An important new national study finds that, after adjusting for age, Americans 65 and older are less likely to get dementia than in the past. The report, published in the Journal of the American Medical Assn (JAMA) confirms previous regional studies in the US as well as recent research in Europe. The reasons for this decline in prevalence of the many dementia-related diseases are complicated, but may be related to higher educational levels. Whatever the cause, the news is positive.
Keep in mind that the research, led by Dr. Kenneth Langa of the University of Michigan, does not mean that fewer Americans will suffer from this disease. Indeed, as more of us reach old age, more of us will suffer from various forms of severe cognitive impairment. But the odds that any individual older adult will get dementia are getting longer.
In 2000, about 11.6 percent of all those 65 and older had dementia. By 2012, that had fallen to about 8.6 percent, a decline of almost one-quarter. Similarly, in 2012, about 19 percent suffered from less severe cognitive impairment, down from 21 percent 12 years earlier—a smaller decline, but still important.
Even among the very old, the decline in dementia risk was noticeable—falling from 34 percent in 2000 to a bit below 30 percent in 2012.
The study is adjusted for age and sex and was based on a large national sample of older adults called the Health and Retirement Study.
The study looked at all forms of dementia, not just Alzheimer’s Disease, the most common. Indeed, much of the decline may have occurred with vascular—or stroke-related—dementia.
What happened? These authors, like the European researchers, are not sure. But the decline in dementia rates seems somehow connected to a rise in educational attainment: The more education you have, the less likely you are to have dementia after age 65.
But why? Lifelong education and cognitive stimulation (sometimes called cognitive reserve) may prevent or delay the onset of dementia. Or it may be that better educated people have healthier lifestyles or get better health care.
The other fascinating finding is that the decline in the prevalence of dementia comes even as older adults report higher levels of obesity and diabetes, diseases that often increase the risk for strokes. However, the researchers also found that this population may be doing a better job managing these conditions, thus reducing the chances of those dementia-causing strokes. It is, as the authors acknowledge, very complicated.
What does this mean? The general trend we have seen for decade will continue: As advances in public health and medical technology help us live longer, more of us will live long enough to suffer severe cognitive decline: Remember, about 30 percent of those 85+ still will get a dementia-related condition. But for reasons we still don’t clearly understand, the chances of any one of us avoiding one of these diseases are improving, and improving pretty dramatically.