Genes Impact How Much Brain Power You’ll Lose By Old Age

by Elizabeth Nolan Brown for BlissTree:With Alzheimer’s and dementia increasing and baby boomers aging, it seems everyone from researchers to video game makers are focused on brain health like never before. And a lot of the results are encouraging: Turns out, ‘cognitive decline’ isn’t totally the crapshoot many once thought it was. A nutritious diet, keeping active, hormones and even a college degree can influence your chances of staying sharp while you age and avoiding Alzheimer’s disease and dementia. But new research indicates that genes do not have an impact on how much brain power you'll lose over your lifetime and to a much higher degree than ever before estimated.It turns out, almost a quarter of the changes to our intelligence levels as we age may be genetic. The study, published inNature, suggests that genes may partly explain why some people’s intelligence age better than others.Most research on genes in the past was done in studies of identical or fraternal twins. But new DNA-based techniques allow scientists to study unrelated people. The Wall Street Journal explains:

The scientists behind the Nature paper were able to do their analysis thanks to an unusual database maintained in Scotland: records from 1,940 unrelated individuals whose intelligence was measured first at age 11 and then again at age 65, 70 or 79. It is rare for researchers to have access to intelligence data for a group of people from both childhood and old age. The participants also provided blood for DNA analysis.

With these separate pieces of information, the researchers used a new statistical technique to seek out any associations between genes and how intelligence levels might have shifted over the years.

Note that they didn’t study how genetics affect overall intelligence level; it’s a view of how genetic variants affect people’s rate or amount of cognitive decline (people tend to get a bit huffy when discussing intelligence and genetics, so the distinction’s important, I think).“It is very rare to have an estimate of the genetic contribution to lifetime cognitive change,” University of Edinburgh psychologist and lead researcher Ian Deary said. Which makes this study pretty darn neat.However … even if genes contribute to long-term brain health more than expected, they still only account for 24% of the equation. That means 76% of the way your brain ages is influenced by environmental factors, like diet, exercise, education, stress and exposure to toxins. I kind of like the headline for the Daily Mail's story on this study: Slowing down a bit? Don’t blame your genes – your lifestyle is key to staying alert into old age. [Mark this date, because I think it may be the first time I've ever positively mentioned a Daily Mail article here.] The differences between this article and the WSJ’s coverage is pretty striking, actually.Ultimately, both narratives are positive, though. It’s sort of self-evidently empowering to know that choices we make and the habits we do (or don’t) cultivate really can help our brains avoid the horribleness of dementia or Alzheimer’s (anyone who’s ever had a close relative with severe dementia knows—it’s heartbreaking). But discoveries about the genetic components of brain health shouldn’t be taken negatively. Figuring out which genes contribute to degenerative diseases go a long way toward treating or preventing those diseases. The more we know about nature and nurture, the better for our future brain health.