Actigraphy superior to sleep logs in narcolepsy diagnosis

Actigraphy is a simple, noninvasive method for longitudinally monitoring total sleep time (TST) over weeks or months. It is based on the idea that there is almost continual wrist motion when people are awake but only occasional wrist movements during sleep.

Wrist motion is measured with an actigraph, which looks and is worn like a small wristwatch. It contains a motion-sensitive device and a memory chip that records detected movement. Parameters such as TST, number and duration of awakenings, and daytime naps are automatically calculated and displayed.

The International Classification of Sleep Disorders, Third Edition, now includes actigraphy-derived data in the diagnostic criteria for multiple sleep disorders, and published reports suggest this data is superior to that from sleep logs. Yet actigraphy is rarely reimbursed by insurers, which limits its availability.

That led psychiatrist R. Robert Auger, M.D., and colleagues at the Center for Sleep Medicine at Mayo Clinic's campus in Rochester, Minnesota, to conduct a retrospective chart review comparing longitudinal TST data from actigraphy and sleep logs over a four-month period.

The study, which was published in 2013 in Nature and Science of Sleep, looked at 84 patients who wore actigraphs and completed sleep logs before undergoing clinical evaluations for hypersomnia or insomnia at the Center for Sleep Medicine in Minnesota. Of these, 23 patients (27 percent) failed to complete any part of their sleep logs and 8 (10 percent) had unusable actigraphy data due to device malfunction. Ultimately, complete sleep log and actigraphy data were available for 25 patients.

Among those patients, significant differences in TST were seen on weekends, with actigraphy recording a little over seven hours of sleep and sleep logs showing 8.5 hours, plus or minus 2.18 hours and 1.93 hours, respectively. Although very little deviation was seen on weekdays — 7.38 for actigraphy versus 7.72 hours for sleep logs — the logs overestimated sleep time in most cases.

Based on the results, further sleep studies were cancelled for 11 patients. In seven patients, all but one of whom complained of hypersomnia, the main reason for test cancellation was a lack of sufficient sleep as demonstrated by actigraphy.

"In our study, sleep logs clearly provided less reliable data, and the decision not to go forward with very expensive testing was based on information gleaned from actigraphy," Dr. Auger says. "Most of the patients whose tests were canceled presented with excessive daytime sleepiness. It seems painfully obvious that someone getting five or six hours of sleep a night will be tired during the day. But sometimes people don't make the connection between the amount of sleep they get and how they feel; they're not aware of how sleep deprived they are."

He says most patients referred to the center for a narcolepsy evaluation are young adults seeking a second opinion.

"We are performing the same tests as other doctors; the only thing we are doing differently is actigraphy. Adding that little piece makes all the difference. We have 20- and 30-year-olds diagnosed with narcolepsy; we put an actigraph on them and find out they are actually suffering from insufficient sleep. That can be a difficult conversation because it's often not what they want to hear. Many are hard-driving executives who don't want to be told they feel tired because they just need to sleep longer. Or they may have been consigned to a lifetime of stimulants and don't want to give that up. Whatever the case, we have the actigraphy data to back up our conclusions and recommendations."

For more information

Auger RR, et al. Total sleep time obtained from actigraphy versus sleep logs in an academic sleep center and impact on further sleep testing. Nature and Science of Sleep. 2013;5:125.