Thinking Clearly About Thinking Poorly

Every Sunday morning, I do the NY Times crossword puzzle. I also do the KenKen puzzles in the daily Times, and sometimes I throw in a Sudoku for good measure. But I don’t do the puzzles to keep my mind sharp— I do puzzles because I enjoy them. A recent consensus conference convened by the National Institutes of Health found that there is no persuasive evidence that any intervention, whether mind exercises or physical exercise or anything else, can prevent dementia. A pair of new studies in the British journal, the Lancet, however, argue that the prevalence of dementia in two western European countries has fallen substantially.  What are we to make of these findings and what are the implications for each of us?

The British study measured the frequency of dementia in people over age 65 in 3 geographic areas of England in 1989-1994 and then repeated the measurements using the same questions in 2008-2011. What they found is that the prevalence of dementia in people over 65 fell from 8.3% to 6.5%—a 25% drop.

The Danish study examined both the rate of cognitive and of physical functioning in the oldest old, those 90 and up. First they studied a group of 93-year-olds, all of whom were born in 1905. Then they studied a group of 95-year-olds, all born in 1915. Despite the fact that the second group were 2 years older, 33% of them had normal scores on mental status testing, compared to 13% of the earlier cohort. The second group also did better in terms of their daily functioning (walking, bathing, feeding themselves) although formal measures of physical performance (strength, walking speeding) were the same for both groups.

A fall in the rate of dementia is certainly very encouraging. An editorial accompanying the British study concluded that lifestyle changes, such as better diet, more exercise, and less smoking, were most likely to account for the change. An editorial accompanying the Danish study concluded that changes in nutrition, exercise, and smoking behavior were very unlikely to be the explanation and suggested instead that intellectual stimulation was probably responsible for the improvement. How can they both be right?

It’s conceivable that there are different explanations for falling dementia rates in the general elderly population and in nonagenarians. It’s possible that Danes are different from Britons. More plausibly, we just don’t know what accounts for the observed decline in dementia, but it is probably related to multiple factors and not to one unique factor.

Probably the greatest medical triumph of all time is the germ theory of disease. The discovery that particular microorganisms cause specific diseases led to the discovery of antibiotics that kill bacteria—and cure disease. Penicillin and the many antibiotics discovered since have been a terrific boon to humankind, leading to the treatment of pneumonia, tuberculosis, typhoid fever, and countless other scourges. But in geriatrics, finding a single fix for the many complex conditions that afflict older people has proven far more challenging. One of the most important insights of the last few decades has been that preventing falls or confusion or other “geriatric syndromes” requires a multi-pronged approach. Whenever we look for the One Big Intervention that will do the job, we fail. Older people fall less often if their cataracts are removed and they wear shoes with good supports and they stop medications that make them faint or dizzy. Older people get confused less often while hospitalized if they don’t take sleeping pills and they talk about current events.

Today, the best strategy for staving off dementia is eating well and exercising and remaining socially engaged and doing crossword puzzles. Even before the discovery of antibiotics, improvements in sanitation and nutrition led to a steep decline in the prevalence of infectious diseases. Maybe it’s time to adopt an analogous strategy with dementia, living a generally healthier life and hoping it will somehow keep our minds functioning. We should recognize, however, that this approach will at best have a modest impact on the overall prevalence of the disease. After all, it’s great that only 33% of 95-year old Danes have normal cognition but that means 67% don’t have normal cognition. It’s terrific that the rate of dementia has fallen 25% among British people over 65, but 6.5% of them still have the diagnosis. Maybe one day we will find the magic bullet that can prevent dementia, but that day is a long way off.