Published on: June 29, 2012
by Alice G. Walton for Forbes:
It’s a good thing that Obamacare has passed, because it looks like more and more of us are going to need it. Alzheimer’s disease is projected to affect 80 million people in the next 20 years, and we’re only in our infancy of understanding the cause(s) of this most common form of dementia. Recent years, however, have brought to light some interesting and startling links, and researchers are beginning to understand more about how the disease spreads through the brain, and indeed how it may begin.
And while there are probably several origins, one of the triggers may be, alarmingly, something many of us experience: Stressful life events.
A new study from Britain will look further into the connection between chronic stress and the development of dementia. The concept that lifetime stressors could trigger the development of the disease, or at least facilitate the leap from mild cognitive impairment (MCI) to full-blown dementia, has gained momentum in recent years, and researchers are starting to devote more resources to exploring the relationship more fully.
“[O]ne factor increasingly implicated in the process is chronic stress,” says author of the new study Clive Holmes. “That could be driven by a big change – usually negative – such as a prolonged illness, injury or a major operation… All of us go through stressful events. We are looking to understand how these may become a risk factor for the development of Alzheimer’s. This is the first stage in developing ways in which to intervene with psychological or drug based treatments to fight the disease.”
Here’s a little bit about what we already know about the stress-dementia connection. A couple of years ago, one study reported that women who had been through significant stressors in mid-life had a significantly (65%) greater risk of developing dementia later on. The theory is that stressful events can trigger a cascade of reactions involving the stress hormones (glucocorticoids) and eventually leading to atrophy in the brain’s hippocampus – the region that is the seat of memory, and known to be most affected by Alzheimer’s disease.
Earlier work had pointed to the fact that indeed in mice, the stress hormones are linked to higher levels of amyloid precursor protein (APP) and tau protein, which is seen in Alzheimer’s and in other forms of dementia. Since humans with Alzheimer’s are known to have higher levels of the stress hormones, the authors suggest that the hormones are not a consequence of the disease, but, perhaps, a cause.
And earlier this year, a study found that when mice are subjected to stress over a period of time, they have more phosphorylated tau protein deposits in their brains. Interestingly, the study also found that if a compound is given which blocks a step in the stress cascade, the same brain changes do not occur, which could suggest a future drug target.
Finally, the other, more famous culprit in Alzheimer’s disease, amyloid-beta plaques (or “brain gunk”) have been shown to accumulate following increased brain cell activity. Specifically, there’s evidence that people who have more activity in their default mode networks (which is linked to depression, mind-wandering, and general unhappy thoughts, among others) may have increased risk for Alzheimer’s disease precisely because of this connection. This suggests, somewhat alarmingly, that even our thoughts and moods may affect our risk for dementia.
As researcher David Holtzman of Washington University told me last year, “people whose default mode networks have an average increase in activity relative to others may be at increased risk to get Alzheimer’s disease later in life and the converse may also be true (less activity in this network, less risk).” He adds that “some of the things that may be able to modify the amount of time the default mode is on are sleep and depression. So people with poor sleep or long periods of depression may be at increased risk for Alzheimer’s. This is not proved but is being actively studied.”
If you’re stressed out by the idea that stress could lead to dementia risk, don’t panic (which I’ve been doing since I heard of the connection). Looked at another way, it’s actually sort of heartening to know that this is a variable that at least we have some degree of control over. In many ways, stress is a lifestyle factor, like smoking or weight, that’s modifiable with the right tools. At any rate, this new avenue of research points to the fact that Americans’ stress level is not something to brush off as a normal byproduct of daily life. On the contrary, reducing our stress levels is something that we should take very seriously, since chronic stress can affect the ways in which our brains function in the present, and it may seriously alter our brain health in the years to come.
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