The transition from the unimpaired ability to think and remember to cognitive decline and dementia can take many trajectories and speeds, differences that scientists are only just beginning to understand. Nearly everybody experiences some cognitive losses if they live long enough, which is considered normal. Dementia, including Alzheimer’s disease, is not a normal part of aging, however, even though its incidence rises rapidly in the very old.
Cognitive decline is a complex phenomenon with multiple causes and varied manifestations. Physical changes in the brain do not fully explain matters. Autopsies show, for instance, that many older people with significant cognitive problems have few, if any, of the known hallmarks of dementia in the brain, while many of those with the hallmarks remain mentally sharp until the end. At least some of this disconnect can be explained by lifestyle factors (such as physical, mental, and social activity) that stimulate the brain’s defense mechanisms and innate resilience, thus mitigating the risk of cognitive decline.
In between normal cognition and early dementia is the gray area known as mild cognitive impairment, or MCI, which involves cognitive problems more severe than those seen with normal aging, but less severe than dementia (see "What is Mild Cognitive Impairment?" below). Depending on how MCI is defined, it’s estimated that 10 to 20 percent of Americans over 65 have the condition—far more than those who have dementia—with men affected more often than women and at earlier ages.
MCI shouldn’t be thought of as pre-dementia or early Alzheimer’s, since it doesn’t doom people to more serious memory problems. Still, anywhere from 5 to 20 percent of people with MCI progress to dementia each year, depending on its severity and on genetic, pathological (such as microbleeds in the brain), and other variables. That’s about a four-fold higher risk of dementia than for cognitively healthy people.
However, many people with MCI remain stable for years or follow a fluctuating course, while many others actually improve and revert to normal cognition, thanks to treatment of underlying problems (such as depression, hypothyroidism, vitamin B12 deficiency, cognition-impairing medications, or excessive alcohol consumption) or for unknown reasons.
Recent research offers cautious hope about both the prevention and treatment of MCI. Here’s a sampling.
What is Mild Cognitive Impairment?
How do you know if you have normal age-related memory problems or mild cognitive impairment (MCI)? Here are the clues.
Many observational studies suggest that engaging in mentally stimulating activities, starting in early to mid-life, helps preserve cognition later in life. The latest study on this focused specifically on how such activities affect the risk of MCI. Published online in JAMA Neurology in January 2017, it looked at 1,929 “cognitively normal” people (ages 70 and older) who initially underwent assessment and provided information about mental activities they had done during the past year. Over an average of four years of follow-up, 24 percent of them developed MCI.
Subsequent assessment revealed that participants who said they regularly played games, did crafts, used a computer, or engaged in social activities were 25 percent less likely to develop MCI than those who seldom did these things. In people carrying a gene (ApoE4) that increases the risk of late-onset Alzheimer’s, only computer use and social activities were associated with decreased MCI risk. While the researchers controlled for age and education (less schooling is linked with higher dementia risk), they suggested that “engagement in mentally stimulating activities may be associated with other protective lifestyle factors, such as engagement in physical exercise . . . that might in sum lead to a decreased risk of cognitive decline.”
Similar findings came from a study focusing on people over 85, published in the journal Neurology in 2015. Of the 256 people, who were cognitively normal at baseline, nearly half developed MCI over an average of four years of follow-up. The researchers found that predictors of MCI included the ApoE4 gene, depression, midlife onset of hypertension, and overall chronic (especially vascular) disease burden. The risk of MCI was reduced in people who reported undertaking artistic, craft, and social activities both in midlife and late life as well as computer use in late life. “Engaging in beneficial lifestyle activities in midlife only, or initiating them in late life, did not consistently confer benefit,” the study found.
Most well-designed studies and systematic reviews on “brain training” programs have found few, if any, lasting real-life benefits for cognitively healthy older people or those with dementia. However, computer-based training may be useful in people with MCI, suggested a 2017 analysis in the American Journal of Psychiatry. It looked at 17 clinical trials on people with MCI as well as 12 trials on those with dementia.
For people with MCI, the studies found that computer-based training was moderately effective for global cognition, memory, and attention (but not processing speed and executive function—that is, the ability to solve problems, set and meet goals, and exert self-control). In contrast, training appeared not to be beneficial for people with dementia. The researchers noted, however, that “there is insufficient data to determine whether training gains can be maintained over the long term without further training” and whether such training “can indeed delay or prevent progression of MCI to dementia.” That will require larger and longer studies.
Muscling in on MCI
Numerous studies have linked various types of exercise to a reduction in age-related cognitive decline. The most recent trial, in the Journal of the American Geriatrics Society, focused on strength training for people with MCI, ages 55 to 86. Researchers divided 100 Australians with MCI into four groups: progressive resistance training plus computerized cognitive training; resistance training plus placebo cognitive training; cognitive training plus placebo exercise (mostly stretching); or placebo exercise plus placebo cognitive training. Training was done two or three times a week; the strength training was fairly strenuous.
After six months, only people who did strength training had improvements in global cognitive function, though not memory. In addition, the greater the strength gains, the greater the overall cognitive benefits.
Best bets for brain health
Don’t hesitate to talk with your health care provider about any memory or other cognitive problems you may be having. You should have a full physical and neurological exam. However, in the absence of symptoms or signs of cognitive decline or dementia, cognitive screening is not recommended. According to the U.S. Preventive Services Task Force, there’s insufficient evidence to assess the balance of benefits and harms for routine cognitive screening in older people.
What can you do to help preserve cognition over the decades? Accumulating evidence indicates that modifying the following factors, preferably starting in midlife, can help maintain healthy cognition and, it’s hoped, slow or even reverse the progression of MCI once it develops.
- Avoid or control chronic disorders such as hypertension, diabetes, and heart disease. In general, reducing cardiovascular risk factors benefits the brain as well. However, excessive lowering of blood pressure via medication may increase cognitive decline in older people with MCI or dementia.
- Treat depression, along with anxiety and sleep disorders.
- Undertake stimulating mental, physical, and social activities.
- Eat healthfully, maintain a healthy weight, and drink alcohol only in moderation. One eating plan that may help preserve cognition is the so-called MIND diet, which is a hybrid of the Mediterranean and anti-hypertension DASH diets.
- Review any medications you take with your doctor to make sure they are not affecting your cognition. That includes OTC drugs such as antihistamines and sleep aids.
- Don’t smoke.
What about medication or dietary supplements to treat MCI? Research has been discouraging. For instance, a 2013 review in the journalCMAJ looked at eight clinical trials and found that “cognitive enhancer” drugs such as donepezil (Aricept) and memantine had no long-term benefits in people with MCI. There’s no convincing evidence that any dietary supplement (including vitamin E, according to a new Cochrane review) can improve cognitive function, unless there is a clear deficiency, as with vitamin B12.
Also see Fighting Dementia: Yes, We Can.
Published May 02, 2017