Can Actigraphy Help to Differentiate People with Narcolepsy from People with Idiopathic Hypersomnia?

Why is this study important?

Type 1 narcolepsy (T1N) and idiopathic hypersomnia (IH) are both disorders of central hypersomnolence. Even though the International Classification of Sleep Disorders, third edition, includes a finding of 11 hours of sleep during a 24-hour period (as measured by actigraphy for at least 7 days) as a criterion for the diagnosis of IH, the decision to include this criterion was based on expert consensus and not much scientific evidence. People with T1N typically have fragmented nighttime sleep, meaning that they often wake up during the night. People with IH don’t usually have fragmented nighttime sleep. The researchers involved in this study wanted to see if actigraphy, as a surrogate measure of sleep and wakefulness, could be used to identify people with T1N, people with IH, and normal control subjects (CS).

Who were the researchers?

Dr. Filardi and his colleagues were from the University of Bologna in Italy.

Who were the research subjects?

Thirty-nine patients with T1N who had never received medicine to treat their narcolepsy, 24 patients with IH who had never received medicine to treat their IH, and 30 age- and sex- matched healthy CS took part in the study. For seven days, they each wore an actigraph and kept sleep-wake diaries, in which they noted when they went to bed, went to sleep, woke up during the night, and took naps. All of the subjects with T1N were HLA DQB1*0602 positive, as were 4 subjects with IH.

What were the results of the study?

People with T1N and IH had similar levels of subjective daytime sleepiness (Epworth Sleepiness Scale [ESS] scores were 16.4 and 14.5, respectively); the control group did not have daytime sleepiness (ESS score, 4.47). All of the people in this study spent about the same amount of time in bed. The people with T1N slept significantly less than both people with IH and CS. This study included a number of other findings as well.

  1. People with T1N had the lowest sleep efficiency and had more time awake after they had initially fallen asleep, as compared with both those with IH or CS.
  2. During the nighttime, people with T1N had more awakenings and higher levels of motor activity than either of  he other groups. People with IH had fewer awakenings than people with T1N, but more than CS.
  3. During the daytime, people with either T1N or IH had significantly less motor activity and took more naps, as compared with CS.
  4. People with T1N took more naps during the day that were also longer in duration than did people with IH.
What were the authors’ conclusions?

The present study shows that actigraphic monitoring is a useful technique to objectively assess the features of sleep–wake profile of central disorders of hypersomnolence, with the main advantage of providing more naturalistic information.

Sources

Filardi M, Pizza F, Martoni M, Vandi S, Plazzi G, Natale V. Actigraphic assessment of sleep/wake behavior in central disorders of hypersomnolence.Sleep Med. 2015;16(1):126-130.

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