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Counting Sleep

Illustrations by Dung Hoang

Counting Sleep (continued)

Spira first worked with actigraphy studies in California, measuring sleep disturbance using an actigraph, a small device that looks like a wristwatch with a blank face. Worn on the wrist, the actigraph contains a tiny accelerometer that measures movements as an indication of sleep and sleep disturbance. While less comprehensive than the sensors in a sleep center, actigraphy has the advantage of continuous collection for up to two weeks. "The new models are waterproof so you don't ever have to take them off," says Spira. Actigraphy data gets uploaded, run through a set of algorithms, "and that gives you all sorts of quantitative values representative of sleep parameters."

Spira pulls up sample data on the computer in his office. "These are some of the sleep parameters," he says. "Sleep efficiency, that's the percent of the time in bed that you're actually spending asleep. Here, this example is quite high—it's 95 percent basically." Sleep efficiency of under 80 percent is considered poor sleep.

Spira expects to devote the next five to 10 years to examining the link between latelife sleep disturbance and both cognition and function (which includes basic tasks such as selffeeding and bathing, as well as grocery shopping and preparing food). Knowing which aspects of bad sleep—short duration, fragmentation, etc.—lead to poor daytime functioning would help researchers develop treatment studies aimed at improving poor outcomes. "Can we prevent cognitive and functional decline? That's the hope—that we'll be able to change these unfortunate trajectories," Spira says.

Those negative trends could possibly be pushed further toward the end of life to maximize quality of life measures, such as the ability to think clearly, the capacity to take care of yourself and others, and the ability to play an active role in the community.

"We may be closer to understanding how negative consequences emerge from bad sleep," says Spira, and so, "from a public health perspective, we might better understand how to protect the health of this growing segment of our population."

Perchance to Dream

Spira has launched a field-based actigraphy study, this one looking at the role sleep might play in quality of life among older African-American adults in Baltimore. His small project is piggybacking on a larger study of the Experience Corps, a national program that has recruited 2,000 older people to tutor and mentor elementary school students in 22 cities across the country, providing literacy coaching, homework help, role models and attention.

"I wanted to see the relationship between their sleep, as measured by actigraphy, and function, and whether over the course of four months, the sleep of those in the Experience Corps program improves more than the sleep of those in the control group," he says.

It may be true, for example, that the physical activity involved in volunteering in schools every week could lead to better sleep, perhaps by increasing both physical activity and improving mood. That study will also expand the range of populations for which a sleep profile exists, notes Spira, whose project won him an award last spring through the JHSPH Faculty Innovation Fund.

Epidemiological studies such as these, coupled with ongoing advances in biostatistics, hold the potential for dramatically improving health on a wide scale, says Crainiceanu.

"Every month there's a new very large data-set study that has similar problems that we are able to address," he says. "All of them are gaining strength from the current methodological developments. Studies that include images, such as MRIs, are one of the big areas that will benefit from this research, but there are many, many other areas as well." Better ways to summarize large amounts of imaging data will help public health professionals sift through data, identify key trends and patterns more quickly, and test solutions.

"The research we have is oriented toward population level imaging and functional analysis," Crainiceanu adds, noting that
other groups are interested in their work. The challenge is to develop faster and better algorithms and a better infrastructure for these huge data sets.

The public health field is gaining new tools from the collaboration on sleep research, says Crainiceanu. The sleep findings have gained new robustness from the breakthroughs in analytical methods and led to fresh perspectives on how to look at vast data sets that are increasingly common across the field of public health. These broader benefits will be highlighted at a conference that the Bloomberg School's Department of Biostatistics is planning for 2011, about statistical methods for very large data sets, such as those generated by sleep research, genomics research or observational studies.

"New technologies and modern computing are letting us better measure health and biology," says Caffo. To more effectively use this new information, he says, we need new statistical methods.

Their collaboration, in Punjabi's poetic words, "brings new insights to old problems and helps unravel some of the complex tapestry that weaves sleep with our medical health."

Counting Sleep: Disturbing Data on the American Dream

  • 70 million: Americans who have a chronic sleep disorder or intermittent sleep problem
  • 77: Percentage of older adults who are obese who report having a sleep problem
  • 10-15: Percentage of U.S. adults who report having chronic insomnia
  • 13, 20: Percentage of Americans who reported sleeping less than 6 hours a night in 2001, and 2009, respectively
  • 20: Percentage of serious car crash-related injuries associated with driver fatigue, independent of alcohol effects
  • 1,500: Lives claimed in the 100,000 car crashes caused annually by drowsy drivers
  • $50 billion, $16 billion: Annual cost of lost productivity, and health care expenses, respectively, in the U.S. due to sleep loss and sleep disorders
  • 60-70: Percentage of Americans who do shift work who suffer from insomnia or problem sleepiness
  • 12-18 million: Estimated number of U.S. adults with sleep apnea, with more than half undiagnosed

SOURCES: NIH, National Sleep Foundation, CDC, Institute of Medicine, National Highway Traffic Safety Administration

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  • kay smolin

    palo alto 94303 11/20/2009 09:22:54 PM

    good info, need more specific fix

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