SciAm: “Dementia Rates Falling Among U.S. Seniors”

Good news from Scientific America. And only 11 paragraphs long with some hypotheses on why this is happening. Short and sweet.

The percent of older US adults with dementia, including Alzheimer’s disease, declined from 11.6 percent in 2000 to 8.8 percent in 2012, a decrease of nearly a quarter, scientists reported on Monday.

The percent of seniors with dementia fell to 8.8 percent in 2012; accounting for the greater proportion of those who were 85 years or older, the decline was even greater: to 8.6 percent, the team reported in JAMA Internal Medicine.

One possible factor is education. The older adults in the 2012 group in the new study had, on average, about one year more education than the 2000 group. More education can produce greater cognitive reserve, in which people have enough backup synapses and neurons that losing some to Alzheimer’s still leaves them short of dementia. But the researchers found this didn’t explain the entire decline.

Curiously, being overweight or obese was associated with a decreased risk of dementia. Carrying excess pounds generally raises the risk of diabetes and heart disease, which are thought to increase the risk of dementia, but “late-life obesity may be protective,” wrote commentary authors Ozioma C. Okonkwo and Dr. Sanjay Asthana of the University of Wisconsin School of Medicine and Public Health. That may be especially true when people receive effective treatments for diabetes and heart disease, which also became more common with later generations.