Thursday, 16 February 2012

Sleeping and memory

Around the world headlines are appearing saying things like: "People who have trouble sleeping twice as likely to suffer memory problems in old age".

These arise from a press release issued by the American Academy of Neurology, which itself has the title: "Trouble sleeping? It may affect your memory later on".

You could be forgiven for believing that scientists had found that if you have trouble sleeping this will affect your memory. But that is not what the study found.

The study looked at the sleep patterns of 100 people (a low number in research terms) aged between 45 and 80. Of these 25% had evidence of amyloid plaques. Whatever these may be, we are told they can appear years before the symptoms of Alzheimer's disease begin.

People who had trouble sleeping were more likely to have amyloid plaque build-up compared to people who didn't wake up as much.

The obvious question is what came first? The chicken or the egg?

Does trouble sleeping lead to amyloid plaque build-up and consequent memory problems, or does amyloid plaque build-up cause trouble sleeping?

One of the researchers' definitions of "trouble sleeping" is waking up more than five times per hour. If I was waking up five times per hour, I'd think I had a problem.

The press release quotes a researcher: "The association between disrupted sleep and amyloid plaques is intriguing, but the information from this study can't determine a cause-effect relationship or the direction of this relationship."

So it would have made as much sense to give the press release the heading: "Early stage Alzheimer's disease? This may affect how you sleep".

It's like the difference between: "Trouble sleeping? This may be bad for your back" and "Bad back? This may affect how you sleep".  Either - or both - may be true if people with bad backs have trouble sleeping.

The researchers warn against jumping to the conclusion implied by the press release headline. But people are. A comment on the first article cited above says: "So sleeping pills do more good than harm !"

Perhaps, but as a researcher says: "We need longer-term studies, following individuals' sleep over years, to determine whether disrupted sleep leads to amyloid plaques, or whether brain changes in early Alzheimer's disease lead to changes in sleep."

So sleeping pills may treat a symptom, not a cause, of early Alzheimer's.

All very "intriguing" as the researcher says.

My conclusion is I need to look beyond the headlines of science reports and rest easy.

1 comment:

  1. There is an interesting paragraph in Time which has dug further into this story. See:

    "The study is ongoing, so Ju says it’s not clear yet how the relationship works — whether amyloid starts to build up in the brain and then leads to poor sleep, or whether disrupted sleep triggers biological processes that contribute to amyloid deposits. Previous animal studies suggest that the connection is worth investigating, since mice bred to develop amyloid plaques tend to grow deposits earlier if they are sleep deprived, and animals that are given sleeping pills to help them slumber don’t get as many plaques."