Incidence of Cognitive Impairment is in Decline
Rates of cognitive impairment in older people continue to decline, as noted in this study. The researchers attribute this to just about everything except improvements in medical technology, though it may well be the case that improvements in treatment and prevention of cardiovascular disease contribute to this slowed loss of cognitive function. The population is aging, however, and with an ever greater fraction of the population being old, the overall incidence of age-related disease is increasing even as individual risk falls. Further, present trends represent only incremental improvements; the development of new medical technology to treat the causes of aging is the only viable path to radical gains in health and life span.
A new nationally representative study found an abrupt decline in the prevalence of cognitive impairment among American adults aged 65 and older compared to the same age group a decade earlier. In 2008, 12.2% of older Americans reported serious cognitive problems. In 2017, the percentage had declined to 10.0%. To put this into perspective, if the prevalence of cognitive impairment had remained at the 2008 levels, an additional 1.13 million older Americans would have experienced cognitive impairment in 2017.
The study was based on 10 consecutive waves of the American Community Survey (2008-2017), an annual nationally representative cross-sectional survey of approximately half a million American respondents aged 65 and older, including both institutionalized and community-dwelling older adults. A total of 5.4 million older Americans were included in the study. In each year, respondents were asked to report if they had "serious difficulty concentrating, remembering, or making decisions." The rate of decline in cognitive impairment was steeper for women than men. Women experienced a decline of 23% over the decade, while their male peers had a 13% decline during that period.
Further analyses indicated that 60% of the observed decline in serious cognitive impairment between 2008 and 2017 was attributable to generational differences in educational attainment. Extensive previous research has concluded that every additional year of formal schooling lowers the risk of individuals eventually developing dementia. Compared to children born in the 1920s, Americans born in each successive decade had much greater opportunities to pursue post-secondary education.
However, the decline in the prevalence of cognitive problems was not entirely explained by generational differences in educational attainment, suggesting there may be other factors at play that warrant future research. The authors hypothesize several possible contributors to these positive trends, such as improvement across the generations in nutrition, declines in smoking and air pollution, and the phase out of leaded gasoline.
To this I say: "Against what benchmark?" Maybe older people in the US turn on the television and see a notable example of cognitive decline and think to themselves: "I'm not doing so bad!".