Do Characteristics of Narcolepsy Type 1 Vary by Sex?

Few differences have been found between the male and female sexes with narcolepsy type 1 (NT1) in terms of age at onset, nocturnal age, and hallucinations, according to study results published in the journal Sleep.

Although animal models have reported some differences in narcolepsy symptomology between the sexes, there is limited information about this association among humans.

Researchers examined and compared the symptoms and neurophysiologic and biological characteristics of NT1 between the sexes in adults and in children.

Participants with untreated NT1, diagnosed according to the 3rd International Classification of Sleep Disorders (ICSD-3), at 2 European Narcolepsy Expert Centers, (Montpellier and Bologna) were enrolled in the study.

The researchers collected data on sex, body mass index (BMI), age at symptom onset, age at diagnosis, presence of hallucinations, paralysis, and medication status from all participants. They also conducted biological and neurophysiologic evaluations.

The researchers used the Epworth Sleepiness Scale (ESS) and Narcolepsy Severity Scale (NSS) to evaluate daytime sleepiness and severity of the main narcolepsy symptoms, respectively, in adults and children.

A total of 673 patients with NT1 (452 adults, 221 children) were enrolled in the study, with a mean age of 28.92 years and approximately one-third of participants being children at both centers.

After adjusting for age, center, and medication status, men vs women had a higher BMI (28.0 vs 26.7), as well as younger age-at-onset (22.92 vs 23.63 years).

Women vs men had higher ESS scores (17.75 vs 17.35; P =.06). However, PSG scores revealed that women vs men had:

• longer total sleep time (420.6 vs 395.6 min; P =.005),
• higher sleep efficiency (83.7% vs 80.6%; P =.005),
• more non-rapid eye movement (REM) sleep,
• less wakefulness after sleep onset (WASO; 68.3 vs 81.0; P =.03), and
• lower apnea-hypopnea index (AHI; 5.5 vs 10.3 h; P =.03).

Girls vs boys were older at study enrollment (13.1 vs 12.0 years; P =.02), older age-at-onset (10.1 vs 9.2 years; P =.045), and had more hallucinations (56.8% vs 36.9%; P =.002) and disrupted nocturnal sleep (60.7 vs 44.6%; P =.02). At the Montpellier center, NSS scores and severity of narcolepsy were higher in girls vs boys.

One of the main limitations of the analysis was its cross-sectional nature owing to which causality and temporal sequence of symptom development between the sexes could not be established.

“[T]his study addressed an under-researched area, examining potential sex differences in NT1 symptomatology, that could lead to more tailored treatment approaches,” the researchers concluded.

Multiple authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.