Of all the new research, three studies in particular paint a stark picture of the extent to which the quality of our air can determine whether we will age with our minds intact. In one from 2018, researchers followed 130,000 older adults living in London for several years. Those exposed to higher levels of air pollutants, particularly nitrogen dioxide and fine particulate matter released by fossil fuel combustion, were significantly more likely to develop Alzheimer’s disease—the most common kind of dementia—than their otherwise demographically matched peers. In total, Londoners exposed to the highest levels of air pollution were about one and a half times more likely to develop Alzheimer’s across the study period than their neighbors exposed to the lowest levels—a replication of previous findings from Taiwan, where air pollution levels are much higher.
Another, a 2017 study published in the Lancet, followed all adults living in Ontario (roughly 6 and a half million people) for over a decade and found that those who lived closer to major high-traffic roads were significantly more likely to develop Alzheimer’s disease across the study period regardless of their health at baseline or socioeconomic status. Both of these studies estimated that around 6 to 7 percent of all dementia cases in their samples could be attributed to air pollution exposures.
Those studies from Canada and the UK are certainly intriguing. But the most compelling, and least reported on, study comes from the United States. It was also, incidentally, inspired by our previous reporting.
There is no magic shield against Alzheimer’s disease and other dementias. Supplements don’t work. Yet there is evidence that some strategies may help.
Paula Span at the New York Times writes:
Increased physical activity;
Blood pressure management for people with hypertension, particularly in midlife;
And cognitive training.
That last recommendation doesn’t necessarily refer to commercial online brain games, said Dr. Kristine Yaffe, a neuropsychiatrist and epidemiologist at the University of California, San Francisco, who served on the panel.
“It’s really the concept of being mentally active,” she said. “Find something you enjoy where you’re learning something new, challenging and stimulating your brain.”
Though the evidence to date doesn’t establish which mental workouts have the greatest impact or how often people should engage in them, “they’re not expensive and they don’t cause side effects,” Dr. Yaffe pointed out.
The blood pressure recommendation got a boost in January with the latest findings from the Sprint trial, a multisite study stopped early in 2015 when intensive treatment of hypertension (a systolic blood pressure goal of less than 120, compared to the standard 140) was shown to reduce cardiovascular events and deaths.
Dr Wyman concluded, “Apathy at baseline was related to increased risk of conversion accounting for depression severity and treatment, confirming the potential clinical importance of this neuropsychiatric symptom for assessing risk.”
In a seperate study published in the JAMA Psychiatry journal, researchers found apathy to be associated with an increased risk for incident dementia in patients with mild cognitive impairment (MCI).
These findings have high clinical relevance because patients with apathy are likely to withdraw from care. The risk for dementia among patients with apathy appears to be independent of concurrent depression, greater in the short term, and less strong with higher age and greater cognitive impairment. Apathy may be a powerful marker of increased risk for incident dementia.
A study published this week in the journal Neurology suggested that women who were physically fit in middle age were roughly 88% less likely to develop dementia (defined as a decline in memory severe enough to interfere with daily life) than their peers who were only moderately fit.
Neuroscientists from the University of Gothenburg in Sweden studied 191 women whose average age was 50 for 44 years. First, they assessed their cardiovascular health using a cycling test and grouped them into three categories: fit, moderately fit, or unfit.
Over the next four decades, the researchers regularly screened the women for dementia. In that time, 32% of the unfit women were diagnosed with the condition; a quarter of the moderately fit women did. But only 5% of the fit women developed dementia.
What these results tell us about the role exercise might play in slowing the development of Alzheimer’s is difficult to nail down. While studies like this suggest that exercising more strengthens the brain against the debilitation leading to severe dementia, definitive answers are still elusive. We don’t know, for example, the amount of exercise that makes a difference, if specific types of exercise are better than others, or whether starting exercise later in life can forestall the progression of dementia.
What we do have are solid indications that we should think of exercise and brain health in a similar way to exercise and heart health. Some of the same benefits exercise provides the heart—like improved blood flow and lower inflammation—also benefit the brain. More evidence along those lines keeps coming, further supporting the case that staying active is a better policy for brain health than the alternative.