Disturbed Sleep Points to Alzheimer's Disease in Hispanics ... and Maybe the Rest of Us

News-Medical.net recently reported on a study correlating sleep disturbances in American Hispanics with the development of Alzheimer's disease.  The journal Alzheimer's and Dementia published the research.  The article was "Sleep and neurocognitive decline in the Hispanic Community Health Study/Study of Latinos."

The original publication is behind the Alzheimer's and Dementia paywall, but the summary information states this:

Introduction:  "To determine if sleep-disordered breathing, daytime sleepiness, insomnia, and sleep duration predict seven-year neurocognitive decline in US Hispanics/Latinos."

And they concluded:  "Long sleep duration predicted seven-year cognitive decline."

This was a nationwide study that included 5,247 participants between the ages of 45 and 75.  According to News-Medical's interview with the lead author, they found that prolonged periods of sleep and chronic insomnia preceded declines in memory, executive function, and processing speed.  And these often signal the onset of Alzheimer's disease and other dementias.  Hispanics have a higher probability of developing Alzheimer's disease than non-Hispanic whites.

My first question is, does this indicate that controlling these factors will reduce your risk for Alzheimer's disease, or are these symptoms of a disease that is already in motion?  Or maybe both?  Certainly in Beating the Dementia Monster, we recommended doing everything you can to optimize your sleep.  We did not, however, discuss issues that might emerge from getting too much sleep.  I understand that there's a correlation between extended sleep and depression, and there is correlation between depression and Alzheimer's disease, so maybe there's a connection there.  The study says that their work points to areas for more research.

My second question is, how does these results apply to us non-Hispanics?

The researchers specifically studied the American Hispanic population with origins throughout Latin America.  It is clear from other studies that ethnicity plays a role in the development of Alzheimer's disease, so explicitly studying a single ethnic group will help us to better understand the disease.  A recognized problem with many studies is that they intend to study the population at large, but they don't consider ethnicity in their selection of subjects.  As a consequence, the study populations may have been too heavily weighted with people of Northern European ancestry.  It's increasingly clear that research should control for this variable.

On September 3 we wrote a little about the US Pointer study, which extends the work of the Finnish FINGER study.  The Finnish study provided important information correlating lifestyle with the development of Alzheimer's disease, but it studied a very homogeneous population of Scandinavians.  The US Pointer study is one of a set of similar studies around the world that should control for ethnicity.