When you get old, your chance of dementia is two-thirds lower than it used to be 40 years ago, reports The Doomslayer. But there are so many more old people alive today than there were 40 years ago, that the fraction of Americans with dementia hasn’t fallen:
The risk of developing dementia increases with age, so as the US population has grown older, dementia has become more common.
However, adjusting for age reveals an opposing trend. After analyzing long-term studies on tens of thousands of elderly Americans, a group of Duke University scientists found that, over the past 40 years, the age-specific prevalence of dementia has fallen by an astounding 67 percent.
The charts from their paper (below) show the share of the population with dementia on the vertical axis, with 5-year age groups extended chronologically on the horizontal axis.
On the left, each line represents a snapshot in time. You can see that dementia has become less common in every age group since 1984.
The chart on the right presents the same data using birth cohorts, or groups of people born during a certain time period. For example, the line with orange points represents people born between 1905 and 1909. In that cohort, 23 percent of people developed dementia by their late 80s. In the 1935 cohort, only 11 percent did. For the most recent 1945 cohort, that’s expected to fall to 8 percent.
A similar trend has been documented in Europe.
In other news, happiness rates are finally improving among the young, after falling for 15 years.
Last year, nine nations eradicated a devastating disease. For example, Guinea eradicated sleeping sickness, which causes irreversible brain damage, aggressive behavior, and then death, while Niger eliminated river blindness.
Cambodia has eliminated most of its land mines, which were a leading cause of death for its youth.
Black rhinos are making a comeback, after 98% of black rhinos were killed off.
