The number of people dying with a diagnosis of dementia has risen to almost 50%

So says a recent study conducted by researchers at the University of Michigan.  In fact, almost half of older people now die with a diagnosis of dementia.  The study results were published April 1 in JAMA Health Forum.  

While Alzheimer's disease is the sixth leading cause of death in the United States, we also wrote in Beating the Dementia Monster that the incidence of Alzheimer's disease has been declining in Western countries over the past 25 years.  This is likely a consequence of the success we've had in fighting heart disease, such as by cutting tobacco use and controlling blood pressure.  Remember, what's good for the heart is good for the brain.

But what's going on here?  Bear in mind that the study looked for people dying with a diagnosis of dementia, which is different than looking for Alzheimer's disease case rates.  All study data was drawn from Medicare records.  In the study, people could have died from cancer, heart attack, or a car accident.  But if they had a diagnosis of dementia at the time of death they would be counted as dying with that diagnosis.  That's different from dying from Alzheimer's disease or another dementia.

So what did they find?   

In a sample of Medicare fee-for-service subjects from 2004 to 2017, when adjusted for age and sex, the percentage of people who died with a diagnosis of dementia increased from 34.7% in 2004 to 47.2% in 2017.  This equates to a 36.0% increase over the 14 years.

The hypothesis of the study (what they wanted to prove or disprove) was that the frequency of an Alzheimer's disease diagnosis would increase over time through changes in diagnostic billing behavior during the time frame of the study.  This is a bit different from the headlines the study has received in the media.

So bear in mind that the study was to measure how diagnosis of dementia has varied with changes in diagnosis standards and regulations, as well as increasing awareness of Alzheimer's disease.  The coding and billing system has changed, and there is also a lot more awareness about dementia, likely as a consequence of the National Alzheimer Project Act.  They noted that in 2000, Alzheimer's disease was considered the eighth leading cause of death, while it was considered the sixth leading cause in 2018.  No one believes that reflects a change in the prevalence of the disease, only that it has been diagnosed more frequently.

The study did a couple of things to refine their results.  First, by relying on Medicare claims, their method did not consider more advanced diagnosis techniques which could more frequently identify Alzheimer's and other forms of dementia in their early stages.  This would add a lot of people like me who may have Alzheimer's disease but are not actually in dementia.  They also separately considered subjects with a single diagnosis and those with two or more diagnoses.  The data set with a single claim was intended to avoid missing cases that were under-diagnosed.  Studies often look for two diagnoses to add confidence that the patient actually had the disease in question.  And so the data set with two diagnoses (at least seven days apart) was intended to weed out spurious diagnoses.

So what's our takeaway?  As we wrote back in March, getting a handle on good Alzheimer's disease statistics is getting better, but there's still plenty of uncertainty.  Also, as awareness among physicians and the public increases, the disease is more readily recognized and our statistics improve.  Increased awareness allows families and services a greater understanding of the challenges they face as more people develop the disease.