Hearts and Minds

 In Preventive Medicine Column

 

Hearts and Minds

According to a study published recently in JAMA Internal Medicine, rates of dementia in the United States appear to be declining. The investigators used standard, validated measures of cognitive function and dementia in two groups of more than 10,000 people in the U.S. with an average age of roughly 75 in the year 2000, and again in 2012. The overall rate of dementia declined over that span from 11.6% to 8.8%.

There have been rather dire projections that with the population in the U.S. and other developed countries aging, rates of dementia would rise in tandem. Expecting dementia rates to rise and seeing them fall is simply good news. But inevitably, the whole story is not quite so simple.

This study matched its cohorts for average age. In fact, the mean age of the 2012 cohort was slightly less than the earlier group, although from a statistical perspective that were nearly equivalent. Still, the 2012 cohort certainly was not older- and it is the increase in numbers of ever-older people that was predicted to drive an increase in dementia rates. So, what if we compared a cohort of 10,000 people now with a mean age of 80, to a cohort from a decade ago with a mean age of 75?

The new study does not answer this question. The more recent study cohort did have more people over age 85 than the earlier cohort, even though the average age of the group was trivially lower, not higher. The study methods did include adjustment for age, and the decline in dementia over time remained significant. So, the good news here appears to be fairly robust- but not robust enough to preclude the feared increase in the prevalence of dementia as the mean age of the population ascends.

The basic finding of this study begs the obvious question: why? The only obvious explanation the study itself contributes is education. The more recent study cohort had significantly more educational attainment than their predecessors from a decade ago. Because this is an observational study, and not an intervention designed to establish cause and effect, it can only tell us that more years of education appear to be associated with less risk of dementia in older age.

This association is certainly plausible. Much prior research suggests that the brain, like the body, is subject to the “use it or lose it” adage. Education is brain exercise.

This finding is also promising, since education in our population is something we have the capacity to modify. The advantages to raising population-wide, average educational attainment are diverse and compelling, but that much more so if reducing the lifetime risk of dementia is in the mix. But, this finding is concerning as well. A shift in social priorities away from investments in education and the reduction in disparities that prevail in that area could certainly threaten to reverse the favorable trend.

Ironically, this paper is almost entirely silent on the topic long known to have the greatest potential to prevent dementia, namely: lifestyle. The word itself does not appear in the paper at all. Exactly one line in the discussion refers to diet and physical activity, in parentheses, when the authors note that: “Higher levels of educational attainment are also associated with health behaviors (e.g., physical activity, diet, and smoking)… which may play a role in decreasing lifetime dementia risk.”

Dementia of the Alzheimer’s type, and related vascular dementia, are generally regarded as close cousins to cardiovascular disease, and/or type 2 diabetes. Such dementia has even been called “type 3 diabetes,” referring to preferential, adverse effects of insulin resistance on the brain. Both heart disease and type 2 diabetes are overwhelmingly preventable with lifestyle. This is established by a vast aggregation of diverse research; is reflected in the health status of the world’s Blue Zone populations; and is further validated by the results of intervention at the level of a whole population over a span of decades.

The new study leaves us, as research so often does, with more questions than answers. But we may gratefully imbibe the dose of good news, even as we work to know just where it came from, and how we might go from a cup half full, to one full to the brim.

For now, though, we do know that risk factors for dementia are much the same as those for type 2 diabetes and heart disease, which in turn we know how to prevent with lifestyle. We could do a world of good for bodies and minds alike by persuading hearts and minds around the world to put to full use at long last knowledge we have long had about the primacy of lifestyle.

-fin Dr. David L. Katz;www.davidkatzmd.com; founder, True Health Initiative

Dr. David L. Katz
DAVID L. KATZ MD, MPH, FACPM, FACP, FACLM, is the founding director (1998) of Yale University's Yale-Griffin Prevention Research Center, and current President of the American College of Lifestyle Medicine. He earned his BA degree from Dartmouth College (1984); his MD from the Albert Einstein College of Medicine (1988); and his MPH from the Yale University School of Public Health (1993). He completed sequential residency training in Internal Medicine, and Preventive Medicine/Public Health. He is a two-time diplomate of the American Board of Internal Medicine, and a board-certified specialist in Preventive Medicine/Public Health. He has received two Honorary Doctorates. Dr. Katz has published roughly 200 scientific articles and textbook chapters, and 15 books to date, including multiple editions of leading textbooks in both Preventive Medicine, and nutrition. Recognized globally for expertise in nutrition, weight management and the prevention of chronic disease, he has a social media following of well over half a million. In 2015, Dr. Katz established the True Health Initiative to help convert what we know about lifestyle as medicine into what we do about it, in the service of adding years to lives and life to years around the globe.
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