The risk for a person to develop dementia over a lifetime is now 13 percent lower than it was in 2010. Incidence rates at every age have steadily declined over the past quarter-century. If the trend continues, the paper’s authors note, there will be 15 million fewer people in Europe and the United States with dementia than there are now.
The study is the most definitive yet to document a decline in dementia rates. Its findings counter warnings from advocacy groups of a coming tsunami of Alzheimer’s disease, the most common form of dementia, said Dr. John Morris, director of the Center for Aging at Washington University in St. Louis.
It is correct that there are now more people than ever with dementia, but that is because there are more and more older people in the population.
The new incidence data are “hopeful,” Dr. Morris said.
One leading hypothesis for the decline in the United States and Europe is improved control of cardiovascular risk factors, especially blood pressure and cholesterol. Nearly all dementia patients have other brain abnormalities, including blood vessel damage likely to be the result of high blood pressure.
High blood pressure seems to be most damaging in middle age, Dr. [Albert] Hofman said. Those with lower blood pressure earlier in life but higher blood pressure later tend to have reduced chances of dementia.