Stress and Neurodegeneration
I have a new feature at Scientific American, describing recent research that shows how stress is linked to neurodegenerative diseases like Alzheimer's and Parkinson's.
In the past, we have feared Alzheimer's, because people rarely get better once they find out they have the disease. We watch in horror, as our aging relatives slowly become different people, donning new personalities, or forgetting who we are. And as more and more Alzheimer's drugs fail clinical trials, there is certainly a bleak outlook for new emerging treatments.
But when our environment or lifestyle factors into the disease, suddenly we regain control. For instance, thanks to years of rigorous work, we know that by cutting fats and salts from our diets, and getting lots of exercise, we can often keep heart disease at bay. Granted, we understand the effects of lifestyle on the heart much more than how it impacts the brain, but new studies are trudging forward, offering glimpses of hope:
More or less, all of the primates raised in normal size cages had the same amount of plaque. The monkeys housed in smaller cages as youngsters, on the other hand, had much more variation in their plaque level, suggesting stress may affect individuals in different ways. For some, it’s detrimental, while others appeared to take it in stride.
Clearly, these results only provide a correlative link between early life experience and measures of cognitive function, a retrospective peek that implies stress may be more than an emotional burden. But, as Plassman pointed out, we don’t know whether the brain changes the authors observed translated into true cognitive slips. Tuszynski’s team reported that they were simply not able to run tests on cognitive function for this particular experiment, because some of the older monkeys were brought to them just a few weeks before they died.
While a causal link between stress and Alzheimer’s Disease remains elusive, a bevy of research has shown that moderate stress can in fact make the symptoms of neurodegenerative diseases worse – not just in Alzheimer’s, but in animal models of Parkinson’s Disease, too.
Photo via Flickr / alancleaver_2000
References: Merrill DA, Masliah E, Roberts JA, McKay H, Kordower JH, Mufson EJ, & Tuszynski MH (2011). Association of early experience with neurodegeneration in aged primates. Neurobiology of aging, 32 (1), 151-6 PMID: 19321231
Tran TT, Srivareerat M, & Alkadhi KA (2010). Chronic psychosocial stress triggers cognitive impairment in a novel at-risk model of Alzheimer's disease. Neurobiology of disease, 37 (3), 756-63 PMID: 20044001
Smith LK, Jadavji NM, Colwell KL, Katrina Perehudoff S, & Metz GA (2008). Stress accelerates neural degeneration and exaggerates motor symptoms in a rat model of Parkinson's disease. The European journal of neuroscience, 27 (8), 2133-46 PMID: 18412632