Cognitive Decline Prevention: Where We Stand Now

Date: October 24, 2010      Publication: HealthyWoman from Bottom Line      Source: JoAnn E.  Manson      Print:

Memory loss is such a frightening and frustrating aspect of aging that, of course, we want to do what we can to keep our minds sharp. So it was a devastating disappointment to many people when a recent comprehensive analysis of studies concluded that there is simply not enough scientific evidence to support many of the strategies commonly recommended for preventing cognitive decline.

The big questions: How could the results of this analysis be so contradictory to those of numerous earlier studies? And what — if anything — can and should we do now to protect our minds?

Before we tackle those questions, let’s first look at the new analysis. An independent government panel reviewed the results from 165 scientific papers published in the last 25 years and concluded in Annals of Internal Medicine (AIM) that “the current literature does not provide adequate evidence to make recommendations for interventions” aimed at preventing cognitive decline. Reasons for this conclusion…

  • Genetic factors appear to affect susceptibility to cognitive decline — and, of course, we can’t change our genes.
  • Research on strategies to prevent cognitive decline is in a state of relative infancy. There are numerous small studies with nonrigorous study designs — but few large-scale, long-term observational studies or randomized clinical trials. With many small studies of varying designs, it’s not uncommon to get inconsistent findings and thus be unable to reach a definitive conclusion. In this regard, the panel’s overall findings actually are not so surprising to me.

Still: A closer examination of the AIM report reveals some strategies that may indeed help.

Factors tentatively linked to a lower risk for cognitive decline include…

  • Avoiding certain medical conditions, such as diabetes… depression or depressive symptoms… and metabolic syndrome — a cluster of symptoms that increase risk for cardiovascular disease, including abdominal obesity, high triglycerides, high blood pressure, high blood sugar and low HDL (good) cholesterol.
  • Not smoking. People who never smoked or quit smoking appear to be 30% less likely to experience cognitive decline than current smokers.
  • Engaging in cognitively stimulating activities, such as reading, crossword puzzles and the card game bridge.
  • Regular physical activity, such as walking, biking and gardening.
  • A Mediterranean diet that emphasizes fruits, vegetables, fish and whole grains and that limits unhealthy fats… a high intake of vegetables in particular… and a high intake of marine omega-3 fatty acids, which are found in fish and fish-oil supplements. (To learn about participating in a nationwide ongoing study of marine omega-3 fatty acids being conducted by our research group at Harvard Medical School and Brigham and Women’s Hospital in Boston, see

My recommendation: Although these strategies have not yet been proven to prevent cognitive decline, it seems likely to me that many, if not all, of them will ultimately be shown to do so. Why? A significant amount of cognitive decline is related to underlying vascular disease (diseased arteries supplying the brain or heart). There is conclusive evidence that a healthy lifestyle that includes most of the above strategies can prevent a large proportion of cases of stroke and heart disease, as well as vascular risk factors, such as diabetes and high blood pressure. This vascular protection would be expected to translate into reduced cognitive risk as well. Therefore, I’m hedging my bets and still recommending — and personally practicing — these strategies for prevention not only of vascular disease but also of cognitive decline.

What appears not to help prevent cognitive decline…

The AIM report noted that, although laboratory studies and some observational studies suggest cognitive benefit for the following interventions, they have not shown benefit in available randomized trials. So, although the factors below may have other health benefits (as well as risks, in some cases), cognitive protection does not appear to be among the benefits of the following…

  • Supplements of vitamin C… vitamin E… beta-carotene… a combination of vitamins B-6, B-12 and folic acid… multivitamins… or the hormone DHEA. Most of these supplements also have failed to protect against cardiovascular disease (or cancer) in large randomized trials.
  • Menopausal hormone therapy — at least if started at age 65 or older. (We just don’t know yet whether hormone therapy helps reduce dementia risk when started closer to menopause, because in most randomized trials, the women who used hormone therapy generally were older.)
  • Nonsteroidal anti-inflammatory drugs (aspirin, ibuprofen)… cholesterol-lowering statins… or blood pressure-lowering medications (the quality of available data is particularly low for this last intervention).
  • Having an active social life and/or emotional support from friends and family.

There’s just too little data to say…

The panel found too little evidence to hazard a guess whether the following factors increase, decrease or have no effect on cognitive function…

  • Changes in caloric intake… or dietary fat intake.
  • Supplements of ginkgo biloba.
  • Having sleep apnea.
  • The presence of trace metals in the body… or toxic environmental exposures.

Bottom line: What should women make of this information? My opinion is that there is no harm and much to be gained in terms of prevention of other health problems (including diabetes, heart disease, stroke, depression and physical disability) by adhering to a healthful diet… maintaining an active, involved lifestyle… and controlling blood pressure and cholesterol levels as needed. As more rigorous studies are conducted, hopefully we will find that our efforts have also kept cognitive decline at bay.

Source: JoAnn E. Manson, MD, DrPH, is a professor of medicine and women’s health at Harvard Medical School and chief of the division of preventive medicine at Brigham and Women’s Hospital, both in Boston. She is one of the lead investigators for two highly influential studies on women’s health -- the Harvard Nurses’ Health Study and the Women’s Health Initiative. Dr. Manson is the author, with Shari Bassuk, ScD, of Hot Flashes, Hormones & Your Health (McGraw-Hill), and a columnist and advisory board member for HealthyWoman from Bottom Line.