I am of the age group where we encounter the phenomenon of people having Alzheimer’s or other forms of dementia on a fairly regular basis, either because our parents or the parents of friends or even in rare cases with people closer to our age group who succumb to early onset forms of the disease. As a result, the conversations often assume the inevitability of our own serious cognitive decline. The attitude is that it is a question of ‘when’ not ‘if’, and various strategies are bandied about as ways of delaying it.
But Judith Graham in this article suggests that all is not gloom and doom and that in fact things are getting better. It is only very late in life that dementia usually strikes and not for everyone.
New research about “cognitive life expectancy” — how long older adults live with good versus declining brain health — shows that after age 65 men and women spend more than a dozen years in good cognitive health, on average. And, over the past decade, that time span has been expanding.
By contrast, cognitive challenges arise in a more compressed time frame in later life, with mild cognitive impairment (problems with memory, decision-making or thinking skills) lasting about four years, on average, and dementia (Alzheimer’s disease or other related conditions) occurring over 1½ to two years.
Most seniors don’t have cognitive impairment or dementia. Of Americans 65 and older, about 20 to 25 percent have mild cognitive impairment while about 10 percent have dementia, according to Dr. Kenneth Langa, an expert in the demography of aging and a professor of medicine at the University of Michigan. Risks rise with advanced age, and the portion of the population affected is significantly higher for people over 85.
Langa’s research shows that the prevalence of dementia has fallen in the U.S. — a trend observed in developed countries across the globe. A new study from researchers at the Rand Corp. and the National Bureau of Economic Research finds that 10.5 percent of U.S. adults age 65 and older had dementia in 2012, compared with 12 percent in 2000.
Two years ago, Eileen Crimmins, AARP chair of gerontology at the University of Southern California’s Leonard Davis School of Gerontology, and colleagues documented this shift in the United States in research using data about adults 65 and older from the Health and Retirement Study.
In 2000, she found, a 65-year-old woman could expect to live 12.5 years with good cognition, four years with mild cognitive impairment and 2.6 years with dementia, on average. A decade later, in 2010, the period in good cognition had expanded to 14.1 years, with 3.9 years spent with mild cognitive impairment and 2.3 years spent with dementia.
For men, the 2010 figures are different: 12.5 years with good cognition after age 65 (compared with 10.7 in 2000); 3.7 years with mild cognitive impairment (the same as in 2000); and 1.4 years with dementia (compared with 1.8 years in 2010).
The reason we think that things are bad is that as people live longer, there will be more cases. The distribution is also not uniform across the population.
But gains are unequally distributed. Notably, college graduates can expect to spend more than 80 percent of their lifetime after age 65 with good cognition, according to a new study from researchers at the University of Southern California and the University of Texas at Austin. For people who didn’t complete high school, that drops to less than 50 percent.
Improvements in education and nutrition, better control of hypertension and cholesterol, cognitively demanding jobs in middle age, and social engagement in later life may all contribute to this expanded period of good brain health, the study noted.
Furthermore, the studies suggest that those with cognitive impairment can still be happy and content with their lives. This may ease the stress on caregivers who hate to think that their loved ones are unhappy in their later years.