Controversy swirled last year when a State-of-the-Science panel convened by the National Institutes of Health found insufficient evidence to recommend any health intervention to prevent Alzheimer’s disease (see ARF related news story and subsequent commentary). Many in the field argued that this conclusion sent the wrong message to the public. The Alzheimer’s Association, among others, pointed out that epidemiological evidence does support the benefits of a healthy, active lifestyle in delaying cognitive decline, and suggested that clinicians should promote this safe intervention to their patients. The continuing questions have led to a new publication in the May Archives of Neurology. The panel previously published their findings in the Annals of Internal Medicine (see Daviglus et al., 2010) as well as through an NIH statement (see Daviglus et al., 2010). In addition, researchers led by John Williams at Duke University, Durham, North Carolina, who prepared the data for the panel, published their similar but independent, conclusions as well (see Williams et al., 2010).
Panel members and Duke researchers collaborated on the new paper, which was written in response to requests from journal editors for a joint publication, said first author Martha Daviglus at Northwestern University, Chicago, Illinois. This fourth paper on the same topic reflects how hotly the issue has been debated in the field.
As have the other papers, the new paper concludes that there is not enough evidence to forge firm links between any lifestyle choice or health condition and AD risk. Nonetheless, the panel conceded that the data do show some consistent if weak associations of higher risk with diabetes mellitus (the studies did not distinguish between type 1 and type 2), hyperlipidemia in midlife, and current tobacco use. It also found an association with lower risk for healthy habits such as physical and cognitive exercise, low to moderate alcohol intake, folic acid intake, and a heart-healthy diet. Even so, the panel rated the quality of the evidence as “low” for all these associations, meaning that further research might change the conclusions. The authors stress that existing studies are inadequate to nail down these associations, and more research is urgently needed. The authors also take care to note that, “carefully designed future studies may yet establish significant associations between these same factors with prevention of AD.” They conclude, “Until more conclusive results are available, individuals should continue to aim for a physically and mentally active and healthy lifestyle and prevention of the well-known major risk factors for chronic diseases.”
The panel reviewed data from 1984 through October 2009; no newer studies were considered in this latest publication. Recent work since then has strengthened the association between physical exercise and cognitive health (see, e.g., ARF related news story on Erickson et al., 2011; ARF related news story on Erickson et al., 2010). These new studies are encouraging, Daviglus told ARF, and the benefits of exercise deserve further research. She pointed out, however, that “the panel made their recommendations and conclusions based on a body of research; it was not only a few studies.” Daviglus suggested that in the next few years, the AD field may produce enough high-quality evidence to justify revisiting this issue, and scientists might be able to make firm health recommendations at that time.—Madolyn Bowman Rogers