age groups are affected differently by cognitive impairment, future work will include a thorough analysis of the age structure of the disease.

The Biodemography of Aging Unit at SSRI hosts many experts in genetics, so future research will also clarify the role of genetics in the development of Alzheimer's disease and other related dementias.